AUTHOR=Xue Jian , Tong Tong , Wang Rui , Qiu Yibin , Gu Yian , Sun Liang , Xu Hong , Lei Peng 

TITLE=Secretion of poly-γ-glutamic acid by Bacillus atrophaeus NX-12 enhanced its root colonization and biocontrol activity

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.972393

DOI=10.3389/fmicb.2022.972393

ISSN=1664-302X

ABSTRACT=<p><italic>Bacilli</italic> are used as biocontrol agents (BCAs) against phytopathogens and most of them can produce poly-γ-glutamic acid (γ-PGA) as one of the major extracellular polymeric substances (EPSs). However, the role of γ-PGA in plant biocontrol is still unclear. In this study, <italic>Bacillus atrophaeus</italic> NX-12 (γ-PGA yield: 16.8 g/l) was screened, which formed a strong biofilm and has been proved to be a promising BCA against Cucumber <italic>Fusarium</italic> wilt. Then, the γ-PGA synthesis gene cluster <italic>pgsBCA</italic> was knocked out by CRISPR-Cas9n. Interestingly, the antifungal ability of γ-PGA synthetase-deficient strain NX-12Δ<italic>pgs</italic> (γ-PGA yield: 1.65 g/l) was improved <italic>in vitro</italic>, while the biocontrol ability of NX-12Δ<italic>pgs</italic> was greatly diminished <italic>in situ</italic>. Data proved that γ-PGA produced by NX-12 contributes to the biofilm formation and rhizosphere colonization, which effectively improved biocontrol capability. Taken together, these findings prove that the mechanism of γ-PGA promotes the colonization of NX-12 and thus assists in controlling plant diseases, which highlight the key role of γ-PGA produced by BCA in biocontrol.</p>