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J Bacteriol, March 1998, p. 1248-1255, Vol. 180, No. 5
Department of Biology, Indiana University,
Bloomington, Indiana 47405
Received 12 August 1997/Accepted 18 December 1997
The purple photosynthetic bacterium Rhodospirillum
centenum is capable of forming swarm colonies that rapidly
migrate toward or away from light, depending on the wavelength of
excitation. To identify components specific for photoperception, we
conducted mini-Tn5-mediated mutagenesis and screened
approximately 23,000 transposition events for mutants that failed to
respond to either continuous illumination or to a step down in light
intensity. A majority of the ca. 250 mutants identified lost the
ability to form motile swarm cells on an agar surface. These cells
appeared to contain defects in the synthesis or assembly of
surface-induced lateral flagella. Another large fraction of mutants
that were unresponsive to light were shown to be defective in the
formation of a functional photosynthetic apparatus. Several
photosensory mutants also were obtained with defects in the perception
and transmission of light signals. Twelve mutants in this class were shown to contain disruptions in a chemotaxis operon, and five mutants
contained disruptions of components unique to photoperception. It was
shown that screening for photosensory defective R. centenum swarm colonies is an effective method for genetic dissection of the
mechanism of light sensing in eubacteria.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Isolation of Rhodospirillum centenum
Mutants Defective in Phototactic Colony Motility by Transposon
Mutagenesis
*
Corresponding author. Mailing address: Department of
Biology, Indiana University, Jordan Hall, Bloomington, IN 47405. Phone: (812) 855-6595. Fax: (812) 856-4178. E-mail:
cbauer{at}bio.indiana.edu.
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