Secondary metabolites from endophytic bacteria and evaluation of their antibacterial potential

The objective of this study was to isolate endophytic bacteria from Cymbopogon citratus (lemon grass) leaves and investigate their antibacterial activity against bacterial pathogens. Fresh leaves of C. citratus were collected from Madhavaram botanical garden. Isolation of endophytic bacteria was done by standard procedure. Identification of the bacterial isolates were performed by morphological and Gram's staining characteristics. A total of 7 bacterial isolates from the leaves of C. citratus were isolated. Based on the morphological and Gram staining characteristics, 3 bacterial strains were selected for the further studies, which is well differentiated with others. The chloroform extracts of selected 3 bacterial strains were screened for their antibacterial potential against three bacterial pathogens namely Klebsiella pneumoniae (MTCC3384), Staphylococcus aureus (MTCC3160) and Escherichia coli (MTCC443) by Kirby-Bauer disk diffusion method. The antibacterial study reveals that among the 3 selected bacterial strains, two strains namely Streptomyces sp. (EB2) and Bacillus sp. (EB3) showed potential antibacterial activity against all 3 tested pathogens with the zone of inhibition ranging from 11 to 15 mm; however, the bacterial strain Vibrio sp. (EB1) did not showed activity against all 3 tested pathogens. The positive control Amoxicillin showed zone of inhibition ranging from 12 to 18 mm and the negative control Chloroform did not express any zone of inhibition. In conclusion, the current study revealed that crude extracts of endophytic bacteria Streptomyces sp. (EB2) and Bacillus sp. (EB3) have potential antibacterial property