Pectobacterium brasiliense 1692 Chemotactic Responses and the Role of Methyl-Accepting Chemotactic Proteins in Ecological Fitness

Collins Kipngetich Tanui; Divine Yutefar Shyntum; Precious K Sedibane; Daniel Bellieny-Rabelo; Lucy N Moleleki

doi:10.3389/fpls.2021.650894

Pectobacterium brasiliense 1692 Chemotactic Responses and the Role of Methyl-Accepting Chemotactic Proteins in Ecological Fitness

Front Plant Sci. 2021 Apr 22:12:650894. doi: 10.3389/fpls.2021.650894. eCollection 2021.

Authors

Collins Kipngetich Tanui¹, Divine Yutefar Shyntum¹, Precious K Sedibane^{1

2}, Daniel Bellieny-Rabelo¹, Lucy N Moleleki^{1

2}

Affiliations

¹ Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa.
² Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.

Abstract

To adapt to changing environmental niches, bacteria require taxis, a movement toward or away from a stimulus (ligand). Chemotaxis has been studied in some members of the Soft Rot Pectobacteriaceae (SRP), particularly members of the genus Dickeya. On the contrary, there are fewer studies on this topic for the other genus in the SRP group, namely Pectobacterium. This study evaluated chemotactic responses in Pectobacterium brasiliense (Pb 1692) to various ligands. A total of 34 methyl-accepting chemotactic proteins (MCPs) were identified in the Pb 1692 genome and the domain architectures of these MCPs were determined. Four Pb 1692 MCPs previously shown to be differentially expressed during potato tuber infection were selected for further functional characterization. Toward this end, Pb 1692 mutant strains each lacking either AED-0001492, AED-0003671, AED-0000304, or AED-0000744 were generated. Two of these mutants (AED-0001492 and AED-0003671), were attenuated in their ability to grow and respond to citrate and are thus referred to as MCP _cit2 and MCP _cit1 , respectively, while the other two, AED-0000304 (MCP _xyl ) and AED-0000744 (MCP _asp ), were affected in their ability to respond to xylose and aspartate, respectively. Trans-complementation of the mutant strains restored swimming motility in the presence of respective ligands. The four MCP mutants were not affected in virulence but were significantly attenuated in their ability to attach to potato leaves suggesting that ecological fitness is an important contribution of these MCPs toward Pb 1692 biology.

Keywords: Pectobacterium brasiliense; blackleg disease; chemotaxis; ecological fitness; methyl accepting chemotaxis proteins; soft rot; virulence.