A non‐flagellated, predatory soil bacterium reprograms a chemosensory system to control antifungal antibiotic production via cyclic di‐GMP signalling

Abstract

Summary Lysobacter enzymogenes is a non‐flagellated, soil proteobacterium that secretes a diffusible antibiotic known as heat‐stable antifungal factor (HSAF) to kill nearby fungi for food. The genome of the model strain OH11 encodes a homologous Wsp system, which is generally deployed by flagellated bacteria to achieve flagella‐dependent outputs via a c‐di‐GMP‐FleQ complex, in which c‐di‐GMP is a ubiquitous dinucleotide second messenger and FleQ is a transcription factor (TF). Here, we show that the Wsp system in the non‐flagellated OH11 participates in a unique c‐di‐GMP‐dependent signalling pathway and forms a WspR‐CdgL binary complex to alter HSAF production, in which WspR and CdgL act as a c‐di‐GMP diguanylate cyclase (DGC) and a non‐TF binding protein respectively. We found that the phosphorylation of WspR activates its DGC activity and enhances c‐di‐GMP production while inhibiting HSAF biosynthesis. The phosphorylation of WspR also plays a key role in weakening WspR‐CdgL binding and HSAF generation. Interestingly, c‐di‐GMP binding to CdgL did not seem to induce the disassociation of the WspR‐CdgL complex. These observations, along with our earlier findings, lead us to propose a model in which L. enzymogenes re‐programs the Wsp system via c‐di‐GMP signalling to regulate HSAF biosynthesis for the benefit of ecological adaptation.

Coordinated control of the type IV pili and c‐di‐GMP‐dependent antifungal antibiotic production in Lysobacter by the response regulator PilR

“…LchD is a new addition to the network of c‐di‐GMP synthesizing and degrading enzymes involved in HSAF biosynthesis. This list includes the DGC WspR and two PDEs, LchP and RpfG (Xu et al., 2018, 2021). We recently showed that WspR directly interacts with the c‐di‐GMP‐binding coactivator CdgL (YajQ), which together with the transcription factor LysR activates the HSAF biosynthesis operon (Han et al., 2020; Xu et al., 2021).…”

“…However, incomplete (c.70%) restoration of the ΔpilR phenotype by the ΔlchD deletion points to the existence of yet another pathway through with PilR affects HSAF production (Figure 4). This list includes the DGC WspR and two PDEs, LchP and RpfG (Xu et al, 2018(Xu et al, , 2021. We recently showed that WspR directly interacts with the c-di-GMP-binding coactivator CdgL (YajQ), which together with the transcription factor LysR activates the HSAF biosynthesis operon (Han et al, 2020;Xu et al, 2021).…”

“…This list includes the DGC WspR and two PDEs, LchP and RpfG (Xu et al, 2018(Xu et al, , 2021. We recently showed that WspR directly interacts with the c-di-GMP-binding coactivator CdgL (YajQ), which together with the transcription factor LysR activates the HSAF biosynthesis operon (Han et al, 2020;Xu et al, 2021). Our finding that the second known c-di-GMP effector in L. enzymogenes, Clp, has a different dedicated DGC presents a striking example of nonoverlapping c-di-GMP signal transduction cascades regulating a common target, HSAF biosynthesis operon expression.…”

“…The genome of L. enzymogenes OH11 encodes 26 GGDEF, EAL, or HD-GYP domain proteins presumably involved in c-di-GMP synthesis or degradation (Ren et al, 2020). Three of these proteins, RpfG, LchP (both PDEs), and WspR (a DGC), regulate HSAF biosynthesis (Han et al, 2015;Xu et al, 2018Xu et al, , 2021 by means of two c-di-GMP-binding protein effectors, Clp and CdgL (Han et al, 2020;Xu et al, 2018). Clp is a transcription activator of the operon.…”

“…The c‐di‐GMP‐bound CdgL promotes disassociation of the CdgL‐LysR complex, which leads to lower HSAF operon expression. CdgL interacts with WspR, which is dedicated to control CdgL but not Clp loading with c‐di‐GMP (Xu et al., 2021).…”