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J. Bacteriol., Dec 1997, 7264-7273, Vol 179, No. 23
JH Zeilstra-Ryalls, K Gabbert, NJ Mouncey, S Kaplan and RG Kranz
The fnr gene encodes a regulatory protein involved in the response to
oxygen in a variety of bacterial genera. For example, it was previously
shown that the anoxygenic, photosynthetic bacterium Rhodobacter sphaeroides
requires the fnrL gene for growth under anaerobic, photosynthetic
conditions. Additionally, the FnrL protein in R. sphaeroides is required
for anaerobic growth in the dark with an alternative electron acceptor, but
it is not essential for aerobic growth. In this study, the fnrL locus from
Rhodobacter capsulatus was cloned and sequenced. Surprisingly, an R.
capsulatus strain with the fnrL gene deleted grows like the wild type under
either photosynthetic or aerobic conditions but does not grow anaerobically
with alternative electron acceptors such as dimethyl sulfoxide (DMSO) or
trimethylamine oxide. It is demonstrated that the c-type cytochrome induced
upon anaerobic growth on DMSO is not synthesized in the R. capsulatus fnrL
mutant. In contrast to wild-type strains, R. sphaeroides and R. capsulatus
fnrL mutants do not synthesize the anaerobically, DMSO- induced reductase.
Mechanisms that explain the basis for FnrL function in both organisms are
discussed.
Copyright © 1997, American Society for Microbiology
Analysis of the fnrL gene and its function in Rhodobacter capsulatus
Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 77225, USA.
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