The predatory soil bacterium Lysobacter reprograms quorum sensing system to regulate antifungal antibiotic production in a cyclic-di-GMP-independent manner

Kaihuai Li,Gaoge Xu,Guichun Wu,Rongxian Hou,Fengquan Liu,Bo Wang

doi:10.1038/s42003-021-02660-7

Abstract

Soil bacteria often harbour various toxins to against eukaryotic or prokaryotic. Diffusible signal factors (DSFs) represent a unique group of quorum sensing (QS) chemicals that modulate interspecies competition in bacteria that do not produce antibiotic-like molecules. However, the molecular mechanism by which DSF-mediated QS systems regulate antibiotic production for interspecies competition remains largely unknown in soil biocontrol bacteria. In this study, we find that the necessary QS system component protein RpfG from Lysobacter, in addition to being a cyclic dimeric GMP (c-di-GMP) phosphodiesterase (PDE), regulates the biosynthesis of an antifungal factor (heat-stable antifungal factor, HSAF), which does not appear to depend on the enzymatic activity. Interestingly, we show that RpfG interacts with three hybrid two-component system (HyTCS) proteins, HtsH1, HtsH2, and HtsH3, to regulate HSAF production in Lysobacter. In vitro studies show that each of these proteins interacted with RpfG, which reduced the PDE activity of RpfG. Finally, we show that the cytoplasmic proportions of these proteins depended on their phosphorylation activity and binding to the promoter controlling the genes implicated in HSAF synthesis. These findings reveal a previously uncharacterized mechanism of DSF signalling in antibiotic production in soil bacteria.

Highlights

Soil bacteria often harbour various toxins to against eukaryotic or prokaryotic
We found that unlike the Xanthomonas RpfC/RpfG-Clp signaling pathway, the L. enzymogenes RpfG protein interacts with three hybrid two-component system (HyTCS) proteins (HtsH1, HtsH2, and HtsH3) to regulate the production of the antifungal factor HSAF and describe their regulatory functions in soil bacteria
Quantitative analysis revealed that RpfG-maltose binding protein (MBP) exhibited a high level of activity for the degradation of c-di-GMP with 100% degraded at 5 min after initiation of the reaction in comparison to the MBP enzyme as a control (Fig. 1c)

Summary

Introduction

Soil bacteria often harbour various toxins to against eukaryotic or prokaryotic. Diffusible signal factors (DSFs) represent a unique group of quorum sensing (QS) chemicals that modulate interspecies competition in bacteria that do not produce antibiotic-like molecules. The molecular mechanism by which DSF-mediated QS systems regulate antibiotic production for interspecies competition remains largely unknown in soil biocontrol bacteria. We show that the cytoplasmic proportions of these proteins depended on their phosphorylation activity and binding to the promoter controlling the genes implicated in HSAF synthesis These findings reveal a previously uncharacterized mechanism of DSF signalling in antibiotic production in soil bacteria. We found that unlike the Xanthomonas RpfC/RpfG-Clp signaling pathway, the L. enzymogenes RpfG protein interacts with three hybrid two-component system (HyTCS) proteins (HtsH1, HtsH2, and HtsH3) to regulate the production of the antifungal factor HSAF and describe their regulatory functions in soil bacteria. The HtsH1, HtsH2, and HtsH3 functions likely represent a common mechanism that helps establish signaling specificity in bacteria for interspecies competition

Methods

Results

Conclusion