Mycosubtilin Overproduction by Bacillus subtilis BBG100 Enhances the Organism's Antagonistic and Biocontrol Activities

TL;DR

This study engineered a Bacillus subtilis strain to overproduce mycosubtilin, significantly enhancing its antagonistic and biocontrol activities against plant pathogens and improving seed germination and seedling growth.

Contribution

The paper introduces a genetic modification to increase mycosubtilin production in Bacillus subtilis, boosting its biocontrol efficacy and revealing new forms of the lipopeptide.

Findings

15-fold increase in mycosubtilin production

Enhanced antagonistic activity against fungi and yeasts

Improved seed germination and seedling growth

Abstract

A Bacillus subtilis derivative was obtained from strain ATCC 6633 by replacement of the native promoter of the mycosubtilin operon by a constitutive promoter originating from the replication gene repU of the Staphylococcus aureus plasmid pUB110. The recombinant strain, designated BBG100, produced up to 15-fold more mycosubtilin than the wild type produced. The overproducing phenotype was related to enhancement of the antagonistic activities against several yeasts and pathogenic fungi. Hemolytic activities were also clearly increased in the modified strain. Mass spectrometry analyses of enriched mycosubtilin extracts showed similar patterns of lipopeptides for BBG100 and the wild type. Interestingly, these analyses also revealed a new form of mycosubtilin which was more easily detected in the BBG100 sample. When tested for its biocontrol potential, wild-type strain ATCC 6633 was almost ineffective for reducing a Pythium infection of tomato seedlings. However, treatment of seeds with the BBG100 overproducing strain resulted in a marked increase in the germination rate of seeds. This protective effect afforded by mycosubtilin overproduction was also visualized by the significantly greater fresh weight of emerging seedlings treated with BBG100 compared to controls or seedlings inoculated with the wild-type strain.