Metabolism is required for chemotaxis to sugars in Rhodobacter sphaeroides

Jeziore-Sassoon, Yehudit; Hamblin, Paul A.; Bootle-Wilbraham, Carolyn A.; Poole, Philip S.; Armitage, Judith P.

doi:10.1099/00221287-144-1-229

Cited by 47 publications

(37 citation statements)

References 56 publications

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“…The reason(s) for these significant differences from the E. coli model is currently unknown for either R. sphaeroides (20) or A. brasilense. In contrast to chemotaxis in E. coli, metabolism-dependent chemotaxis has been proposed as a major motility behavior for both R. sphaeroides (13) and A. brasilense (1,2,11) and may be one of the factors contributing to the observed differences.…”

Section: Discussionmentioning

confidence: 81%

Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

2006

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It has previously been reported that the alpha-proteobacterium Azospirillum brasilense undergoes methylation-independent chemotaxis; however, a recent study revealed cheB and cheR genes in this organism. We have constructed cheB, cheR, and cheBR mutants of A. brasilense and determined that the CheB and CheR proteins under study significantly influence chemotaxis and aerotaxis but are not essential for these behaviors to occur. First, we found that although cells lacking CheB, CheR, or both were no longer capable of responding to the addition of most chemoattractants in a temporal gradient assay, they did show a chemotactic response (albeit reduced) in a spatial gradient assay. Second, in comparison to the wild type, cheB and cheR mutants under steady-state conditions exhibited an altered swimming bias, whereas the cheBR mutant and the che operon mutant did not. Third, cheB and cheR mutants were null for aerotaxis, whereas the cheBR mutant showed reduced aerotaxis. In contrast to the swimming bias for the model organism Escherichia coli, the swimming bias in A. brasilense cells was dependent on the carbon source present and cells released methanol upon addition of some attractants and upon removal of other attractants. In comparison to the wild type, the cheB, cheR, and cheBR mutants showed various altered patterns of methanol release upon exposure to attractants. This study reveals a significant difference between the chemotaxis adaptation system of A. brasilense and that of the model organism E. coli and suggests that multiple chemotaxis systems are present and contribute to chemotaxis and aerotaxis in A. brasilense.

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Section: Discussionmentioning

confidence: 81%

Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

2006

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“…The final reaction mixture contained 50 mM Tris-Cl (pH 8.9), 10 mM glucose-6-phosphate, 10 mM MgCl 2 , 0.2 mM ATP, and 0.2 mM NADP ϩ . The assay was started by addition of 100 to 200 g of crude extract protein (24). GSSG reductase activity was measured by monitoring the GSSG-dependent oxidation of NADPH to NADP ϩ .…”

Section: Methodsmentioning

confidence: 99%

Link between the Membrane-Bound Pyridine Nucleotide Transhydrogenase and Glutathione-Dependent Processes in Rhodobacter sphaeroides

Hickman¹,

Barber

Skaar³

et al. 2002

J Bacteriol

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The presence of a glutathione-dependent pathway for formaldehyde oxidation in the facultative phototroph Rhodobacter sphaeroides has allowed the identification of gene products that contribute to formaldehyde metabolism. Mutants lacking the glutathione-dependent formaldehyde dehydrogenase (GSH-FDH) are sensitive to metabolic sources of formaldehyde, like methanol. This growth phenotype is correlated with a defect in formaldehyde oxidation. Additional methanol-sensitive mutants were isolated that contained Tn5 insertions in pntA, which encodes the ␣ subunit of the membrane-bound pyridine nucleotide transhydrogenase. Mutants lacking transhydrogenase activity have phenotypic and physiological characteristics that are different from those that lack GSH-FDH activity. For example, cells lacking transhydrogenase activity can utilize methanol as a sole carbon source in the absence of oxygen and do not display a formaldehyde oxidation defect, as determined by whole-cell 13 C-nuclear magnetic resonance. Since transhydrogenase can be a major source of NADPH, loss of this enzyme could result in a requirement for another source for this compound. Evidence supporting this hypothesis includes increased specific activities of other NADPH-producing enzymes and the finding that glucose utilization by the Entner-Doudoroff pathway restores aerobic methanol resistance to cells lacking transhydrogenase activity. Mutants lacking transhydrogenase activity also have higher levels of glutathione disulfide under aerobic conditions, so it is consistent that this strain has increased sensitivity to oxidative stress agents like diamide, which are known to alter the oxidation reduction state of the glutathione pool. A model will be presented to explain the role of transhydrogenase under aerobic conditions when cells need glutathione both for GSH-FDH activity and to repair oxidatively damaged proteins.

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“…Strain K60 was attracted to galactose and succinate on plates, but not in the 30-min agarose plug assay (Table 2). Chemotactic responses to certain compounds by Pseudomonas putida and Rhodobacter sphaeroides can be induced by preculturing in medium containing the substrate (22,26), so we speculate that in K60 taxis toward succinate and galactose, chemotaxis is inducible. However, we cannot exclude the possibility that the 1 mM compound concentration in the agarose plug was below a minimal detection level.…”

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confidence: 99%

Chemotaxis Is Required for Virulence and Competitive Fitness of the Bacterial Wilt Pathogen Ralstonia solanacearum

2006

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Ralstonia solanacearum, a soilborne plant pathogen of considerable economic importance, invades host plant roots from the soil. Qualitative and quantitative chemotaxis assays revealed that this bacterium is specifically attracted to diverse amino acids and organic acids, and especially to root exudates from the host plant tomato. Exudates from rice, a nonhost plant, were less attractive. Eight different strains from this heterogeneous species complex varied significantly in their attraction to a panel of carbohydrate stimuli, raising the possibility that chemotactic responses may be differentially selected traits that confer adaptation to various hosts or ecological conditions. Previous studies found that an aflagellate mutant lacking swimming motility is significantly reduced in virulence, but the role of directed motility mediated by the chemotaxis system was not known. Two site-directed R. solanacearum mutants lacking either CheA or CheW, which are core chemotaxis signal transduction proteins, were completely nonchemotactic but retained normal swimming motility. In biologically realistic soil soak virulence assays on tomato plants, both nonchemotactic mutants had significantly reduced virulence indistinguishable from that of a nonmotile mutant, demonstrating that directed motility, not simply random motion, is required for full virulence. In contrast, nontactic strains were as virulent as the wild-type strain was when bacteria were introduced directly into the plant stem through a cut petiole, indicating that taxis makes its contribution to virulence in the early stages of host invasion and colonization. When inoculated individually by soaking the soil, both nontactic mutants reached the same population sizes as the wild type did in the stems of tomato plants just beginning to wilt. However, when tomato plants were coinoculated with a 1:1 mixture of a nontactic mutant and its wild-type parent, the wild-type strain outcompeted both nontactic mutants by 100-fold. Together, these results indicate that chemotaxis is an important trait for virulence and pathogenic fitness in this plant pathogen.Ralstonia solanacearum, a soilborne gram-negative bacterium, causes bacterial wilt disease in many important crop plants, including potato, tobacco, tomato, banana, and peanut plants. The pathogen causes severe losses worldwide due to its wide geographic distribution and unusually broad host range, which spans more than 50 plant families. R. solanacearum is metabolically versatile, surviving and thriving in such diverse habitats as water, soil, and latently infected plants (23). The bacterium normally invades plant roots from the soil through wounds or natural openings, colonizes the intercellular space of the root cortex and vascular parenchyma, and eventually enters the xylem vessel and spreads up into the stem and leaves, where the pathogen cell density commonly surpasses 10 9 CFU/g of host tissue (33, 55). Affected plants suffer chlorosis, stunting, wilting, and usually die rapidly. Many factors contribute to bacterial ...

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Metabolism is required for chemotaxis to sugars in Rhodobacter sphaeroides

Cited by 47 publications

References 56 publications

Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

Link between the Membrane-Bound Pyridine Nucleotide Transhydrogenase and Glutathione-Dependent Processes in Rhodobacter sphaeroides

Chemotaxis Is Required for Virulence and Competitive Fitness of the Bacterial Wilt Pathogen Ralstonia solanacearum

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