Evidence for two chemosensory pathways in Rhodobacter sphaeroides.

@article{citeulike:2402620, abstract = {In contrast to enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. Although a chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene, deletion of the entire chemotaxis operon had only minor effects on chemotactic behaviour under the conditions tested. Responses to sugars were enhanced in tethered cells but in all other chemotaxis assays behaviour of the operon deletion mutant was wild type. The mutant also showed wild-type responses to weak organic acids such as acetate and propionate, the dominant chemoattractants for this organism, under all conditions. This is in direct contrast to the enterics in which CheA, CheW and CheY are absolutely essential for taxis to PTS sugars, oxygen and MCP-dependent chemoeffectors. The operon deletion mutant was subjected to Tn5 transposon mutagenesis and new mutants selected using a chemotaxis and phototaxis screen. One mutant, JPA203, was non-chemotactic on swarm plates and showed inverted responses when tethered or subjected to changes in light intensity. Characterization of the Tn5 insertion in JPA203 identified a second chemotaxis operon in R. sphaeroides that contains homologues of cheY, cheA and cheR, the first homologue of cheB and two homologues of cheW. The new genes were labelled orf10, cheY(III), cheA(II) cheW(II), cheW(III), cheR(II), cheB and tlpC. When introduced into a wild-type background, deletion of cheA(II) produced a chemotaxis minus phenotype in R. sphaeroides, suggesting that cheA(II) forms part of a dominant chemotactic pathway, whereas the earlier identified operon plays only a minor role under laboratory conditions. The data presented here support the existence of two chemosensory pathways in R. sphaeroides, a feature that so far is unique in bacterial chemotaxis.}, address = {Department of Biochemistry, Oxford University, UK.}, author = {Hamblin, P. A. and Maguire, B. A. and Grishanin, R. N. and Armitage, J. P. }, citeulike-article-id = {2402620}, issn = {0950-382X}, journal = {Mol Microbiol}, keywords = {chemosensory, chemotaxis, pathways, rhodobacter, sphaeroides}, month = {December}, number = {5}, pages = {1083--1096}, posted-at = {2008-02-20 12:03:37}, priority = {3}, title = {Evidence for two chemosensory pathways in Rhodobacter sphaeroides.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/9426144}, volume = {26}, year = {1997} }

TY - JOUR ID - citeulike:2402620 L3 - citeulike-article-id:2402620 TI - Evidence for two chemosensory pathways in Rhodobacter sphaeroides. JF - Mol Microbiol VL - 26 IS - 5 SP - 1083 EP - 1096 AD - Department of Biochemistry, Oxford University, UK. SN - 0950-382X N2 - In contrast to enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. Although a chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene, deletion of the entire chemotaxis operon had only minor effects on chemotactic behaviour under the conditions tested. Responses to sugars were enhanced in tethered cells but in all other chemotaxis assays behaviour of the operon deletion mutant was wild type. The mutant also showed wild-type responses to weak organic acids such as acetate and propionate, the dominant chemoattractants for this organism, under all conditions. This is in direct contrast to the enterics in which CheA, CheW and CheY are absolutely essential for taxis to PTS sugars, oxygen and MCP-dependent chemoeffectors. The operon deletion mutant was subjected to Tn5 transposon mutagenesis and new mutants selected using a chemotaxis and phototaxis screen. One mutant, JPA203, was non-chemotactic on swarm plates and showed inverted responses when tethered or subjected to changes in light intensity. Characterization of the Tn5 insertion in JPA203 identified a second chemotaxis operon in R. sphaeroides that contains homologues of cheY, cheA and cheR, the first homologue of cheB and two homologues of cheW. The new genes were labelled orf10, cheY(III), cheA(II) cheW(II), cheW(III), cheR(II), cheB and tlpC. When introduced into a wild-type background, deletion of cheA(II) produced a chemotaxis minus phenotype in R. sphaeroides, suggesting that cheA(II) forms part of a dominant chemotactic pathway, whereas the earlier identified operon plays only a minor role under laboratory conditions. The data presented here support the existence of two chemosensory pathways in R. sphaeroides, a feature that so far is unique in bacterial chemotaxis. KW - chemosensory KW - chemotaxis KW - pathways KW - rhodobacter KW - sphaeroides AU - Hamblin, PA AU - Maguire, BA AU - Grishanin, RN AU - Armitage, JP PY - 1997/12// UR - http://view.ncbi.nlm.nih.gov/pubmed/9426144 ER -