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CONTENTS
Vol. XVII No. 7 July 2015
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Microbes or microorganisms are those organisms which are not visible to naked eye and can be observed only with the aid of a microscope because they have a size of 0.1 mm or less. Microbes belong to diverse groups of organisms including bacteria, fungi, protozoa, and microscopic plants. Viruses, viroids and prions are also included amongst microbes. Most of the microbes can be grown on nutritive media where they form colonies, e.g., bacteria, fungi. The colonies can be seen with naked eyes.
Microbes are ubiquitous in our environment i.e., they are found in the soil, mud, water, air, body of other organisms, food products, clothes, shoes, optical instruments, nails, skin, etc. They may occur even at places where no other organism can possibly exist, e.g., inside thermal vents or geysers with temperature 100°C, under several
metres thick snow where temperature is several degrees below 0°C, highly saline or extremely acidic environment, etc.
The microorganisms influence man in several ways. Microbes are known to cause various diseases in man and other organisms and for deteriorating food, clothing, furniture, machinery etc. But some of their activities are useful for us. Such activities include antibiotic production, production of dairy products and fermented beverages, sewage treatment etc. Useful activities of microbes can be discussed under several heading as discussed ahead.
microbes in household products
In our household we use a variety of microbes or products obtained from them. Curd, cheese, bread etc., which are part of our daily lives, are obtained by microbial activity.
dairy products
Dairy products include curd, yoghurt, butter milk, cheese etc.
microbes in human welfare
The content for PMT Biology is very vast and does not allow students to engage in inquiry and develop meaningful knowledge. An essential topic for PMT is presented here to enable students grasp the topic, analyse the type of questions appearing in PMTs, and score HIGH.
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curd
The starter or inoculum used in preparation of milk products containing millions of lactic acid bacteria (LAB) like Lactobacillus are added to skimmed or cream milk at a temperature of about 40°C or less. They convert lactose sugar of milk into lactic acid. Lactic acid causes coagulation of milk protein casein. Milk is changed into curd.
Besides the conversion of milk into lactic acid, the LAB also improve its nutritional quality by increasing vitamin B12. Curd is more
nutritious than milk as it contains a number of vitamins and organic acids. LAB present in curd also check growth of disease causing microbes in stomach and other parts of digestive tract. Indian curd is used either as such or in other forms such as mattha, chhach or lassi.
Yoghurt and butter milk
Yoghurt is produced by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricus. Butter milk is
acidulated product which is formed by inoculating skimmed milk with starter culture of Streptococcus cremoris, S. lactis, Lactobacillus acidophilus, Leuconostoc species at 22°C for 18 hours.
cheese
Cheese is known to be the oldest food item in which microbes are used. There are two groups of cheese, fresh or unripened cheese and ripened cheese. The unripened cheese are made up of milk coagulated by acid or high heat e.g., cottage cheese, while ripened cheese are made through lactic acid bacterial fermentation and coagulated by an enzyme preparation.
A large number of microorganisms play a role in the ripening process and different varieties of cheese are obtained depending upon the microorganisms used in production. The CO2 producing culture of Propionibacterium sharmanii is essential for
giving swiss cheese its eye or holes, and flavour. Roquefort cheese uses Penicillium roqueforti while camembert cheese employs P.camemberti for ripening.
Soft cheese
• is ripened by the enzymes from yeast and other fungi that grow on the surface.
Hard cheese
• is ripened by lactic acid bacteria which grows throughout the cheese, die, autolyse and release hydrolytic enzymes.
The
• semisoft cheese is ripened by proteolytic and lipolytic organisms which soften the curd and give it a flavour.
dough for making food items
Numerous food items such as ‘dosa’, ‘idli’, ‘jalebi’ and ‘bread’ are prepared by fermentation process in which one or more kinds of microbes are used.
Dosa, uppma and idli are fermented preparation of rice and black gram. The ‘dough’ which is used for making dosa and idli is
allowed to ferment overnight for 10 to 12 hours. The bacteria, which come from atmosphere (particularly Leuconostoc mesenteroides, Streptococcus faecalis) cause fermentation so that the dough increases in volume and gets sour. Increase in the volume of dough is due to carbon dioxide gas (CO2) that is released as a result of fermentation.
Bread is made from flour obtained by grinding cereal grain usually wheat. Selected strains of Saccharomyces cerevisiae grown on molasses are used as baker’s yeast. A small quantity of yeast is added to wheat flour and kneaded. The kneaded flour is kept at warm temperature for a few hours. It swells up. The phenomenon is called leavening.
Leavening is caused by secretion of three types of enzymes by yeast. They are amylase, maltase and zymase. Amylase causes breakdown of a small quantity of starch into maltose sugar. Maltase converts maltose into glucose. Glucose is acted upon by zymase. Zymase is a complex of several enzymes of anaerobic respiration which brings about fermentation.
Fermentation of glucose mainly forms ethyl alcohol and carbon dioxide. The two cause swelling or leavening of dough. The leavened dough is baked. Both carbon dioxide and ethyl alcohol evaporate making the bread porous and soft.
single cell proteins
A relatively new food source is single cell protein (SCP). Its production began in the late 1960s. The term refers to protein obtained from the large scale growth of microorganisms such as bacteria, yeasts and other fungi, and algae. The protein may be used for human consumption or animal feed. It may also be a useful source of minerals, vitamins, fats and carbohydrates. The common SCP are obtained from Spirulina, yeast and Fusarium graminearum. SCP is rich in high quality protein but poor in fat.
other household products
Coconut water is fermented to produce a refreshing drink called toddy. It is a traditional drink in some parts of Southern India. The term toddy is also applied to sweet exudation got by tapping unopened spadix of coconut. Palm sugar or jaggery is produced by
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boiling it. The exudation is rich in natural yeasts which bring about its rapid fermentation to produce an intoxicating alcoholic drink.
Arrack is obtained by distillation of fermented toddy. If allowed to ferment for more than 24 hours, toddy becomes unpalatable as
alcohol is changed to vinegar.
Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods. A most popular type of fermented food is produced from soyabeans called tempeh kedele. It is important source of vitamin B12. Tofu and sofu are also obtained from soyabeans.
microbes in industrial products
Fermentative activity of microbes is used industrially to obtain a number of products. The two common ones are beverages and
antibiotics. The container, where fermentation is carried out, is called fermentor or bioreactor.
Fermented beverages
Yeast species used in alcoholic fermentation are Saccharomyces cerevisiae (brewer’s yeast), S. ellipsoidens (wine yeast), S. sake (sake yeast) and S. pireformis (ginger beer/ale yeast).
The nutrient medium is barley malt for beer, fermented rye malt for gin, fermented rice for sake, cashew-apple for fenny, potato for vodka, fermented cereals for whisky, fermented molasses for rum and fermented juices for wines and brandy.
baker’s and brewer’s yeasts
The yeasts are basically of two types-baker’s yeast and brewer’s yeast. The selected strains of Saccharomyces cerevisiae, used in baking industry to bring about desired changes in flavour and texture of the baked products, are sold as baker’s yeast. They are available in the form of powder or cakes. The yeasts, which are used in the brewing industry for the preparation of alcoholic drinks, are collectively called brewer’s yeast.
Different kinds of alcoholic beverages are produced by using different brewer’s yeast and the fermenting medium. Beer and wine are
undistilled beverages whereas whisky, rum, gin, brandy, vodka and fenny are distilled beverages. Distilled beverages are called
‘hard liquors’ as they contain higher percentage of alcohol.
Beer is an undistilled product of grain-mesh fermentation brought about by Saccharomyces cerevisiae and S. carlsbergensis. Wine is an undistilled product of fruit-juice fermentation brought about by Saccharomyces ellipsoideus. Fermentation can be done using three different methods:
(i) Batch culture : In the batch culture, the conditions are set up and not changed from outside once the fermentation starts;
for example, no more nutrients are added. This is why the process is described as a closed system. The process is stopped once sufficient product has been formed. The contents of the fermenter are then removed, the product isolated, the microorganism discarded and the fermenter is cleaned and set up for a fresh batch.
(ii) Continuous culture : Continuous culture involves continuous long-term operation over many weeks, during which nutrient
medium is added as fast as it is used, and the overflow is harvested. Although this is closer to the situation in natural environments, such as the gut, continuous culture has found only limited application. However, it is used for the production of single cell protein where a large biomass of cells is required.
(iii) Fed batch culture : This is a compromise between the two systems. With fed-batch culture more control of the process
is involved than with batch culture. The period of growth is extended by adding nutrients at low concentrations during the fermentation, and not adding all the nutrients at the beginning. One advantage of this is that the rate of growth can be regulated to keep pace with the rate at which oxygen can be supplied. The process is commonly used to produce yeast cells for the baking industry.
antibiotics
The term ‘antibiotics’ was coined by Waksman (1942). Antibiotics (Fr. anti = against; bios = life) are chemical substances secreted by some microorganisms which inhibit the growth and development of other microbes. Antibiotics are obtained from eubacteria, fungi and actinomycetes. Most of them are produced by actinomycetes, specially the genus Streptomyces.
The study of antibiotics began by the discovery of penicillin in 1929, when Alexander
Fleming proved that the filtrate of a broth culture of Penicillium notatum has antibacterial
properties in relation to Gram-positive bacteria. In 1940, Ernest Chain and Howard Florey commercially extracted a relatively stable preparation of penicillin. The chemical was extensively
used in treating wounded American soldiers in world war II. Fleming, Chain and Florey were awarded Nobel Prize in 1945. Waksman and Woodruff isolated actinomycin in 1941 and streptothricin in 1942.
Waksman and Albert (1943) and Waksman (1944) discovered streptomycin. Burkholder (1947) isolated chloromycetin. Over 7000 antibiotics are known.
Table: Some common antibiotics, their source and action.
Antibiotics Source Action
Chloramphenicol S. venezuelae Typhoid, whooping cough
Erythromycin S. erythreus Diphtheria
Chloromycetin S. lavendulae Pneumonia
Streptomycin S. griseus Meningitis, Pneumonia, TB
Bacitracin Bacillus licheniformis Syphilis, Lymphonema
production of antibiotics
Various steps involved in the production of an antibiotic have been summarised in the table given below.
bioactive molecules
Cyclosporin - A is an important bioactive chemical produced by the fungus Trichoderma polysporum. It is an 11-membered cyclic
oligopeptide. This chemical is used as an immunosuppressive agent in organ transplantation.
Statin is produced by yeast Monascus purpureus. It is used as blood cholesterol lowering agent by acting as a competitive inhibitor
of enzyme for cholesterol synthesis. Some microbes are used to obtain organic acids, enzymes etc.
organic acids
Microbes are also used for commercial and industrial production of certain organic acids. The first organic acid produced through microbial fermentation was lactic acid (Scheele, 1789). Some other common organic acids produced through microbial activity are acetic acid, citric acid and butyric acid.
There are mainly two steps in acetic acid or vinegar production. In the first stage yeast converts sugar into ethanol anaerobically while in the second step ethanol is oxidised to acetic acid aerobically by Acetobacter aceti. This process is called acetification. This organic acid is employed in pharmaceuticals, colouring agents, insecticides, plastics, etc.
Citric acid is obtained through the fermentation carried out by Aspergillus niger and Mucor species on sugary syrups. Yeast can also
be employed, provided its nutrient medium is made deficient of iron and manganese. Citric acid is employed in dyeing, engraving, medicines, inks, flavouring and preservation of food and candies.
Lactic acid fermentation is carried out by both bacteria (e.g., Streptococcus lactis, Lactobacillus species) and fungi (e.g., Rhizopus). Clostridium acetobutylicum is the bacteria that is used for production of butyric acid.
enzymes
Enzymes are proteinaceous substances of biological origin which are capable of catalysing biochemical reactions without themselves undergoing any change.
Streptokinase (Tissue Plasminogen Activator or TPA) is an enzyme obtained from the cultures of some haemolytic streptococci.
It has fibrinolytic effect. Therefore, it helps in clearing blood clots inside the blood vessels through dissolution of intravascular fibrin.
Pectinases are obtained commercially from Byssochlamys fulva. Along with proteases, they are used in clearing of fruit juices. Other
uses are in retting of fibres and preparation of green coffee.
Lipases are lipid dissolving enzymes that are obtained from Candida lipolytica and Geotrichum candidum. Lipases are added in
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microbes in sewage treatment
Sewage is waste water having food residues, animal and human excreta, detergents, discharges from commercial and industrial
establishments and pathogenic microbes etc. Sewage poses many harmful effects such as:
It results in dissemination of water-borne diseases caused by microorganisms. –
It may cause depletion of dissolved oxygen in water. Reduction in oxygen availability may kill aerobic aquatic organisms. –
Untreated sewage produces offensive odour. –
Thus sewage treatment is essential for reducing harms done by it. Whenever untreated sewage is disposed into natural waters such as streams, ponds, lakes, etc., the normal amount of dissolved oxygen present in water, gets quickly utilised by microorganisms as a result of oxidation of organic matter present in sewage. Biochemical oxygen demand (BOD) is increased. BOD represents the amount of dissolved oxygen that would be consumed if all the organic matter in one litre of water were oxidised by microorganism (at 20°C). It is an indicator of water quality. Thus, high value of Biochemical Oxygen Demand (BOD) means the water is highly polluted by organic matter. Low value of BOD means the water is either normal or less polluted by organic matter.
Sewage water can be purified by passing it through sewage treatment plants with the action of heterotrophic microorganisms. A sewage treatment plant separates solids from liquids by physical processes and purifies the liquid by biological processes.
There are two stages of this treatment; primary or physical treatment and secondary or biological treatment.
primary treatment
It removes floating and suspended solids from sewage through two processes: filtration and sedimentation. First, floating matter is removed through sequential filtration with small pore filter progressively. The filtrate is kept in large open settling tanks where grit (sand, silt, small pebbles) settles down.
The sediment is called primary sludge while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. It is subjected to composting or land fill where anaerobic digestion removes the organic matter.
secondary treatment
There are several methods of secondary treatment, e.g., oxidation tanks, trickling filter, and activated sludge system.
In activated sludge system, the primary effluent is taken to aeration tanks. A large number of aerobic heterotrophic microbes grow in the aeration tank. They form flocs. Flocs are masses of bacteria held together by slime and fungal filaments to form mesh like structures. The microbes digest a lot of organic matter, converting it into microbial biomass and releasing a lot of minerals.
As the BOD of the waste matter is reduced to 10-15% of raw sewage, it is passed into settling tank. Thus secondary treatment is more or less biological. The sediment of settling tank is called activated sludge. A part of it is used as inoculum in aeration tank. The remaining is passed into a large tank called anaerobic sludge digester. Anaerobic microbes digest the organic mass as well as aerobic microbes of the sludge. They are of two types, nonmethanogenic and methanogenic.
Methanogenic bacteria produce a mixture of gases containing methane, H2S and CO2. The mixture called biogas is inflammable
and is a source of energy. The spent sludge can be used as manure or part of compost.
Finally the treated sewage effluent is subjected to chemical treatment for disinfection before releasing it into natural water bodies like rivers and streams.
river action plan
Before 1985 very few cities and towns had sewage treatment plants. The municipal waste water was discharged directly into rivers resulting in their pollution and high incidence of water borne diseases. In order to protect the major rivers of India from sewage pollution, the Ministry of Environment and Forests, has initiated development of sewage treatment plants under the National River Conservation Authority, e.g., Ganga Action Plan (GAP), Yamuna Action Plan, Sutlej Action Plan, Gomti Action Plan etc.
microbes in production oF biogas
Biogas is a methane rich fuel gas produced by anaerobic breakdown or digestion of biomass with the help of methanogenic bacteria or methanogens Methanobacterium is a common methanogenicbacteria.
Biogas is made up of methane (50-70%), carbon dioxide (30-40%) with traces of nitrogen, hydrogen sulphide and hydrogen. 50% of the combustible energy present in the organic waste can be changed into methane gas. The energy released from biogas depends upon the proportion of methane present in it. The calorific value of biogas is 23-28 MJ/m3.
As the biogas production is an anaerobic process, it is carried out in an air tight, closed cylindrical concrete tank called a digester. The tank has a concrete inlet basin on one side for feeding fresh cattle dung. There is a concrete outlet on the outer side for removing the digested
sludge. The top of the tank serves as the gas tank. It has an outlet pipe for the biogas.
Biogas generation is a three-stage anaerobic digestion of animal and other organic wastes. The latter consist of lignin, cellulose, hemicellulose, lipids and proteins. Lignin cannot be broken down under anaerobic conditions.
Cellulose digestion is slower than that of other substances. In the first stage of anaerobic digestion (solubilisation), facultative anaerobic decomposer microbes bring about enzymatic breakdown of complex organic compounds into simpler and soluble compounds often called ‘monomers’. For this, the decomposer microbes secrete cellulases, proteases and lipases (cellulolytic, proteolytic and lipolytic enzymes).
In the second stage (acidogenesis), the simple soluble compounds of microbial digestion or monomers are acted upon by fermentation causing microbes. The latter change the monomers into organic acids. Organic acids, especially acetic acid, are acted upon by methanogenic bacteria in the third or final stage (methanogenesis). The methane bacteria convert organic acids as well as carbon dioxide into methane. The biogas thus formed is stored in tanks for supply.
The technology of biogas production was developed in India by collaboration of Indian Agriculture Research Institute (IARI) and
Khadi and Village Industries Commission (KVIC).
advantages of biogas
Using organic wastes first for biogas generation has following advantages over their direct use as fuel or fertiliser:
(i) It provides both energy and manure.
(ii) Biogas has wider applications than the direct burning of organic wastes.
(iii) The energy value of biogas is lower than that of organic matter but due to more efficient handling, the net energy output is roughly equal to the output in direct burning of organic wastes.
(iv) Minimises the chances of spread of faecal pathogens.
(v) The fertiliser value of the manure produced in biogas plants is similar to that of manure formed directly from organic wastes. (vi) Biogas use does not add to pollution.
microbes as biocontrol agents
The natural method of pest and pathogen control involving use of viruses, bacteria and other insects (which are their natural predators and pests) is called biocontrol or biological control.
For example, Lady bird beetle (beetle with red and black markings) feeds on aphids while dragonflies prey upon mosquitoes. Free living fungus Trichoderma exerts biocontrol over several plant pathogens.
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thuringiensis. These are available in sachets as dried spores. Spores of this bacterium contain insecticidal cry protein. These spores which are mixed with water and sprayed onto vulnerable plants such as Brassica and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed. Because of the development of methods of genetic engineering in the last decade or so, the scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests. Bt-cotton is one such example, which is being cultivated in some states of our country.
Baculoviruses are pathogens that attack insect pests and other arthropods. The majority of baculoviruses used as biological control
agents belong to the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.
some other biocontrol agents
Phytophthora palmivora
• - Controls growth of milkweed vine
Cercospora rodmanii
• - Controls growth of Eichhornia crassipes
Praying Mantis - Successful in combating scale insect
•
Beauveria bassiana
• - Successfully employed in controlling potato beetle Rodolia cardinalis
• - Controls cottony cushion scale (Icerya purchasi) Cyrtorhinus mundulus
• - Controls sugarcane leaf hopper.
microbes as bioFertilisers
Chemical fertilisers are being used in increasing amounts in order to increase output in high yielding varieties of crop plants.
However, chemical fertilisers cause pollution of water bodies as well as ground water, besides getting stored in crop plants. Therefore, environmentalists are pressing for switch over to organic farming. Organic farming is the raising of unpolluted crops through the use of manures, biofertilisers and biocontrol agents that provide optimum nutrients to crop plants, keeping pests and pathogens under control.
Biofertilisers are organisms which bring about nutrient enrichment of the soil by enhancing the availability of nutrients like nitrogen and phosphorus to the crops. Some of the important biofertilisers recommended for the use in agriculture are discussed ahead.
microphos biofertilisers
They release phosphate from bound and insoluble states, e.g., Bacillus polymyxa, Pseudomonas striata, Aspergillus species.
Free living nitrogen fixing bacteria
Free-living nitrogen fixing bacteria fix atmospheric nitrogen in the soil and make it available for the higher plants. The best example isAzotobacter. Apart from Azotobacter, some other genera of free living soil enhabiting bacteria such as Clostridium, Bacillus polymyxa, Beijerinckia, Klebsiella, Derxia and Rhodospirillum are also known to fix atmospheric nitrogen.
Inoculation of soil with these bacteria helps in increasing yield and saving of nitrogen fertilisers. For example, Azotobacter occurring in fields of cotton, maize, jowar and rice, not only increase yield but also saves nitrogen fertiliser to the tune of 10–25 kg/ha. Its inoculation is available under the trade name of azotobactrin.
symbiotic nitrogen fixing bacteria
They form a mutually beneficial association with the plants. The most important of the symbiotic nitrogen fixing bacteria is Rhizobium. The bacteria Rhizobium occurs freely in the soil but fails to fix nitrogen in the free state. It multiplies as soon as it gets to rhizosphere of leguminous plants, enters into their roots and forms specialised structures called root nodules. The bacteria fix atmospheric nitrogen only in the root nodules and that too when present in the bacteroid forms.
The genus Rhizobium includes many species and each species further includes many strains. It has been observed that a specific strain of Rhizobium sp. gets symbiotically associated with specific species of leguminous plant, e.g., Rhizobium leguminosarum (in pea), R. meliloti (in alfalfa), R. trifolii (in clover), R. phaseoli (in beans), R. lupini (in lupines) and R. japonicum (in soybeans), etc. Therefore, it is important to apply specific strain of Rhizobium to a particular leguminous crop in order to get maximum advantage.Frankia, a nitrogen fixing mycelial bacterium (actinomycete), is associated symbiotically with the root nodules of several nonlegume plants like Casuarina, Alnus (alder) Myrica, Rubus, etc.
loose association of nitrogen fixing bacteria
Certain nitrogen fixing bacteria like Azospirillum live around the roots of higher plants without developing any intimate relationship. It is often called rhizosphere association. The bacteria obtain some plant exudate and use the same as part of their food requirement. The bacteria fix nitrogen and exude a part of the fixed nitrogen for use by the plant. The phenomenon is termed as
associative mutualism or associative symbiosis.
Free living nitrogen fixing cyanobacteria
A number of free living cyanobacteria or blue-green algae have the property of nitrogen fixation, e.g., Anabaena, Nostoc, Aulosira, Totypothrix, Cylindrospermum, Stigonema. Aulosira fertilissima is considered to be the most active nitrogen fixer of rice fields in India (Aiyer et al, 1972). Cylindrospermum licheniforme grows in sugarcane and maize fields. Cyanobacteria are extremely low cost biofertilisers.
symbiotic nitrogen fixing cyanobacteria
Nitrogen fixing cyanobacteria (blue-green algae) form symbiotic association with several plants, e.g., cycad roots, lichens, liverworts, Azolla (fern). Azolla-Anabaena association is of great importance to agriculture. Anabaena azollae resides in the leaf cavities of the fern Azolla where it fixes nitrogen.
mycorrhiza
It is a mutually beneficial or symbiotic association of a fungus with the root of a higher plant. The most common fungal partners of mycorrhiza are Glomus species. Depending upon the residence of the fungus, mycorrhizae are of two types– ectomycorrhiza and endomycorrhiza.
In ectomycorrhiza the fungal mycelium completely encloses the feeder rootlets forming sheath or mantle. The hyphae penetrate the intercellular spaces of the root cortex to form a network, called the ‘Hartig net’. The mantle of fungal hyphae increases the absorptive surface of roots and hence serve better intake of nutrients such as nitrogen, phosphorus, calcium and potassium from the surrounding soil. Ectomycorrhizae are known to occur in several genera such as Pinus, Quercus, Betula, Alnus, Salix, Populus etc. In endomycorrhiza fungus does not form an external sheath of mantle. The fungus mostly lives in the intercellular spaces as well as intracellularly in the cortical cells of roots. Only a small portion of fungus lives outside the root. Such type of mycorrhizal association occurs in the roots of grasses, cereals, legumes, rubber, tea, tobacco, soybean, citrus and in many orchids (Neottia, Vanilla, Galeola, Epipogon, etc.).
One of the important type of endomycorrhizae is vesicular-arbuscular mycorrhizae (VAM). In this association, the fungal mycelium forms some special kinds of organs, called vesicles and arbuscules, within the root cortical cells. They serve as the
food storage organs of the fungus. Endomycorrhizae stimulate the absorption of phosphorus, zinc, copper, sulphur, potassium
and various other elements by roots. They secrete antimicrobial substances to protect the plants from pathogen attack.
importance of biofertilisers
(i) They increase the yield of plants by 15–35%. (ii) Biofertilisers are effective even under semi-arid conditions. (iii) Farmers can prepare the inoculum themselves. (iv) They improve soil texture.
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New MCQs
1. The inoculum is added to the fresh milk in order to convert milk into curd, the term ‘inoculum’ here refers to
(a) a starter rich in vitamin B12
(b) a starter rich in proteins
(c) a starter containing millions of LAB (d) an aerobic digester.
2. Living organisms used to enrich the nutrient quality of the soil are called as
(a) biocontrol agents (b) biofertilisers (c) synthetic fertilisers (d) natural fertilisers.
3. Which of the following beneficial bacteria is also present in the rumen of cattle?
(a) Azotobacter (b) Rhizobium (c) Methanobacterium (d) Azospirillum
4. Which of the following is the biocontrol agent for cottony cushion scale (Icerya purchasi)?
(a) Cyrtorhinus mundulus (b) Rodolia cardinalis (c) Beauveria bassiana (d) Phytophthora palmivora
5. During the primary treatment of sewage, solid particles that settle down are called
(a) flocs (b) primary sludge (c) activated sludge (d) anaerobic sludge.
6. Members of which of the following microbial groups do not have much beneficial value?
(a) Fungi (b) Prions
(c) Bacteria (d) Protozoa 7. Which of the following statements is incorrect?
(a) Word antibiotic is a misnomer. Anti is a Greek word that means ‘against’, and bio means ‘life’, together they mean ‘against life’ (in the context of disease causing organisms); whereas with reference to human beings, they are ‘pro life’ and not against.
(b) Flocs are masses of bacteria with interwoven fungal filaments which form mesh like structures.
(c) Components of biogas are methane (50 – 70%), carbon dioxide (30 – 40%) and traces of hydrogen, nitrogen and H2S.
(d) None of these
8. A cholesterol lowering agent is obtained from (a) Aspergillus niger (b) Trichoderma polysporum (c) Pencillium notatum (d) Monascus purpureus
9. _____ is the first step of sewage treatment. (a) Precipitation (b) Chlorination (c) Sedimentation (d) Aeration
10. Which of the following statements is correct with regard to biocontrol agents?
(a) Ladybird beetles and dragonflies are used to get rid of aphids and mosquitoes.
(b) Bacillus thuringiensis bacteria are used to control butterfly caterpillars.
(c) Trichoderma species are used to control several plant pathogens.
(d) All of these
11. Fumagillin is a (i) antibiotic obtained from (ii) and is effective against (iii) .
(a) (i) broad spectrum (ii) Aspergillus fumigatus (iii) Salmonella
(b) (i) specific
(ii) Penicillium griseofulvum (iii) spirochaetes
(c) (i) broad spectrum (ii) Gliocladium virens (iii) Shigella
(d) (i) Specific
(ii) Streptomyces venezuelae (iii) Pseudomonas
12. Which of the following are the characteristics of a good antibiotic?
(a) Harmless to host with no side effect (b) Ability to destroy all strains of pathogen (c) Quick action
(d) All of these
13. Rancidity of butter is due to
(a) gluconic acid (b) citric acid (c) butyric acid (d) lactic acid.
14. Leavening of kneaded flour mixed with yeast is caused by enzyme
(a) amylase (b) maltase
(c) zymase (d) all of these.
15. Toddy is a traditional drink of some parts of South India which is obtained by
(a) unopened spadices of coconut (b) soyabean and wheat
(c) tender bamboo shoots (d) rice and black gram.
Exam Section
1. Viruses of the genus Nucleopolyhedrovirus are employed as (a) gobar gas producers
(b) biological control agents (c) anaerobic sludge digesters (d) antibiotics
(e) atmospheric nitrogen fixing agents.
(Kerala PMT 2014)
2. Select the correct pair of microorganism and the product obtained from it.
(a) Monascus purpureus - produces large holes in Swiss cheese.
(b) Saccharomyces cerevisiae - used for making wine and beer after distillation.
(c) Streptococcus - produces streptokinase which is used to remove clots.
(d) Aspergillus niger - produces citric acid and butyric acid.
(AIIMS 2014)
3. Wine and beer are produced directly by fermentation whereas brandy and whisky require both fermentation and distillation. This is because
(a) fermentation is inhibited at an alcohol level of 10-18% (b) distillation prolongs storage
(c) distillation improves quality (d) distillation purifies the beverage.
(AIIMS 2014)
4. Yeast is used for commercial production of
(a) methanol (b) ethanol
(c) butanol (d) citric acid. (AMU 2014)
5. Statin, a blood-cholesterol lowering agent, is commercially obtained from
(a) Trichoderma polysporum (b) Acetobacter aceti (c) Clostridium butylicum (d) Monascus purpureus.
(AMU 2014)
6. ‘Roquefort cheese’ is ripened by using a (a) bacterium (b) type of yeast (c) cyanobacteria (d) fungus.
(Karnataka CET 2014)
7. Match the microbial products listed under Column I with the related microbes given under Column II. Choose the appropriate option from the given choices.
Column I Column II
A. Citric acid p. Methanobacterium B. Cyclosporin A q. Monascus purpureus C. Statin r. Aspergillus niger D. Gobar gas s. Trichoderma polysporum
t. Clostridium butylicum
(a) A-q; B-s; C-t; D-r (b) A-r; B-s; C-q; D-p (c) A-r; B-s; C-q; D-t (d) A-t; B-q; C-s; D-r
(Karnataka CET 2014)
8. Microorganism used for commercial production of acetic acid is
(a) Saccharomyces cerevisiae (b) Aspergillus niger
(c) Acetobacter
(d) Clostridium butylicum.
(J & K 2014)
9. Which of the following microbes is correctly matched with its function?
(a) Aspergillus niger – Production of lactic acid (b) Trichoderma – Lowers blood cholesterol
polysporum
(c) Saccharomyces – Production of citric acid cerevisiae
(d) Methanogenic – Gobar gas formation bacteria
(AIIMS 2014)
10. Microbe used for biocontrol of pest butterfly caterpillars is (a) Saccharomyces cerevisiae
(b) Bacillus thuringiensis (c) Streptococcus sp.
(d) Trichoderma sp. (NEET - Karnataka 2013) 11. Which one of the following microbes forms symbiotic
association with plants and helps them in their nutrition? (a) Azotobacter (b) Aspergillus
(c) Glomus (d) Trichoderma
(AIPMT Prelims 2012)
12. A nitrogen-fixing microbe associated with Azolla in rice fields is
(a) Spirulina (b) Anabaena (c) Frankia (d) Tolypothrix.
(AIPMT Prelims 2012)
13. Which one of the following is an example of carrying out biological control of pests/diseases using microbes? (a) Trichoderma sp. against certain plant pathogens. (b) Nucleopolyhedrovirus against white rust in Brassica. (c) Bt-cotton to increase cotton yield.
(d) Lady bird beetle against aphids in mustard.
(AIPMT Prelims 2012)
14. Match the items in Column I with those in Column II and select the correct answer from the codes given below.
Column I Column II
P. Blue green algae as (i) Ectomycorrhiza biofertilisers
Q. Fungi as biofertilisers (ii) Thiobacillus sp. R. Free living nitrogen (iii) Anabaena sp.
fixing bacteria
S. Phosphate solubilising (iv) Clostridium sp. bacteria
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(a) P-(iii), Q-(i), R-(iv), S-(ii) (b) P-(iii), Q-(i), R-(ii), S-(iv) (c) P-(iii), Q-(iv), R-(i), S-(ii) (d) P-(iv), Q-(ii), R-(i), S-(ii)
(WB JEE 2012)
15. Free living bacteria that can fix N2 from soil is (a) Clostridium (b) Azotobacter (c) Beijerinckia (d) all of these.
(Odisha 2012)
16. Due to which of the following organisms, yield of rice is increased?
(a) Sesbania (b) Bacillus popilliae (c) Anabaena (d) Bacillus subtilis
(CBSE 1999; BHU 2012)
17. Which one of the following is not a biofertiliser?
(a) Agrobacterium (b) Rhizobium
(c) Nostoc (d) Mycorrhiza
(AIPMT Prelims 2011)
18. An organism used as a biofertiliser for raising soyabean crop is
(a) Azotobacter (b) Azospirillum (c) Rhizobium (d) Nostoc.
(AIPMT Prelims 2011)
19. Which one of the following is not used in organic farming?
(a) Glomus (b) Earthworm
(c) Oscillatoria (d) Snail.
(AIPMT Prelims 2011)
20. Consider the following statements (A–D) about organic farming.
(A) Utilises genetically modified crops like Bt cotton. (B) Uses only naturally produced inputs like compost. (C) Does not use pesticides and urea.
(D) Produces vegetables rich in vitamins and minerals. Which of the above statements are correct?
(a) B, C and D (b) C and D only (c) B and C only (d) A and B only
(AIPMT Mains 2011)
21. Select the correct statement.
(a) Acetobacter aceti produces citric acid.
(b) Saccharomyces cerevisiae is used as clot buster. (c) Penicillium notatum restricts the growth of
Staphylococci.
(d) Methanogens are found in aerobic conditions.
(AIIMS 2011)
22. Biogas produced by fermentation of manure, sewage, cattle dung, etc., predominantly comprises
(a) methane, nitrogen and hydrogen (b) methane and carbon dioxide (c) methane and carbon monoxide
(d) methane and nitric oxide. (DUMET 2011)
23. Trichoderma species are potentially useful as (a) biopesticides
(b) biofertilisers (c) methanogens
(d) vectors for genetic engineering. (DUMET 2011)
24. Biogas production is carried out by (a) thermoacidophiles (b) methanogens
(c) halophiles (d) ruminants. (AFMC 2011)
25. Which one of the following is a bacterial biofertiliser? (a) Anabaena (b) Nostoc
(c) Rhizobium (d) Oscillatoria (J & K 2011)
26. Which of the following is not used as a biopesticide? (a) Trichoderma harzianum
(b) Nuclepolyhedrovirus (c) Xanthomonas campestris
(d) Bacillus thuringiensis (CBSE 2009)
27. Which is not a biofertiliser? (a) Rhizobium leguminosarum (b) Anabaena
(c) Bacillus thuringiensis
(d) Nostoc (DPMT 2008)
28. An insecticide extracted from the leaves of neem is (a) aldicarb (b) malathion
(c) rotenone (d) azadirachtin.
(UP-CPMT 2008)
29. Most potential organism for the production of insecticide is (a) Xanthomonas oryzae (b) Bacillus thuringiensis (c) Erannis tiliaria (d) Heliothis zea (Odisha 2007)
30. Which of the following is free living aerobic and non-photosynthetic nitrogen fixing bacterium ?
(a) Azotobacter (b) Rhizobium (c) Anabaena (d) Clostridium
(J & K 2004, 2005)
Assertion & Reason
The following questions consist of two statements each : assertion (A) and reason (R). To answer these questions, mark the correct alternative as directed below :
(a) If both A and R are true and R is the correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) If A is true but R is false. (d) If both A and R are false.
1. Assertion : Curd is more nutritious than milk as it contains
a number of organic acids and vitamin B12.
Reason : LAB present in curd check growth of disease causing microbes in stomach.
2. Assertion : Pathogens often develop resistance to existing
Reason : The resistance is generally produced due to extrachromosomal genes present in plasmids.
3. Assertion : Citric acid was the first organic acid to be
produced from the microbial fermentation in starchy and sugary medium.
Reason : Rancidity of butter is due to formation of citric acid.
4. Assertion : Rennet is an extract from the stomach of calf
that contains enzyme rennin.
Reason : Rennet is added in detergents for removing oily stains from laundry.
5. Assertion : A high Biochemical Oxygen Demand (BOD)
indicates the presence of large number of microorganisms in a water body which suggests a high level of pollution.
Reason : BOD is the amout of oxygen taken up by microorganisms that decompose organic waste matter in water.
6. Assertion : The excreta of cattle is used for the generation
of biogas, commonly called gobar gas.
Reason : Methanogens, which grow aerobically on cellulose material help in the production of gobar gas.
7. Assertion : Nucleopolyhedrovirus has been shown to have
no negative impacts on plants, mammals, birds, fish or even on non-target insects.
Reason : Nucleopolyhedrovirus is excellent genus for species
specific narrow spectrum insecticidal applications.
Short Answer Type Questions
1. Milk starts to coagulate when lactic acid bacteria (LAB) is added to warm milk as a starter. Mention any other two benefits LAB provides.
2. What does “leg” in leghaemoglobin refer to? Why is this pigment called oxygen-scavenger?
3. Explain various methods used for carrying out fermentation process.
4. Describe the steps involved in the production of an antibiotic.
5. (i) How is activated sludge produced during sewage treatment?
(ii) Explain how this sludge is used in biogas production. 6. Compare biocontrol agents and biofertilisers.
7. Explain the scientific reason for growing Azolla pinnata in the
rice field. .
Answer Key
New MCQs 1. (c) 2. (b) 3. (c) 4. (b) 5. (b) 6. (b) 7. (d) 8. (d) 9. (c) 10. (d) 11. (a) 12. (d) 13. (c) 14. (d) 15. (a) Exam Section 1. (b) 2. (c) 3. (d) 4. (b) 5. (d) 6. (d) 7. (b) 8. (c) 9. (d) 10. (b) 11. (c) 12. (b) 13. (a) 14. (a) 15. (d) 16. (c) 17. (a) 18. (c) 19. (d) 20. (c) 21. (c) 22. (b) 23. (a) 24. (b) 25. (c) 26. (c) 27. (c) 28. (d) 29. (b) 30. (a)Assertion & Reason
1. (b) 2. (b) 3. (d) 4. (c) 5. (a)
6. (c) 7. (a)
Short Answer Type Questions
1. Two benefits provided by LAB are :
(i) It increases nutritional quality of curd by increasing vitamin B12 content.
(ii) It checks the growth of disease-causing organisms in the gut.
2. The ‘leg’ in leghaemoglobin refers to leguminous plants. The leghaemoglobin is referred to as oxygen scavanger because it combines rapidly with O2 to avoid any inhibitory effect of oxygen on the enzyme nitrogenase.
3. Fermentation can be done using three different methods: (i) Batch culture : In the batch culture, the conditions are set
up and not changed from outside once the fermentation starts; for example, no more nutrients are added. This is why the process is described as a closed system. The process is stopped once sufficient product has been formed. The contents of the fermenter are then removed, the product isolated, the microorganism discarded and the fermenter is cleaned and set up for a fresh batch. (ii) Continuous culture : Continuous culture involves
continuous long-term operation over many weeks, during which nutrient medium is added as fast as it is used, and the overflow is harvested. Although this is closer to the situation in natural environments, such as the gut, continuous culture has found only limited application. However, it is used for the production of single cell protein where a large biomass of cells is required.
(iii) Fed-batch culture : This is a compromise between the two systems. With fed-batch culture more control of the process is involved than with batch culture. The period of growth is extended by adding nutrients at low concentrations during the fermentation, and not adding all the nutrients at the beginning. One advantage of this is that the rate of growth can be regulated to keep pace with the rate at which oxygen can be supplied. The process is commonly used to produce yeast cells for the baking industry.
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4. Various steps involved in the production of an antibiotic are as follows:
5. (i) A large number of aerobic heterotrophic microbes grow in the aeration tank. They include bacteria, some filamentous fungi, yeast and protozoans. These aerobes grow in “flocs” and consume a major part of organic matter so that the BOD of sewage is reduced. Now the effluent is passed through a sedimentation tank where microbial flocs are allowed to settle down. The settled materials is called ‘activated sludge’.
(ii) A small part of the activated sludge is pumped back into
the aeration tank to serve as the inoculum. The remaining major part of the activated sludge is pumped into large tanks called anaerobic sludge digesters. The aerobic microbes in the sludge get killed. The anaerobic bacteria digest the organic
mass including dead bacteria and fungi in the sludge and produce mixture of gases like methane, hydrogen sulphide and CO2 which constitute biogas. The left out sludge is used
as manure.
6. The natural method of pest and pathogen control involving use of viruses, bacteria and other insects (which are their natural predators and pests) is called biocontrol or biological control. For example, Lady bird beetle (beetle with red and black markings) feeds on aphids while dragonflies prey upon mosquitoes. Free living fungus Trichoderma exerts biocontrol over several plant pathogens. An example of microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis. Biofertilisers are the microorganisms such as bacteria, cyanobacteria, fungi etc., which bring about soil nutrient enrichment, maximise the ecological benefits and minimise the environmental hazards.
7. Azolla pinnata is a free floating fresh water fern which multiplies rapidly, doubling every 5–7 days. The fern can coexist with rice plants because it does not interfere with their growth. A symbiotic blue green algae, Anabaena azollae resides in the leaf cavities of the fern. It fixes nitrogen. A part of the fixed nitrogen is excreted in the cavities and becomes available to the fern. The decaying fern plants release the same for utilisation of the rice plants. When field is dried at the time of harvesting, the fern functions as the green manure, decomposing and enriching the field for the next crop.
Unscramble the given words using the references given below.
Scrambled letters Clues Words
1. POIETEP Antigenic determinant. ...
2. VSAINONI A stage of ecological succession. ... 3. IRPOAMRACOPIOGTN Helps in rapid multiplication of plants. ... 4. GNYOLSYECO An ecological study at community level. ... 5. BVNILFIORA Also called yellow enzyme and its deficiency
causes cheilosis. ...
6. TCIFOIRNBITOIAFO Plant breeding for improved food quality. ...
7. YHRONTAKORE Male birth. ...
8. PECLTSOUAL Plant cell organelle which stores substances
like starch, fat and proteins. ...
9. INCTNLAOIC Peptide hormone that acts opposite to
parathyroid hormone in Ca2+ metabolism. ...
10. ESRKAPTSIOTEN Helps in clearing blood clots inside the
blood vessels. ...
M E
U N S C R A M B L E
Readers can send their answer with complete address by 10th of every month to win exciting prizes.
If you have a bone marrow transplant, your blood can have the donor’s DNA and your salival and hair DNA will be your own. It has caused people to be wrongly arrested based on DNA evidence.
If you could type 60 words per minute, eight hours a day, it would take approximately 50 years to type the human genome.
If you were to lay out all the arteries, capillaries and veins in one adult, end-to-end, they would stretch about 60,000 miles (100,000 kilometers). Even more interesting is that, the capillaries, which are the smallest of the blood vessels, make up about 80 percent of this length. By comparison, the circumference of the Earth is about 25,000 miles (40,000 km). That means a person’s blood
vessels could wrap around the planet approximately 2.5 times.
Across the animal kingdom, heart rate is inversely related to body size. In general, the bigger the animal, the slower is its resting heart rate. A blue whale’s heart is about the size of a compact car, and beats only five times per minute. A shrew, on the other
hand, has a heart rate of about 1,000 beats per minute.
The average strawberry has 200 seeds. It’s the only fruit that bears its seeds on the outside.
Honey bee is the only insect that produces food eaten by man. Honey is the only insect created food with therapeutic, medicinal, nutritional and cosmetic
value.
The honey bee’s wings stroke incredibly fast, about 200 beats per second, thus making their famous, distinctive buzz. A honey bee can fly for upto six miles, and as fast as 15 miles per hour.
While awake, your brain generates between 10 and 23 watts of power or enough energy to power a light bulb.
Much like fingerprints, everyone also has a unique tongue print. The acid in your stomach is so powerful that it can dissolve razor blades. It is impossible to tickle yourself. Actually two brain regions are involved in
the processing how tickling feels. The somatosensory cortex processes touch and the anterior cingulate cortex processes pleasant information. Both these regions are less active during self-tickling as compared to tickling
performed by someone else.
The earth has more than 80,000 species of edible plants.
Pomology is the branch of horticulture that is concerned with study and cultivation of fruits.
The world’s most popular fruit is the tomato. Tomatoes have more genes than humans.
Fallopian tube is no wider than the head of a pin.
The female human body is capable of giving birth to 35 children in one lifetime.
The human reproductive system contains the largest and smallest cells. Sperm cell is smallest (5 mm × 3 mm in size) and female’s ovum is
the largest human cell (about 120 mm is diameter).
There is a positive correlation between vitamin D and testosterone levels in men. The more sunlight exposure a man gets the more likely it is that he has elevated testosterone levels.
Cuddling helps to heal physical wounds faster due to the release of oxytocin, which is proven to reduce swelling.
Laughter is usually the best natural medicine for stress. It lowers levels of cortisol, adrenaline, etc., which are stress aggravating hormones; and it releases feel-good hormones, such as endorphins.
While sitting at your desk, make clockwise circles with your right foot, while doing this, draw the number “6” in the air with your right hand. Your foot will change the direction.
Intelligent people have more zinc and copper in their hair. The surface area of human lung is equal to tennis court.
Human nose can detect 50,000 different scents.
The HIV-genome, which is about 10,000 nucleotides long, can exist as 106020 different sequences. To compare there are 1011 stars in the Milkyway galaxy and 1080 protons in the universe.
Coral reefs are the most diversified of all ecosystems on Earth.
Madagascar is an example of biodiversity hotspot because almost all of its living organisms cannot survive anywhere
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1. In the first step of monohybrid cross experiment, Mendel selected pea plants which were
(a) pure tall as male and pure dwarf as female (b) pure tall as female and pure dwarf as male (c) heterozygous tall as male and pure dwarf as female (d) heterozygous tall as female and pure dwarf as male. 2. In Griffith’s experiment, the conversion of R-type to S-type of
Diplococcus pneumoniae when mixed with heat killed S-type is called
(a) mutation (b) transduction (c) transfection (d) transformation. 3. Semi-dwarf rice variety IR-8 was developed in
(a) Taiwan (b) Philippines
(c) India (d) China.
4. Which one of the following is a non-endospermic seed? (a) Sunflower (b) Coconut
(c) Groundnut (d) Wheat
5. Which one of the following is not a mycoherbicide? (a) Phytophthora palmivora
(b) Xanthomonas sp. (c) Alternaria crassa (d) Fusarium sp.
6. During anaerobic respiration the conversion of pyruvate into acetaldehyde, along with co-enzyme TPP, the cofactor required is
(a) Mg++ (b) Mn++
(c) Fe++ (d) Zn++.
7. An international treaty known as Montreal Protocol was signed to control emission of
(a) uV rays (b) ozone
(c) CFC (d) oxygen.
8. Chloroplasts in higher plants are ________ shaped.
(a) kidney (b) lens
(c) bean (d) dome
9. Pollen grain develops from _________ of anther. (a) epidermis
(b) endothecium (c) tapetum
(d) sporogenous tissue
10. In processing of eukaryotic hnRNA, during protein synthesis tailing involves __________ of RNA.
(a) addition of adenylate residues at 3’ end
(b) addition of methyl guanosine triphosphate at 3’ end (c) addition of methyl guanosine triphosphate at 5’ end (d) removal of introns
11. In a cross between red kernelled and white kernelled varieties of wheat showing polygenic inheritance the phenotypic ratio in F2 generation will be
(a) 1 : 6 : 15 : 20 : 15 : 6 : 1 (b) 1 : 4 : 6 : 4 : 1
(c) 1 : 2 : 1 (d) 2 : 1.
12. In angiosperms during development of embryo the suspensor cells develop from
(a) oospore (b) integument
(c) endosperm (d) cotyledon.
13. Manganese, calcium and chloride ions present in PSII play an important role in
(a) absorption of light (b) CO2 assimilation (c) photolysis of water (d) ATP synthesis.
14. Which process does the following equation represent ? C6H12O6 + 2NAD + 2 ADP + 2 Pi → 2 CH3 – CO – COOH
+ 2 NADH2 + 2 ATP (a) Complete glycolysis
(b) Complete aerobic respiration (c) Complete anaerobic respiration (d) Complete fermentation
15. The cloning vector M13 has genetic material
(a) ssRNA (b) dsRNA
(c) ssDNA (d) dsDNA.
MH-CET
16. Earthworm is a
(a) herbivore (b) secondary consumer (c) tertiary consumer (d) detritivore.
17. To induce formation of organs in a callus it is necessary to provide
(a) growth hormones (b) water
(c) soil (d) antibiotics.
18. Anemophily is not observed in
(a) maize (b) jowar
(c) sugar cane (d) Salvia.
19. In an ecosystem, the biotic components herbivores are (a) photosynthetic (b) chemosynthetic (c) macroconsumers (d) microconsumers.
20. The visible portion of light spectrum useful in photosynthesis is referred to as
(a) RFlP (b) PAR
(c) VAM (d) VNTR.
21. The microbe Pseudomonas denitrificans produces vitamin (a) K (b) D (c) B2 (d) B12.
22. If there are 1280 microspores in a tetralocular anther, how many microspore mother cells will be there in its each pollen chamber ?
(a) 80 (b) 160
(c) 240 (d) 1280
23. Which one of the following plants does not help in vegetative propagation by leaves ?
(a) Begonia (b) Kalanchoe
(c) Bryophyllum (d) Oxalis
24. Given below are some reactions and the enzymes involved. Identify the correct pairs.
Column I Column II
1. Fructose 1, 6 diphosphate A. Enolase → 3PGAl + DHAP
2. Citrate → Cis-aconitate B. Thiokinase 3. Succinyl Co A → Succinate C. Aconitase
4. 2 PGA → PEP D. Aldolase
(a) 1-D, 2-C, 3-B, 4-A (b) 1-A, 2-B, 3-C, 4-D (c) 1-B, 2-A, 3-D, 4-C (d) 1-C, 2-D, 3-A, 4-B 25. Human skin colour is an example of
(a) intragenic interaction (b) interallelic interaction (c) quantitative inheritance (d) pleiotropy.
26. During DNA replication, the addition of nucleotides on the lagging strand occurs
(a) towards the replicating fork (b) at a faster rate than leading strand (c) continuously
(d) discontinuously.
27. The technique of producing large number of genetically similar plants within short time by tissue culture is called
(a) organogenesis (b) somatic hybridisation (c) micropropagation (d) protoplast culture.
28. How many sense codons code for 20 known essential amino acids ?
(a) 61 (b) 62
(c) 63 (d) 64
29. Which one of the following is not a natural method of vegetative propagation ?
(a) Runner (b) Foliar buds (c) Stem tuber (d) Grafting 30. Transposons are sequences of
(a) DNA (b) mRNA
(c) rRNA (d) tRNA.
31. A 340 Å long segment of DNA molecule has 20 thymine nitrogenous bases, what will be the number of guanine nitrogen bases in the same segment ?
(a) 10 (b) 40
(c) 80 (d) 160
32. The final electron acceptor during ETS in respiration is (a) hydrogen (b) oxygen
(c) FMN (d) ubiquinone.
33. The time taken from the fixation of CO2 to the formation of one glucose molecule is about _________ seconds.
(a) 20 (b) 40
(c) 60 (d) 90
34. The secondary metabolite obtained from Catharanthus roseus is
(a) vincristine (b) anthocyanin (c) menthol (d) nicotine.
35. large stout, nocturnal flowers producing copious nectar and emitting fermenting fruity odour, are the adaptations for
(a) entomophily (b) ornithophily (c) chiropterophily (d) anemophily.
36. During biogas production acetic acid is transformed into the final product by the enzymes of
(a) Clostridium (b) Pseudomonas (c) Penicillium (d) Methanobacillus.
37. The gymnospermic endosperm differs from an angiospermic endosperm because in gymnosperms it is
(a) haploid and developed from female gametophyte (b) diploid and developed from female gametophyte (c) triploid and developed after fertilisation (d) triploid and developed before fertilisation.
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38. What is not true about emasculation of a flower while performing an artificial cross ?
(a) It is removal of anthers from flower. (b) It is done before anthesis.
(c) It is to avoid self pollinaton.
(d) It is done in flowers of plants selected as male parent. 39. Pusa Shubhra is a variety of
(a) cauliflower (b) chilli
(c) wheat (d) cabbage.
40. Which of the following is correct pair of pyrimidine bases?
(a) Adenine and thymine (b) Adenine and guanine (c) Thymine and cytosine (d) Guanine and cytosine
41. In the nomenclature of enzyme restriction endonuclease the Roman numeral indicates
(a) number of times it is used (b) the order of discovery from source (c) number of cuts on DNA
(d) number of recombinants formed.
42. Environmental biotic factor that helps in pollination is
(a) air (b) water
(c) wind (d) insect.
43. How many types of gamete will be produced by an individual having genotype AaBbcc ?
(a) Four (b) Three
(c) Two (d) One
44. Self pollination which involves two different flowers of the same plant, is called
(a) autogamy (b) geitonogamy (c) xenogamy (d) hybridisation. 45. The initial step in preparation of beer is
(a) malting (b) carboxylation (c) clarification (d) distillation.
46. A desirable change in genotype of an organism is obtained by
(a) DNA replication (b) protein synthesis (c) rDNA technology (d) mRNA formation.
47. Considering mode of asexual reproduction, match the Column I with Column II and select the correct option.
Column I Column II
A. yeast i. Fragmentation
B. Penicillium ii. Zoospores
C. Filamentous algae iii. Budding D. Chlamydomonas iv. Conidia (a) A-iii, B-iv, C-i, D-ii (b) A-ii, B-iii, C-i, D-iv (c) A-iv, B-iii, C-ii, D-i (d) A-iii, B-ii, C-i, D-iv
48. How much of the energy released during aerobic respiration is approximately conserved in the form of ATP ?
(a) 20% (b) 40%
(c) 60% (d) 100%
49. The deflection of pitch angle between two successive steps (rungs) of DNA is
(a) 72° (b) 54°
(c) 36° (d) 18°.
50. Which one of the following is a CAM plant ?
(a) Maize (b) Kalanchoe
(c) Sugar cane (d) Jowar
51. One of the following cells secretes a hormone (a) cells of leydig
(b) cells of Sertoli (c) primary spermatocyte (d) secondary spermatocyte.
52. Find the odd one out, with respect to X-linkage. (a) Haemophilia (b) Myopia
(c) Nephritis (d) Night blindness 53. The first fossil of Australopithecus was discovered in
(a) Olduvai Gorge, Tanzania (b) Fayum deposits of Egypt (c) Siwalik hills in India (d) Tuang in South Africa.
54. Which of the following options are correct ?
1. Heroin – Stimulant
2. Marijuana – Cardiovascular
3. Cocaine – Hallucinations
4. Morphine – Sedative
(a) 1, 2 and 3 (b) 1, 3 and 4 (c) 2, 3 and 4 (d) 1, 2, and 4
55. Serotonin and melatonin are hormones, secreted by (a) pancreas (b) pineal body
(c) pituitary gland (d) thymus.
56. The characters such as pointed elongated snout, and strong and stout forelimbs, well developed claws are observed in __________ adaptation.
(a) arboreal (b) aerial (c) cursorial (d) fossorial
57. Deposition of ________ in the joints causes gout.
(a) urea (b) uric acid
(c) guanine (d) ammonia
58. The glycoprotein, fertilizin is secreted by
(a) ovum (b) ovary
