The phosphorylated regulator of chemotaxis is crucial throughout biofilm biogenesis in Shewanella oneidensis

Anne Boyeldieu,Vincent Méjean,Amine Ali Chaouche,Cécile Jourlin-Castelli,Flora Ambre Honoré,Moly Ba

doi:10.1038/s41522-020-00165-5

Anne Boyeldieu, Vincent Méjean + Show 4 more

Open Access

https://doi.org/10.1038/s41522-020-00165-5

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Abstract

The core of the chemotaxis system of Shewanella oneidensis is made of the CheA3 kinase and the CheY3 regulator. When appropriated, CheA3 phosphorylates CheY3, which, in turn, binds to the rotor of the flagellum to modify the swimming direction. In this study, we showed that phosphorylated CheY3 (CheY3-P) also plays an essential role during biogenesis of the solid-surface-associated biofilm (SSA-biofilm). Indeed, in a ΔcheY3 strain, the formation of this biofilm is abolished. Using the phospho-mimetic CheY3D56E mutant, we showed that CheY-P is required throughout the biogenesis of the biofilm but CheY3 phosphorylation is independent of CheA3 during this process. We have recently found that CheY3 interacts with two diguanylate cyclases (DGCs) and with MxdA, the c-di-GMP effector, probably triggering exopolysaccharide synthesis by the Mxd machinery. Here, we discovered two additional DGCs involved in SSA-biofilm development and showed that one of them interacts with CheY3. We therefore propose that CheY3-P acts together with DGCs to control SSA-biofilm formation. Interestingly, two orthologous CheY regulators complement the biofilm defect of a ΔcheY3 strain, supporting the idea that biofilm formation could involve CheY regulators in other bacteria.

Highlights

Bacteria can adopt either a planktonic or sessile lifestyle
Given that the CheA3 kinase and the CheY3 chemotaxis regulator of S. oneidensis play a key role during pellicle formation, we looked for their possible role in SSA-biofilm biogenesis
Overexpression of two diguanylate cyclase-encoding genes restores SSA-biofilm formation in the cheY3-deleted mutant strain We previously showed that CheY3 is able to interact with two diguanylate cyclases (DGCs), named PdgA and PdgB, in the context of pellicle formation

Summary

INTRODUCTION

Bacteria can adopt either a planktonic or sessile lifestyle. Both are highly regulated, as is the switch from one to another. The presence of either the wild-type cheY3 or cheY3D56E allele allowed the restoration of biofilm formation These results confirm that CheY3 phosphorylation is not carried out by CheA3 during the biogenesis of the SSA-biofilm. Few cells were visible under the microscope, most of which were motile (Fig. 1b) These results clearly indicate that the CheY3 chemotaxis regulator is absolutely required for SSA-biofilm biogenesis. Unlike its wild-type counterpart, the cheY3D56A allele encoding a non-phosphorylatable form of CheY3 was unable to restore SSA-biofilm formation in the ΔcheY3 background. This is reminiscent of that which occurs in the presence of the wild-type cheY3 allele, even if the increase is slightly lower in the presence of cheY3D56E (Fig. 3a) These results indicate that the phosphorylation of CheY3 is required for biofilm initiation to occur. This strongly suggests that CheY3 must be phosphorylated from the early to the late steps of SSA-biofilm

Boyeldieu et al 4 a

DISCUSSION

Findings

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