Requirement of the cheB function for sensory adaptation in Escherichia coli

SummaryIn 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.

Section: Introductionmentioning

confidence: 99%

Evidence for two chemosensory pathways in Rhodobacter sphaeroides

Hamblin

Maguire

Grishanin

et al. 1997

“…However, for E. coli, negative stimuli cause increased methanol production while positive stimuli suppress methanol production (Toews et al, 1979;Kehry et al, 1984). Second, in B. subtilis, cheB or cheR null mutants exhibit partial adaptation to some attractant stimuli (Kirsch et al, 1993a,b) whereas, in E. coli, cheB or cheR null mutants do not adapt to stimuli (Parkinson and Revello, 1978;Goy et al, 1978;Yonekawa et al, 1983;Weis et al, 1990). Third, for B. subtilis, recent studies on McpB indicate that both positive and negative stimuli induce transient net demethylation events on the receptor (J. R. Kirby and G. W. Ordal, submitted).…”

Section: Introductionmentioning

confidence: 99%

Methanol production during chemotaxis to amino acids in Bacillus subtilis

Kirby

Kristich

Feinberg

et al. 1997

SummaryThe 20 common amino acids act as attractants during chemotaxis by the Gram-positive organism Bacillus subtilis. In this study, we report that all amino acids induce B. subtilis to produce methanol both upon addition and removal of the chemoeffector. Asparagine-induced methanol production is specific to the McpB receptor and aspartate-induced methanol production correlates with receptor occupancy. These findings suggest that addition and removal of all amino acids cause demethylation of specific receptors which results in methanol production. We also demonstrate that certain attractants cause greater production of methanol after multiple stimulations. CheC and CheD, while affecting the levels of receptor methylation, are not absolutely required for either methylation or demethylation. In contrast, CheY is necessary for methanol formation upon removal of attractant but not upon addition of attractant. We conclude that methanol formation due to negative stimuli indicates the existence of a unique adaptational mechanism in B. subtilis involving the response regulator, CheY.

“…Recent data, however, suggest that the oligomerization of CheZ may also provide a second adaptive mechanism (Blat and Eisenbach, 1996a;Blat and Eisenbach, 1996b). CheB, a methylesterase, and CheR, a methyltransferase, reversibly methylate the transmembrane MCPs, modulating their activity and allowing adaptive responses to chemotactic stimuli (Yonekawa et al, 1983;Stock et al, 1985). The activity of CheR is constitutive, whilst CheB is activated by phosphorylation of its N-terminal domain by CheA-phosphate (Lupas and Stock, 1989).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the chemotaxis protein CheW from Rhodobacter sphaeroides and its effect on the behaviour of Escherichia coli

Hamblin

Bourne

Armitage

1997

SummaryIn contrast to the situation in enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. A chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene. However, mutations in these genes have only minor effects on chemotaxis. In enteric species, CheW transmits sensory information from the chemoreceptors to the histidine protein kinase, CheA. Expression of R. sphaeroides cheW in Escherichia coli showed concentrationdependent inhibition of wild-type behaviour, increasing counter-clockwise rotation and thus smooth swimming -a phenotype also seen when E. coli cheW is overexpressed in E. coli. In contrast, overexpression of R. sphaeroides cheW in wild-type R. sphaeroides inhibited motility completely, the equivalent of inducing tumbly motility in E. coli. Expression of R. sphaeroides cheW in an E. coli ⌬cheW chemotaxis mutant complemented this mutation, confirming that CheW is involved in chemosensory signal transduction. However, unlike E. coli ⌬cheW mutants, inframe deletion of R. sphaeroides cheW did not affect either swimming behaviour or chemotaxis to weak organic acids, although the responses to sugars were enhanced. Therefore, although CheW may act as a signal-transduction protein in R. sphaeroides, it may have an unusual role in controlling the rotation of the flagellar motor. Furthermore, the ability of a ⌬cheW mutant to swim normally and show wild-type responses to weak acids supports the existence of additional chemosensory signal-transduction pathways.