Khusro A, Preetam Raj J. P and Panicker S. G.
Bacteria launch stress response in adverse and unfavourable environmental conditions. Antimicrobials or antimicrobial agents are one of the stresses for the microorganisms. The aim of the present investigation was to determine the antagonistic activity of a novel bacterial strain under normal and stressed conditions against some of bacteria including human pathogens. The identification of bacterium as Bacillus subtilis strain KPA was confirmed by subjecting its amplicon (483 bp) to 16S rRNA gene sequence analysis and pairwise alignment through BLAST tool. A definite volume of antimicrobial agents such as Allium sativum, ampicillin and Mercuric chloride at their sub- MIC values was added to the lag phase culture of strain KPA in order to provide stress to bacteria. The antibacterial activity of strain KPA (both control and stressed) against Staphylococcus aureus, E.coli, Bacillus subtilis, Proteus vulgaris and Staphylococcus epidermidis was determined through agar well diffusion method. The extracellular proteins or peptides secreted by strain KPA, both in normal (control or non-treated) and stressed conditions (treated), were found to be ineffective against these microbes. The present study clearly indicates that antagonistic nature of the bacteria depends upon the type of strain, source of isolation and their genetic organization.
