Thuricin 7: A novel bacteriocin produced by Bacillus thuringiensis BMG1.7, a new strain isolated from soil

Aims: Detection and identification of new antagonistic activities towards Bacillus cereus and relatives. Methods and Results: Twenty Bacillus thuringiensis strains were screened for their capacity to express bacteriocin-like agents. Strain BMG1.7, isolated from soil, showed an antagonistic activity called thuricin 7. Thuricin 7 was active against several species of the genus Bacillus, including three of the four known B. thuringiensis/B. cereus bacteriocin producers, as well as against Streptococcus pyogenes and Listeria monocytogenes strains. Antimicrobial activity was lost after treatment with proteinase K. The active protein had an apparent molecular weight of 11.6 kDa, and was secreted at the end of the exponential growth phase. Thuricin 7 retained 55% of the activity after incubation at 98°C for 30 min. The mode of action of thuricin 7 was shown to be bactericidal and bacteriolytic. Conclusions: Thuricin 7 is a novel bacteriocin produced by a newly isolated Bacillus thuringiensis strain BMG1.7. Significance and Impact of the Study: The characteristics of thuricin 7 indicate that it is a new bacteriocin which may have interesting biotechnological applications due to its relatively large activity spectrum.