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J. Bacteriol., 09 1997, 5720-5727, Vol 179, No. 18
ZY Jiang, H Gest and CE Bauer
The chemotaxis gene cluster from the photosynthetic bacterium
Rhodospirillum centenum contains five open reading frames (ORFs) that have
significant sequence homology to chemotaxis genes from other bacteria. To
elucidate the functions of each ORF, we have made various mutations in the
gene cluster and analyzed their phenotypic defects. Deletion of the entire
che operon (delta che), as well as nonpolar disruptions of cheAY, cheW, and
cheR, resulted in a smooth-swimming phenotype, whereas disruption of cheB
resulted in a locked tumbly phenotype. Each of these mutants was defective
in chemotactic response. Interestingly, disruption of cheY resulted in a
slight increase in the frequency of tumbling/reversal with no obvious
defects in chemotactic response. In contrast to observations with
Escherichia coli and several other bacteria, we found that all of the che
mutant cells were capable of differentiating into hyperflagellated swarmer
cells when plated on a solid agar surface. When viewed microscopically, the
smooth-swimming che mutants exhibited active surface motility but were
unable to respond to a step-down in light intensity. Both positive and
negative phototactic responses were abolished in all che mutants, including
the cheY mutant. These results indicate that eubacterial photosensory
perception is mediated by light-generated signals that are transmitted
through the chemotaxis signal transduction cascade.
Copyright © 1997, American Society for Microbiology
Chemosensory and photosensory perception in purple photosynthetic bacteria utilize common signal transduction components
Department of Biology, Indiana University, Bloomington 47405, USA.
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