AZ-130 Strain from Oil-Contaminated Soil of Azerbaijan: Isolation, Antibacterial Screening, and Optimization of Cultivation Conditions

The goal of the presented work was to isolate bacteria from oil-contaminated soils of Azerbaijan, screen them for their antibacterial activity, and determine the optimal conditions for production of the antibacterial compounds of interest, since unusual and previously unanalyzed sources are of significant interest for the isolation of bacterial strains with novel properties. This work resulted in isolation of 44 bacterial strains from an oil-contaminated soil sample collected in the Lokbatan settlement, which were analyzed for the presence of antibacterial activity against two gram-positive and one gram-negative opportunistic pathogenic strains using the growth inhibition assay. After initial screening, 3 strains showed an antibacterial activity against at least one test organism. Supernatant screening of strain AZ-130 revealed its strong anti-gram-positive activity. The isolate was identified as a Bacillus vallismortis strain (99%) by 16S rRNA gene sequencing. A search in APD3 showed that currently there are no known antibiotics produced by B. vallismortis. To further purify and characterize the antimicrobial compound produced by this strain, the growth conditions (medium, incubation temperature, and cultivation time) at which production of the antimicrobial compound reached the highest values were optimized. The effect of the components of four media at four different temperatures on the production of the AZ-130 biologically active molecule was investigated. The supernatants collected from AZ-130 cultures grown under appropriate conditions were purified and assayed for antibacterial activity against S. aureus by the growth inhibition and broth microdilution methods. Production of the AZ-130 active molecule reached its highest level when the strain was cultivated in a TB + 2% glucose medium for 2 days at a temperature of 32°C.