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Journal of Bacteriology, August 1998, p. 4258-4269, Vol. 180, No. 16
Department of Microbiology and Plant
Molecular Biology/Biotechnology Program, The Ohio State University,
Columbus, Ohio 43210-1292
Received 8 January 1998/Accepted 3 June 1998
The genes encoding enzymes of the Calvin-Benson-Bassham (CBB)
reductive pentose phosphate pathway in Rhodobacter
capsulatus are organized in at least two operons, each preceded
by a separate cbbR gene, encoding potential LysR-type
transcriptional activators. As a prelude to studies of
cbb gene regulation in R. capsulatus, the
nucleotide sequence of a 4,537-bp region, which included
cbbRII, was determined. This region
contained the following open reading frames: a partial pgm
gene (encoding phosphoglucomutase) and a complete qor
gene (encoding NADPH:quinone oxidoreductase), followed by cbbRII, cbbF (encoding
fructose 1,6-bisphosphatase), cbbP (encoding phosphoribulokinase), and part of cbbT (encoding
transketolase). Physiological control of the CBB pathway and regulation
of the R. capsulatus cbb genes were studied by using a
combination of mutant strains and promoter fusion constructs.
Characterization of mutant strains revealed that either form I or
form II ribulose 1,5-bisphosphate carboxylase/oxygenase
(RubisCO), encoded by the cbbLS and
cbbM genes, respectively, could support
photoheterotrophic and autotrophic growth. A strain with disruptions in
both cbbL and cbbM could not grow
autotrophically and grew photoheterotrophically only when dimethyl
sulfoxide was added to the culture medium. Disruption of
cbbP resulted in a strain that did not synthesize form
II RubisCO and had a phenotype similar to that observed in the
RubisCO-minus strain, suggesting that there is only one
cbbP gene in R. capsulatus and that this
gene is cotranscribed with cbbM. Analysis of RubisCO
activity and synthesis in strains with disruptions in either
cbbRI or
cbbRII, and
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Physiological Control and Regulation of the
Rhodobacter capsulatus cbb Operons

-galactosidase
determinations from wild-type and mutant strains
containing cbbIp- and
cbbIIp-lacZ fusion constructs,
indicated that the cbbI and
cbbII operons of R. capsulatus are within separate CbbR regulons.
*
Corresponding author. Mailing address: Department of
Microbiology and Plant Molecular Biology/Biotechnology Program, The
Ohio State University, 484 West 12th Ave., Columbus, OH
43210-1292. Phone: (614) 292-4297. Fax: (614) 292-6337. E-mail:
Tabita.1{at}osu.edu.
Present address: Air Force Research Laboratory/MLQR, Tyndall Air
Force Base, FL 32403-5323.
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