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| The EMBO Journal
(2000) 19, 4601–4613, doi:10.1093/emboj/19.17.4601 |
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| Fine tuning bacterial chemotaxis: analysis of Rhodobacter sphaeroides behaviour under aerobic and anaerobic conditions by mutation of the major chemotaxis operons and cheY genes |
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| Deepan S.H. Shah1, Steven L. Porter1, Angela C. Martin1, Paul A. Hamblin2 and Judith P. Armitage1 |
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1 Microbiology Unit, Department of Biochemistry, The University of Oxford, South Parks Road, Oxford OX1 3QU, UK 2 Present address: Immunopathology Unit, Glaxo Wellcome Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, UK To whom correspondence should be addressed Judith P. Armitage, armitage@bioch.ox.ac.uk Received 5 April 2000; Revised 17 July 2000; Accepted 17 July 2000. |
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| Abstract |
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| Rhodobacter sphaeroides chemotaxis is significantly more complex than that of enteric bacteria. Rhodobacter sphaeroides has multiple copies of chemotaxis genes (two cheA, one cheB, two cheR, three cheW, five cheY but no cheZ), controlling a single 'stop–start' flagellum. The growth environment controls the level of expression of different groups of genes. Tethered cell analysis of mutants suggests that CheY4 and CheY5 are the motor-binding response regulators. The histidine protein kinase CheA2 mediates an attractant ('normal') response via CheY4, while CheA1 and CheY5 appear to mediate a repellent ('inverted') response. CheY3 facilitates signal termination, possibly acting as a phosphate sink, although CheY1 and CheY2 can substitute. The normal and inverted responses may be initiated by separate sets of chemoreceptors with their relative strength dependent on growth conditions. Rhodobacter sphaeroides may use antagonistic responses through two chemosensory pathways, expressed at different levels in different environments, to maintain their position in a currently optimum environment. Complex chemotaxis systems are increasingly being identified and the strategy adopted by R.sphaeroides may be common in the bacterial kingdom. |
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| Keywords: chemotaxis, cheY, flagellar motility, Rhodobacter (sphaeroides), signal transduction |
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