cide is available for BFB, our works will continue to commercialise those promising antagonists to be effectively used as seed treatments in nurseries. Acidovorax citrulli, the agent of seedling blight and fruit blotch of cucurbits, can affect several plant organs during different stages of develop- ment. Therefore, the selection of biological control agents for the disease control should consider differ- ent disease stages to get more reliable results. The bacteria Curtobacterium flaccumfaciens, Microbac- terium oxydans, Pseudomonas oryzihabitans, and Pseudomonas fluorescens were highly efficient for treating watermelon seeds. Thus, the application of these antagonistic bacteria should be combined with other control strategies such as resistant cultivars, disinfection or fermentation of seeds, spray of copper compounds. Those antagonists should be applied under greenhouse or field conditions to compare their efficacy on BFB development.
Plant-root exudates-rhizosphere microbes form a cyclical interaction , and rhizosphere microorganisms convert organic nutrients of root exudates into inorganic nutrients to facilitate plant utilization, thus affecting comprehensive indicators of plants    . By analyzing the changes of root ex- udates of tobacco under the effect of different microbes, it was found that when the pathogenic microorganisms in the rhizosphere microorganisms increased, the root exudates of tobacco augmented evidently. When the abundance of pa- thogens of bacterial wilt in the rhizosphere increased, the organic acids, amines and lipids increased by 32.78%, 13.35% and 15.76% respectively among which organic acids displayed the greatest rise, increased by 10.11%; followed by amine, increased by 6.09%. When the pathogen of bacterial wilt was inhibited by the active substances of its antagonistic bacteria, the root exudates changed sig- nificantly, and there were newly 19 kinds of elements added, but 1-butanol, pro- pionic acid, isophthalic acid, myristic acid, phenethyl imine acid, sebacic acid and cyclopropene disappeared. Although the mechanism of effect of propionic acid, myristic acid, ethyl benzoate and sebacic acid was unclear, studies have confirmed that terephthalic acid, isophthalic acid and benzoic acid are allelo- pathic substances to many crops. They are crucial substance that cause conti- nuous cropping obstacles     . When the abundance of pa- thogen of bacterial wilt and its antagonist changed in the rhizosphere, the changes of root exudates were similar to the treatment of bacterial wilt and its antagonist.
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How to cite this paper: Preecha, C., Wi- sutthiphaet, W. and Seephueak, P. (2018) Occurrence of Canker Caused by Xantho- monas axonopodis pv. citri on Pummelo (Citrus maxima (Burm.) Merr.) Cultivar. Tabtimsiam in Nakhon Si Thammarat Province, Thailand and Screening Fungi- cides, Antibiotics and Antagonistic Bacteria against X. a. pv. citri in Vitro. Journal of Geoscience and Environment Protection, 6, 1-7.
In the soil environment different interactions between microorganisms on the one hand and between plants and microorganisms on the other take place. Soil bacteria and fungi have a positive or a harmful effect on the growth and develop- ment of plants (Czaban et al. 2007, Abdulkadir and Waliyu 2012, Patkowska and Konopiński 2013a). Antagonistic bacteria Pseudomonas spp. and Bacillus spp. play a big role in limiting the occurrence of soil-borne fungi (Patkowska 2009, Sivanantham et al. 2013). The enumerated bacteria are distinguished by a big ability to inhibit the de- velopment of pathogens through the competition for nutrients elements and the space, antibiosis, production of lytic enzymes, HCN production and decomposition of toxins (Krid et al. 2010, Abdulkadir and Waliyu 2012).
Patkowska E. (2018): Antagonistic bacteria in the soil after Daucus carota L. cultivation. Plant Soil Environ., 64: 120–125. The studies determined the effect of bacteria Bacillus spp. and Pseudomonas spp. isolated from the soil after car- rot cultivation on pathogenic fungi Altenaria dauci, A. radicina, Fusarium oxysporum, F. solani, Rhizoctonia solani and Sclerotinia sclerotiorum. A field experiment on carrot cultivation considered different intercrop plants (rye, buckwheat, white mustard, sunflower). Rye and buckwheat were the most conducive to the growth of Bacillus spp. and Pseudomonas spp. Those bacteria were the most effective in inhibiting the growth of F. solani, F. oxysporum and R. solani. The antagonistic effect of soil-borne Bacillus spp. and Pseudomonas spp. towards the tested fungi was the largest after the application of rye and white mustard as intercrop plants in the cultivation of carrot. Buckwheat and sunflower showed a slightly smaller influence on the antagonistic activity of the studied bacteria. Bacillus ssp. had a significantly lesser antagonistic effect than Pseudomonas ssp.
each year (9). Likewise, bacterial-based bio-control products have now been commercially developed for control of fungal spoilage of food products and agricultural commodities (14). It has been shown that production of an extremely wide array of bioactive compounds by bacteria and their potential for use in biocontrol programs is completely dependent on parameters such as taxonomical position and physiological characters (i.e. species, varieties and growth cycle), geographic condition, soil composition, etc. So, screening of a large number of bacteria from different geographic locations may increase the chance of finding novel bioactive compounds with broad spectrum antifungal activity.
Ten isolates of Erwinia carotovora ssp. carotovora (Ecc) were isolated from infected potato tubers of Picasso, Sante, and Nevskiy varieties collected from different regions in Kyrgyzstan. Isolates were identified as Erwinia carotovora ssp. carotovora (Ecc) by standard bacteriological techniques and pathogenicity tests on tubers and also by PCR analyses. Tests on the pathogenicity of E. caro- tovora ssp. carotovora (Ecc) strains to host plants by artificial inoculation have shown a high sen- sibility of the Picasso variety. As a result, five isolates were chosen, three isolates (EcPo1, EcPo2, and Eco3) were highly pathogenic, while two isolates (Eco4 and Eco5) were weakly pathogenic. The antagonistic bacteria, Streptomyces diastatochromogenes strain sk-6, and Streptomyces gra- minearuss strain sk-2, have a highly significant effect on soft rot bacteria isolates (Ecc), more than the other tested antagonistic organisms in vitro screening biotests. The Streptomyces diastatoch- romogenes sk-6 was selected for the control assay of storage potatoes against the most common soft rot bacterial strain in Kyrgyzstan, Erwinia carotovora sp. carotovora EcPo2. The pretreatment of potato tubers with antagonistic bacteria successfully prevented the initial infection multiplica- tion of soft rot bacteria and reduced soft rot disease of potatoes in storage. These results justify selection of the dose 10 6 cells/ml of bacteria Streptomyces diastatochromogenes sk-6 for use in
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The present study was aimed to isolate the antagonistic bacteria from marine microalgal sample(Chlorella salina), the isolated bacterial strains were identified , screened for their bioactivity against the aquatic pathogens, to extract and characterize the compounds produced by antagonistic bacteria. Among the isolates Vibrio sp.MMB2 strain and Pseudomonas sp. had good antagonistic property against all tested pathogens. The maximum biogenic activity was occurred at the stationary phase culture. The metabolites extracted from Vibrio sp. MMB2 was showed highest zone of inhibition against A.hydrophylla .One active fraction was isolated by TLC. The functional group was identified through FTIR analysis ,the bacterial metabolites contains Nitrogenous compound as a functional groups. The Partially purified CFNS (bacteriocin) of Vibrio sp. MMB2 was showed two distinct bands on SDS-PAGE, its high molecular weight of antimicrobial peptides. The bacterial metabolites effectively controlled the pathogens at broad range, to compare commercial antibiotics.
The presented studies showed, that oats and com- mon vetch had the most positive effect on the popula- tions of antagonistic bacteria and their antagonistic activity towards pathogenic fungi. According to Gamliel et al. (2000), the development of Bacillus spp. and Pseudomonas spp. can be favored by second- ary metabolites of the mulching plants introduced into the soil. As reported by Krid et al. (2010) and Verma et al. (2012), high antagonistic activity of those bacteria is connected with their ability to produce antibiotics or siderophores. Those compounds have a fungistatic or fungicidal effect.
Genomic DNA was extracted from the selected antagonistic bacterial isolates using a DNA extraction kit (Thermo Scientific, Waltham, USA). To identify antagonistic bacteria, 16S rRNA gene sequencing was performed. Using bacterial universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'- GGTTACCTTGTTACGACTT -3'), the 16S rRNA gene fragment was amplified under following PCR conditions: one cycle of 95°C for 5 min followed by 28 cycles of 95°C for 1 min, and annealing at 58°C for 50s with extension at 72°C for 50s, and a final extension step at 72°C for 10 min. PCR products were purified using PCR purification kit (Thermo Scientific, Waltham, USA), and sequenced commercially (Macrogen, South Korea). 16S rRNA gene sequences obtained were blast using the EzTaxon server (http://eztaxon- e.ezbiocloud.net) (Kim et al., 2012) to identify antagonistic bacteria. Phylogenetic positions of the antagonistic bacteria were confirmed using CLUSTALX (Thompson et al., 1997) multiple alignments of the bacterial sequences were performed and BioEdit software (Hall, 1999) was used to edit the gaps. The neighbour-joining method in the MEGA6 Programme was used for construction of the phylogenetic tree based on the 16S rRNA gene sequences (Tamura et al., 2013).
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Antagonistic microorganisms in the biological control of the disease induced by Fusarium oxysporum in tomato although systems have been developed to study other host pathogen biocontrol agent interactions . In agriculture, phytopathogenic fungi can causes plant disease and much loss of crop yields. Pesticide or used to control the plant disease. However, agrochemical treatment causes environmental pollution and diseases. Microorganisms act as biocontrol agents have high potential to control the plant pathogens and no effective on the environmental or other non-targeted organisms. There are numerous report on the potential uses of biocontrol agent as replacement for Agrochemical.Tomato black root rot caused by Fusarium oxysporum. It is one of the destrutive tomato disease in worldwide.
methods. For DNA extraction from the mentioned isolates, lysozyme enzyme was used. First, 1 ml of the culture medium containing the bacteria from the 24h cultivation of the lactobacilli was poured into a 1.5 ml microtube, and centrifuged at 3500 rpm for 8 min. Following the centrifuge, the top phase was removed and the precipitates were washed three times with the TEN (NaCl 150 mm, EDTA 100 mm, Tris) buffer, each time at 3000 rpm for 5 min. A buffer composed of 200 μl TEN buffer and 10 μl of lysozyme enzyme was added to the resulting precipitates, and they were incubated at 37°C for 30 min. following the passage of this time, 75 μl SDS was added and after sampling, incubated at 75°C for 30 min. In the next stage, 250 μl equilibrated phenol was added to the solution and then incubated at 52°C for 30 min. next, 250 μl of chloroform was added to the solution and mixed well. Thereafter, the solution of interest was centrifuged at 12000 rpm for 15 min. Next, the aqueous phase was transferred to a new vial, with chloroform being added at a volume the same as the dragged aqueous solution. Following several times of vigorous shaking of the solutions, the vials were placed inside a centrifuge for 15 min at 12000 rpm, where the top phase was transferred to a new vial. Cold Isopropanol was added with a volume equal to the volume of the top phase and the vials were centrifuged at 13000 rpm for 15 min at. The top phase was then fully removed, and 400 μl cold ethanol was added to the resulting precipitates. In the next stage, the vials were exposed to room temperature for 15 min and then placed inside an open-air incubator at 42°C for 15 min, so that the alcohol would evaporate. Finally, the precipitates were dried at room temperature. Polymerase Chain Reaction (PCR) was employed to amplify bacterial 16S rRNA gene. The master mix for the PCR was prepared as follow: 3μL of 10× PCR buffer, 1μL of 25mM MgCl 2 , 3μLof 10mM dNTP mix, 0.5μL
Novel antibiotic and other bioactive compounds lead molecules which discovered in pharmaceu- tical interest by using new bacterial secondary metabolite screening method is becoming increa- singly fruitful. Know a day there is wide accep- tance of microbes are practically unlimited sources of new secondary metabolism with many pharma- ceutical therapeutic applications (Wang, et al., 2017). Out of them actinomycetes become a promi- nent position because of their diversity and had proven their ability to produce new substances which recognized as Streptomyces. They are aero- bic, exospore forming Gram-positive bacteria which have DNA with a high G+C amount (69- 73%). They form a branching substrate with aerial mycelia and widely distributed in soil (Al-Mahdi, 2006). In the past decades, the needs for drugs is increased to control new illness or resistant strains of pathogenic microorganisms which stimulated to look for unconventional new sources of bioactive metabolites. Soil is found to be an attractive field
them to form a barrier that prevents pathogenic bacteria from colonizing. The potential to bind closely with other bacteria is correlated with co-aggregation. This aggregation ability of LAB species in the presence of pathogenic microbes may create a protective mechanism to stop pathogens from colonizing in the human gut . Pathogens cause serious illness to humans, particularly when they can colonize and control the human gut .Co- aggregation is an important approach for evaluating the close association between LAB and pathogenic bacteria, as LAB has surface binding proteins specific to surfaces and bacteria. In this study, All the tested LAB isolates were found excellent in co-aggregating with pathogenic strain S. aureus(Fig 3). The co-aggregation with pathogenic strain enhances the LAB‟s potential probiotic property which makes them efficient in preventing colonization by patho- genic bacteria. Studies indicated that the LAB‟s ability to co- aggregate in the presence of gut pathogens would improve the LAB‟s probiotic properties. This finding confirms the potential probiotic properties of LAB isolates. This study is in line with previously documented results by, , , , .
A volume of 100 µl of inoculum suspension previously adjusted to 0.5 McFarland standard of each indicator bacteria was swabbed evenly on prepoured sterilized nutrient agar plates set for the disc diffusion assay. The lid was left ajar to allow the absorption of excess surface moisture for 10mins before placing the sterile discs. Sterile 5 mm diameter discs were prepared using Whatmann No. 1 filter paper and placed on bacteria swabbed nutrient agar plates equidistantly round the margin of Petridish. 10 µl of cell free supernatant from nutrient broth were dispensed on the disc. The plates were incubated at 37°C for 24 hrs. At the end of the incubation period, the antagonistic activity was recorded as the width of the clear inhibition zone formed around the disc (diameter of inhibition zone plus diameter of the disc). The values are the means of three independent experiment performed in triplicate .
The soil samples collected from Baramati regions showed presence of notable amount of pigment producing bacterial diversity. These bacteria are found to produce wide range of colours including yellow, red, orange, purple etc. Bacterial strain producing blue color pigment pyocyanin was identified morphologically and 16S rDNA technique as P. aeruginosa. This study suggested that morphological and biochemical (API) methods were found effective in identification of bacterial strain and these results can be confirmed by molecular identification techniques 16s rDNA. The selected P. aeruginosa JCM 5962(T) found to produce pyocyanin; confirmed by spectroscopic studies. The produced pigment can be successfully purified by gel chromatography techniques. All the parameters for pyocyanin production can be optimized by classical approach. The organism
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In addition, our study suggests that antagonistic effect of metformin on cisplatin-induced cell toxicity could also be through increase in the expression of Akt. Akt is a serin-threonin kinase which has a paramount importance in cell survival and apoptosis. This protein exerts its antiapoptotic effect directly through phosphorylation and inactivation of Bad, forkhead transcription factors, c-raf, and caspase 9 32-35 and indirectly through
Soybean (Glycine max (L.) Merril) is an Asiatic leguminous plant, occupying large acreages of land worldwide for its oil and protein. However, due to extreme diversity of pathogens and serious diseases severe plant losses and yield reductions are common in susceptible cultivars of soybean . Inspite of increased numbers of reports about beneficial traits of endophytic microbes to crop plants protecting their host against predators and pathogens, there is the dearth of information regarding combined effects of different endophytic bacteria on the management of soil borne fungal pathogens in soybean (Glycine max). Hence, with the view of plant health and productivity the present studies on screening of antagonistic and plant growth promoting potentials of indigenous bacterial endophytes of soybeans (CV.JS-353) have been carried out.
Hoffman A, Weyens N, Barac T, Vangronsveld J, van der Lelie D. Genome survey and characteri- zation of endophytic bacteria exhibiting a benefi- cial effect on growth and development of poplar trees. Appl Environ Microbiol 2009; 75:748-757 6. Alström S. Characteristics of bacteria from oilseed rape in relation to their biocontrol activity against Verticillium dahliae. J Phytopathol 2001; 149:57- 64
Different biological control agents are used to fight various pathogens or even harmful organisms in different environments. Among these agents, a wide range of bacteria belonging to the genus Pseudomonas spp are capable to produce a large number of secondary metabolites with antibacterial activity. The main aim of the present work is the evaluation of the antagonistic activity of Ps. aeruginosa ATCC 27853 against pathogenic bacteria strains such as E. coli ATCC 25921, P. mirabilis ATCC 12453, B. subtilis ATCC 6633 and B. cereus ATCC 11778 by the using agar well diffusion method and by the study of the bacterial growth in the absence and in the presence of the supernatant of Ps. aeruginosa ATCC 27853. In order to characterize the molecules responsible for the antagonistic activity of Ps. aeruginosa ATCC 27853, various parameters such as temperature, pH, and incubation time has been investigated. The obtained results showed that the tested antagonistic activity of Ps. aeruginosa ATCC 27853 against, S. aureus, Enterobacter, S. typhi, P. vulgaris and B. subtilus ATCC6633 has manifested an excellent antibacterial activity with a maximal diameters of inhibition zone 32, 15, 14.14, 13 mm respectively. Furthermore, the study of bacterial growth of B. subtilus ATCC 6633 in the absence and in the presence of the supernatant of Ps. aeruginosa ATCC 27853 indicated a considerable biomass reduction accompanied with unbalanced growth after adding of the supernatant.