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Journal of Bacteriology, July 2009, p. 4243-4250, Vol. 191, No. 13
0021-9193/09/$08.00+0 doi:10.1128/JB.01795-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Differential Accumulation of Form I RubisCO in Rhodopseudomonas palustris CGA010 under Photoheterotrophic Growth Conditions with Reduced Carbon Sources
Gauri S. Joshi,1
Simona Romagnoli,1,
Nathan C. VerBerkmoes,2
Robert L. Hettich,2
Dale Pelletier,2 and
F. Robert Tabita1,3*
Department of Microbiology, The Ohio State University, Columbus, Ohio 43210-1292,1 Biosciences and Chemical Science Divisions, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831,2 Plant Molecular Biology/Biotechnology Program, The Ohio State University, Columbus, Ohio3
Received 22 December 2008/ Accepted 7 April 2009
Rhodopseudomonas palustris is unique among characterized nonsulfur purple bacteria because of its capacity for anaerobic photoheterotrophic growth using aromatic acids. Like growth with other reduced electron donors, this growth typically requires the presence of bicarbonate/CO2 or some other added electron acceptor in the growth medium. Proteomic studies indicated that there was specific accumulation of form I ribulose 1, 5-bisphosphate carboxylase/oxygenase (RubisCO) subunit proteins (CbbL and CbbS), as well as the CbbX protein, in cells grown on benzoate without added bicarbonate; such cells used the small amounts of dissolved CO2 in the medium to support growth. These proteins were not observed in extracts from cells grown in the presence of high levels (10 mM) of added bicarbonate. To confirm the results of the proteomics studies, it was shown that the total RubisCO activity levels were significantly higher (five- to sevenfold higher) in wild-type (CGA010) cells grown on benzoate with a low level (0.5 mM) of added bicarbonate. Immunoblots indicated that the increase in RubisCO activity levels was due to a specific increase in the amount of form I RubisCO (CbbLS) and not in the amount of form II RubisCO (CbbM), which was constitutively expressed. Deletion of the main transcriptional regulator gene, cbbR, resulted in impaired growth on benzoate-containing low-bicarbonate media, and it was established that form I RubisCO synthesis was absolutely and specifically dependent on CbbR. To understand the regulatory role of the CbbRRS two-component system, strains with nonpolar deletions of the cbbRRS genes were grown on benzoate. Distinct from the results obtained with photoautotrophic growth conditions, the results of studies with various CbbRRS mutant strains indicated that this two-component system did not affect the observed enhanced synthesis of form I RubisCO under benzoate growth conditions. These studies indicate that diverse growth conditions differentially affect the ability of the CbbRRS two-component system to influence cbb transcription.
* Corresponding author. Mailing address: Department of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio 43210-1292. Phone: (614) 292-4297. Fax: (614) 292-6337. E-mail: Tabita.1{at}osu.edu
Published ahead of print on 17 April 2009.
Present address: Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy.
Journal of Bacteriology, July 2009, p. 4243-4250, Vol. 191, No. 13
0021-9193/09/$08.00+0 doi:10.1128/JB.01795-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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