Antimicrobial Activities of Natural Products from Bacillus Species Isolated from the Caspian Sea

Background and Research for discovery and development of new and effective antimicrobial agents has been raised due to increasing rate of numerous multi-drug resistant pathogens. Marine bacteria especially Bacillus species are a rich source of potentially versatile secondary metabolites with antimicrobial activities. In this study, sediments of the Caspian Sea were screened for natural products obtained from Bacilli spp. with antimicrobial activities. Marine sediments were collected from different locations of the Caspian Sea shores. To isolate Bacillus, diluted samples were inoculated on rich medium and incubated at 30 °C. Preliminary screening of the isolates was performed using cross steak method against Gram positive and Gram negative bacteria. In addition, crude extracts of the selected Bacillus spp.were screened for antimicrobial activity using Kirby-Bauer disc diffusion method by determining the growth inhibition zone. Of the sediments, 19 Bacillus spp. were isolated and screened for antimicrobial activities. In preliminary screening, seven Bacillus spp. showed good antibacterial activity against test bacteria and identified as selective isolates. Results in the secondary screening of the crude extract from cultures demonstrated good antibacterial and antifungal activities in active isolates. Bacillus spp. MT18 and MT24 exhibited more antimicrobial activities than the others. According to this study the sediments of the Caspian Sea are potentially rich in Bacillus spp. that are capable of producing secondary metabolites with antimicrobial activities and this requires further research.