AUTHOR=Yu Yiyang , Yan Fang , Chen Yun , Jin Christopher , Guo Jian-Hua , Chai Yunrong 

TITLE=Poly-γ-Glutamic Acids Contribute to Biofilm Formation and Plant Root Colonization in Selected Environmental Isolates of Bacillus subtilis

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01811

DOI=10.3389/fmicb.2016.01811

ISSN=1664-302X

ABSTRACT=<p><italic>Bacillus subtilis</italic> is long known to produce poly-γ-glutamic acids (γ-PGA) as one of the major secreted polymeric substances. In <italic>B. subtilis</italic>, the regulation of γ-PGA production and its physiological role are still unclear. <italic>B. subtilis</italic> is also capable of forming structurally complex multicellular communities, or biofilms, in which an extracellular matrix consisting of secreted proteins and polysaccharides holds individual cells together. Biofilms were shown to facilitate <italic>B. subtilis</italic>–plant interactions. In this study, we show that different environmental isolates of <italic>B. subtilis</italic>, all capable of forming biofilms, vary significantly in γ-PGA production. This is possibly due to differential regulation of γ-PGA biosynthesis genes. In many of those environmental isolates, γ-PGA seems to contribute to robustness and complex morphology of the colony biofilms, suggesting a role of γ-PGA in biofilm formation. Our evidence further shows that in selected <italic>B. subtilis</italic> strains, γ-PGA also plays a role in root colonization by the bacteria, pinpointing a possible function of γ-PGA in <italic>B. subtilis</italic>–plant interactions. Finally, we found that several pathways co-regulate both γ-PGA biosynthesis genes and genes for the biofilm matrix in <italic>B. subtilis</italic>, but in an opposing fashion. We discussed potential biological significance of that.</p>