Viruses & Bacteria

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(1)Viruses & Bacteria Characteristics, Diseases, and Human Immune Response.

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(3) Introduction to Bacteria • Prokaryotes – Single-celled organisms (Unicellular) – No membrane-bound nucleus – Have a cell membrane – Smaller than smallest Eukaryotes.

(4) Kingdom Monera • Archaea – Means ancient – More closely related to eukaryotes – 3 groups • Methanogens • Halophiles • Thermoacidophiles.

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(6) Kingdom Monera • Eubacteria – Most known prokaryotes are bacteria – They come in three basic shapes • Bacilli (Rod-shaped) • Cocci (Sphere-shaped) – Chains (streptococci) – Clusters (staphylococcus). • Spirilla (Spiral-shaped).



(9) Laboratory Techniques • Gram Staining – The technique involves staining bacteria with a purple dye (Crystal violet) and iodine then the sample is rinsed with alcohol – The sample is then restained with pink dye (Safarinin). *Know the steps.

(10) Gram Staining • It is based on the structure of their cell walls as shown through a lab technique called the gram staining technique.

(11) Gram Staining • Gram-negative bacteria – Have cell walls that are complex and have relatively small amounts of peptidoglycan – They will appear reddish-pink under a microscope. Examples: E. coli, Pertussis, and Salmonella typhi.

(12) Gram Staining • Gram-positive bacteria are simpler and have more peptidoglycan so their cell walls appear purple under a microscope. Streptococcus, Staphylococcus, and Clostridium tetanii are Examples.

(13) Bacterial Structure.

(14) Bacterial Structure • Capsule & Slime Layer – Protect the cell and assist in attaching the cell to other surfaces.

(15) Bacterial Structure • Endospore – Protects the cell against harsh environmental conditions, such as heat or drought.

(16) Bacterial Structure • Pili – Assists the cell in attaching to other surfaces, which is important for genetic recombination (pili means hair).

(17) Environmental & Industrial Microbiology • Agriculture – Pesticide • Bacillus thuringiensis (Bt) – Protein that acts as a toxin to certain plant seeds. – Nitrogen fixation • Some bacteria are used to convert atmospheric nitrogen into a usable form of nitrogen for plants; thus, cycling nitrogen in the biosphere.

(18) Bioremediation • Definition – Uses bacteria to break down pollutants. • Environmental Clean-up – Oil spills and mine wastes.

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(22) Sewage Treatment • Bacteria break down organic matter in dead plant and animal waste • They turn sewage into simpler organic compounds (Decomposers).

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(25) Food • • • •. Yogurt Pickles Cheese Coffee.

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(27) Viruses • Viruses are nonliving particles made up of nucleic acids and a protein coat or a lipid protein coat.

(28) Viruses • Viruses are not alive. They lack some key characteristics of living organisms – No Cytoplasm – No Organelles – Cannot carry out cellular functions (such as homeostasis & metabolism) – They have DNA or RNA, however they can only reproduce inside a host cell.

(29) Viral Structure • Capsid – A protein coat that surrounds a virus. • Envelope – A bilipid membrane that surrounds the capsid.

(30) Viral Replication • Outside of a host cell, viruses have no control of their movements • They are spread by air, water, food, or bodily fluids.

(31) Lytic Cycle • During the lytic cycle, a virus invades a host cell, produces new viruses, and ruptures the host cell releasing the newly formed viruses • Virulent is the word attributed to viruses that replicate only through the lytic cycle.

(32) Lysogenic Cycle • The lysogenic cycle allows viruses to hide in their host cell for days, months, or years • Temperate virus is the word associated with viruses that replicate using the lysogenic cycle.

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(34) Bacterial & Viral Diseases • Pathology – The study of diseases. • Toxins – Disease causing poisons produced by bacteria. • Vector – Is an intermediate host that transfers a pathogen or a parasite to another organism.

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(36) Would you like some E coli with your fries?.

(37) Koch’s Postulates 1.. the microorganism or other pathogen must be present in all cases of the disease. 2.. the pathogen can be isolated from the diseased host and grown in pure culture. 3.. the pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal. 4.. the pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen.

(38) No pathogen. Healthy mouse. Suspected pathogen. Dead mouse. The pathogen should always be found in the body of a sick organism and should not be found in a healthy one.. Suspected pathogen. Dead mouse. Injection of organisms from pure culture. Healthy mouse. Suspected pathogen grown in pure culture.. The pathogen must be isolated and grown in the laboratory in a pure culture.. Pathogen. When purified pathogens are placed in a new host, they should cause the same disease that infected the host.. Dead mouse. The very same pathogen should be reisolated from the second host. And it should be the same as the original pathogen..

(39) The Line of Defense • First Line of Defense – Barriers (Skin & Mucous Membranes). • Second Line of Defense – Nonspecific Immunity. • Third Line of Defense – Specific Immunity (The Immune System).

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(41) Second Line of Defense • Inflammatory Response – A series of reactions that suppress infection and speed recovery. • Phagocytes – Ingest and destroy pathogens and foreign matter.

(42) Skin. Wound Phagocytes move into the area and engulf the bacteria and cell debris. Bacteria enter the wound Capillary.

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(44) Second Line of Defense • Macrophage – Engulf pathogens and cellular debris. • Interferon – A protein released by cells infected with viruses; causes nearby cells to make protein that helps resist viral infection.

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(46) Third Line of Defense • Specific Immunity—Immune System – Lymphocytes • White blood cells of the immune system. – B Cells • Lymphocytes made in bone marrow (development completed in spleen). – T Cells • Lymphocytes made in bone marrow (development completed in thymus).

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(48) Third Line of Defense • Antigens – Any substance that the immune system does not recognize as part of the body. • Antibodies – Y-shaped molecules that are released by the blood and activated to destroy toxins.

(49) Antigenbinding sites. Antigen. Antibody.

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(51) Vaccinations • Vaccination – The introduction of antigens into the body to cause immunity (it usually involves an injection or inoculation under the skin). • Vaccine – A solution that contains dead or weakened pathogen or material from a pathogen.

(52) Vaccinations • Inactivated virus – Is not able to replicate in a host. • Attenuated virus – Is a weakened form of the disease that cannot cause disease.

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(54) Smallpox • Smallpox was completely eradicated through vaccinations. The WHO started smallpox eradication program in 1967. The last case was in 1977. It was declared eradicated in nature in 1980 by the WHO.

(55) Antibiotics • Antibiotics can only be used to treat bacterial infections • They affect bacteria by interfering with certain cellular activities • Penicillin was the first antibiotic (discovered by Alexander Fleming in 1928).

(56) Antibiotic Resistance • Antibiotic resistance is a major concern for the medical community • MRSA and antibiotic resistant TB are of particular concern.

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