Transcriptome investigation on the multicellular behavior of Bacillus velezensis Bs916 anchoring surfactin

Aims To provide valuable information for a comprehensive understanding of the multicellular behavior of Bacillus velezensis Bs916 regulated by surfactin and other natural signals by Transcriptome. Methods and results Transcriptomics revealed a distinct effect on gene expression alterations caused by disruption of the surfactin gene cluster(Delta srf) and 100 mu g/ml surfactin addition(Delta srf + SRF). A total of 1573 differential expression genes were identified among Bs916, Delta srf, and Delta srf + SRF and grouped into eight categories based on their expression profiles. RT-qPCR analysis of 30 candidate genes showed high consistency with those of transcriptome. Additionally, the expression of eight candidate genes regulated by surfactin in a dose-dependent manner was revealed by lacZ fusion. Based on the above evidence, we proposed that surfactin can act as an extracellular signal for monitoring biofilm formation in Bs916 by directly regulating the expression of AbrB, DegS-degU, and SinI-SinR, and indirectly regulating the phosphorylation of ComA and Spo0A. Conclusions The biofilm of Delta srf was unable to restore significantly by surfactin addition, combined inclusion of surfactin (SRF), exopolysaccharide (EPS), and gamma-poly-dl-glutamic acid (gamma-PGA), results in significant restoration of Delta srf biofilm formation, thereby a preliminary model was presented about the molecular mechanism by which the signaling molecule surfactin regulates Bs916 multicellular behavior.