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 MCPcit2 and MCPcit1,
respectively, while the other two, AED-0000304 (MCPxyl) and AED-0000744 (MCPasp),
were affected in their ability to respond to xylose and aspartate, respectively. Transcomplementation
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.
