A Bacteriocin with Broad Antimicrobial Activity Produced by Newly Isolated Nitrogen-Fixing Bacillus Strains

Recently re-emerging infections occur due to antibiotic-resistant bacteria. The use of bacteriocins as a substitute for currently used antibiotics is promising. The isolated nitrogen-fixing Bacillus bacteria might be a potential candidate strain as an alternative source of peptide antibiotics in the future. A total of 15 nitrogen-fixing Bacillus strains with antibacterial activity were isolated from soil samples. Bacteriocin-producing strains against the indicator strains were co-cultured and isolated. The antibacterial activity of bacteriocin was detected by spot-on-the lawn method with different bacteria. Effects of proteolytic enzymes, pH, and heat treatment on bacteriocin activity were also determined. All isolated spore forming Bacillus strains had an inhibitory effect on Listeria monocytogenes and Staphylococcus aureus. Some of them had an inhibitory effect on methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). None of them had an inhibitory effect on Gram-negative bacteria. The antimicrobial compounds produced by these novel strains were inactivated by the proteolytic enzymes which demonstrated their proteinaceous nature. These bacteriocins were also active in a wide range of pH and temperature. In the present study, new bacteriocin-producing nitrogen-fixing Bacillus strains with anti-MRSA and anti-VRE activity were isolated from the environment and their biochemical properties were determined.