BIOACTIVE SECONDARY METABOLITES PRODUCTION BY TERRESTRIAL BACILLUS CIRCULANS STRAINS

Abstract

Screening for antagonistic microorganisms is a promising tool for discovering new antimicrobial metabolites. In this study, two Bacillus sp. (HU6 and HU8) were isolated from soil and assessed for their antimicrobial activity by the agar-well diffusion method against different human pathogens. According to general characteristics, morphology, and physio-chemical properties of the isolates they were identified as Bacillus circulans. Both strains exhibited a broad spectrum of activity against Gram positive and Gram negative pathogenic bacteria. The highest antimicrobial activity was achieved from ethyl acetate extract of B. circulans HU6 against E. coli where the inhibition zone was 26.3 ± 0.82 mm. The bioactivity of the isolates extract was not affected when subjected to heat treatment or proteolytic digestion suggesting that the nature of the active metabolites was not proteinaceous. The  GC/MS analysis of the extracts revealed the presence of 4 bioactive compounds: Pyrrolo[1,2-a]pyrazine-1,4-dione, Trans-13-octadecenoic acid, 2,5-piperazine dione,3,6-bis (2-methyl propyl), and cis-13-eicosenoic acid.