PMID:11442826

Citation	Martin, AC, Wadhams, GH and Armitage, JP (2001) The roles of the multiple CheW and CheA homologues in chemotaxis and in chemoreceptor localization in Rhodobacter sphaeroides. Mol. Microbiol. 40:1261-72
Abstract	Rhodobacter sphaeroides has multiple homologues of most of the Escherichia coli chemotaxis genes, organized in two major operons and other, unlinked, loci. These include cheA1 and cheW1 (che Op1) and cheA2, cheW2 and cheW3 (che Op2). We have deleted each of these cheA and cheW homologues in-frame and examined the chemosensory behaviour of these strains on swarm plates and in tethered cell assays. In addition, we have examined the effect of these deletions on the polar localization of the chemoreceptor McpG. In E. coli, deletion of either cheA or cheW results in a non-chemotactic phenotype, and these strains also show no receptor clustering. Here, we demonstrate that CheW2 and CheA2 are required for the normal localization of McpG and for normal chemotactic responses under both aerobic and photoheterotrophic conditions. Under aerobic conditions, deletion of cheW3 has no significant effect on McpG localization and only has an effect on chemotaxis to shallow gradients in swarm plates. Under photoheterotrophic conditions, however, CheW3 is required for McpG localization and also for chemotaxis both on swarm plates and in the tethered cell assay. These phenotypes are not a direct result of delocalization of McpG, as this chemoreceptor does not mediate chemotaxis to any of the compounds tested and can therefore be considered a marker for general methyl-accepting chemotaxis protein (MCP) clustering. Thus, there is a correlation between the normal localization of McpG (and presumably other chemoreceptors) and chemotaxis. We propose a model in which the multiple different MCPs in R. sphaeroides are contained within a polar chemoreceptor cluster. Deletion of cheW2 and cheA2 under both aerobic and photoheterotrophic conditions, and cheW3 under photoheterotrophic conditions, disrupts the cluster and hence reduces chemotaxis to any compound sensed by these MCPs.
Links	PubMed
Keywords	Aerobiosis; Bacterial Proteins/physiology; Cell Polarity; Chemotaxis/physiology; Escherichia coli Proteins; Gene Deletion; Green Fluorescent Proteins; Luminescent Proteins/genetics; Luminescent Proteins/metabolism; Membrane Proteins/genetics; Membrane Proteins/metabolism; Multigene Family; Propionic Acids; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Rhodobacter sphaeroides/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RHOSH:CHEA		GO:0006935: chemotaxis	ECO:0000315:		P		Figure 2 shows the behavior of wild type and mutant strains in a tethered cell assay. Conditions are varied between Aerobic and Photoheterotrophic. In each assay, the addition or removal of 1 mM propionate is shown.	complete
RHOSH:CHEW		GO:0006935: chemotaxis	ECO:0000315:		P		Figure 2 shows the behavior of wild type and mutant strains in a tethered cell assay. Conditions are varied between Aerobic and Photoheterotrophic. In each assay, the addition or removal of 1 mM propionate is shown.	complete

References

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