Rhizospheric bacteria exhibiting antagonistic effects are a good source for the production of antibiotics. The antibiotics produced are naturally bactericidal or bacteriostatic in nature. In the present investigation thirty-five rhizospheric bacteria were isolated from different soil samples. Agar well diffusion method, streak agar method, disc diffusion method and biochemical tests were performed to screen the ten antibiotic-producing bacteria. Among them, strain JRR34 selected on the basis of primary antagonistic activity was identified as Streptobacillus sp. Media optimisation was done to ensure maximum production of secondary metabolites. Streptobacillus sp. JRR34 showed good inhibitory activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The ethyl crude extract of Streptobacillus sp. JRR34 rhizobacteria possessing good antagonistic activity against a wide range of pathogenic bacteria can be a vital source of novel antibiotics.
Antibiosis, crude extract, pathogens, rhizospheric bacteria, secondary metabolites, Streptobacillus
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