Abstract
BackgroundIn general, chemotaxis in Rhizobium has not been well characterized. Methyl accepting chemotaxis proteins are sensory proteins important in chemotaxis of numerous bacteria, but their involvement in Rhizobium chemotaxis is unclear and merits further investigation.ResultsA putative methyl accepting chemotaxis protein gene (mcpG) of Rhizobium leguminosarum VF39SM was isolated and characterized. The gene was found to reside on the nodulation plasmid, pRleVF39d. The predicted mcpG ORF displayed motifs common to known methyl-accepting chemotaxis proteins, such as two transmembrane domains and high homology to the conserved methylation and signaling domains of well-characterized MCPs. Phenotypic analysis of mcpG mutants using swarm plates did not identify ligands for this putative receptor. Additionally, gene knockouts of mcpG did not affect a mutant strain's ability to compete for nodulation with the wild type. Notably, mcpG was found to be plasmid-encoded in all strains of R. leguminosarum and R. etli examined, though it was found on the nodulation plasmid only in a minority of strains.ConclusionsBased on sequence homology R. leguminosarum mcpG gene codes for a methyl accepting chemotaxis protein. The gene is plasmid localized in numerous Rhizobium spp. Although localized to the sym plasmid of VF39SM mcpG does not appear to participate in early nodulation events. A ligand for McpG remains to be found. Apparent McpG orthologs appear in a diverse range of proteobacteria. Identification and characterization of mcpG adds to the family of mcp genes already identified in this organism.
Highlights
IntroductionMethyl accepting chemotaxis proteins are sensory proteins important in chemotaxis of numerous bacteria, but their involvement in Rhizobium chemotaxis is unclear and merits further investigation
Chemotaxis in Rhizobium has not been well characterized
Results methyl accepting chemotaxis protein gene (mcpG) Cloning and Gene Characterization mcpG was identified in a R. leguminosarum VF39SM cosmid library using a DNA probe derived from the highly
Summary
Methyl accepting chemotaxis proteins are sensory proteins important in chemotaxis of numerous bacteria, but their involvement in Rhizobium chemotaxis is unclear and merits further investigation. Using a process termed chemotaxis, motile bacteria are capable of sensing their external environment and responding appropriately by moving towards increasing concentrations of nutrients and away from increasing concentrations of toxic compounds. The chemotaxis signaling pathway has been well characterized due to extensive studies using the model organism Escherichia coli, as well as detailed molecular characterization in numerous taxonomically distinct bacteria [1,2]. Methyl accepting chemotaxis proteins (MCPs) play key roles in the chemotactic response of many bacteria. These sensor proteins have N-terminal domains that detect attractants and repellents. The effect is alteration of swimming behavior by changing the direction of flagellar rotation or, in some cases, the speed of flagellar rotation, resulting in movement towards higher (page number not for citation purposes)
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