Dataset Information

CO2-responsive expression and gene organization of three ribulose-1,5-bisphosphate carboxylase/oxygenase enzymes and carboxysomes in Hydrogenovibrio marinus strain MH-110.

ABSTRACT: Hydrogenovibrio marinus strain MH-110, an obligately lithoautotrophic hydrogen-oxidizing bacterium, fixes CO2 by the Calvin-Benson-Bassham cycle. Strain MH-110 possesses three different sets of genes for ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO): CbbLS-1 and CbbLS-2, which belong to form I (L8S8), and CbbM, which belongs to form II (Lx). In this paper, we report that the genes for CbbLS-1 (cbbLS-1) and CbbM (cbbM) are both followed by the cbbQO genes and preceded by the cbbR genes encoding LysR-type regulators. In contrast, the gene for CbbLS-2 (cbbLS-2) is followed by genes encoding carboxysome shell peptides. We also characterized the three RubisCOs in vivo by examining their expression profiles in environments with different CO2 availabilities. Immunoblot analyses revealed that when strain MH-110 was cultivated in 15% CO2, only the form II RubisCO, CbbM, was expressed. When strain MH-110 was cultivated in 2% CO2, CbbLS-1 was expressed in addition to CbbM. In the 0.15% CO2 culture, the expression of CbbM decreased and that of CbbLS-1 disappeared, and CbbLS-2 was expressed. In the atmospheric CO2 concentration of approximately 0.03%, all three RubisCOs were expressed. Transcriptional analyses of mRNA by reverse transcription-PCR showed that the regulation was at the transcriptional level. Electron microscopic observation of MH-110 cells revealed the formation of carboxysomes in the 0.15% CO2 concentration. The results obtained here indicate that strain MH-110 adapts well to various CO2 concentrations by using different types of RubisCO enzymes.

SUBMITTER: Yoshizawa Y

PROVIDER: S-EPMC516815 | biostudies-literature | 2004 Sep

REPOSITORIES: biostudies-literature

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CO2-responsive expression and gene organization of three ribulose-1,5-bisphosphate carboxylase/oxygenase enzymes and carboxysomes in Hydrogenovibrio marinus strain MH-110.

Yoshizawa Yoichi Y Toyoda Koichi K Arai Hiroyuki H Ishii Masaharu M Igarashi Yasuo Y

Journal of bacteriology 20040901 17

Hydrogenovibrio marinus strain MH-110, an obligately lithoautotrophic hydrogen-oxidizing bacterium, fixes CO2 by the Calvin-Benson-Bassham cycle. Strain MH-110 possesses three different sets of genes for ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO): CbbLS-1 and CbbLS-2, which belong to form I (L8S8), and CbbM, which belongs to form II (Lx). In this paper, we report that the genes for CbbLS-1 (cbbLS-1) and CbbM (cbbM) are both followed by the cbbQO genes and preceded by the cbbR gene ...[more]

PMID: 15317772

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Project description:The ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) enzyme found in plants, algae, and an array of autotrophic bacteria is also encoded by a subset of methanotrophs, but its role in these microbes has largely remained elusive. In this study, we showed that CO2 was requisite for RubisCO-encoding Methylococcus capsulatus strain Bath growth in a bioreactor with continuous influent and effluent gas flow. RNA sequencing identified active transcription of several carboxylating enzymes, including key enzymes of the Calvin and serine cycles, that could mediate CO2 assimilation during cultivation with both CH4 and CO2 as carbon sources. Marker exchange mutagenesis of M. capsulatus Bath genes encoding key enzymes of potential CO2-assimilating metabolic pathways indicated that a complete serine cycle is not required, whereas RubisCO is essential for growth of this bacterium. 13CO2 tracer analysis showed that CH4 and CO2 enter overlapping anaplerotic pathways and implicated RubisCO as the primary enzyme mediating CO2 assimilation in M. capsulatus Bath. Notably, we quantified the relative abundance of 3-phosphoglycerate and ribulose-1,5-bisphosphate 13C isotopes, which supported that RubisCO-produced 3-phosphoglycerate is primarily converted to ribulose-1-5-bisphosphate via the oxidative pentose phosphate pathway in M. capsulatus Bath. Collectively, our data establish that RubisCO and CO2 play essential roles in M. capsulatus Bath metabolism. This study expands the known capacity of methanotrophs to fix CO2 via RubisCO, which may play a more pivotal role in the Earth's biogeochemical carbon cycling and greenhouse gas regulation than previously recognized. Further, M. capsulatus Bath and other CO2-assimilating methanotrophs represent excellent candidates for use in the bioconversion of biogas waste streams that consist of both CH4 and CO2. IMPORTANCE The importance of RubisCO and CO2 in M. capsulatus Bath metabolism is unclear. In this study, we demonstrated that both CO2 and RubisCO are essential for M. capsulatus Bath growth. 13CO2 tracing experiments supported that RubisCO mediates CO2 fixation and that a noncanonical Calvin cycle is active in this organism. Our study provides insights into the expanding knowledge of methanotroph metabolism and implicates dually CH4/CO2-utilizing bacteria as more important players in the biogeochemical carbon cycle than previously appreciated. In addition, M. capsulatus and other methanotrophs with CO2 assimilation capacity represent candidate organisms for the development of biotechnologies to mitigate the two most abundant greenhouse gases, CH4 and CO2.

Dataset Information

CO2-responsive expression and gene organization of three ribulose-1,5-bisphosphate carboxylase/oxygenase enzymes and carboxysomes in Hydrogenovibrio marinus strain MH-110.

Publications

CO2-responsive expression and gene organization of three ribulose-1,5-bisphosphate carboxylase/oxygenase enzymes and carboxysomes in Hydrogenovibrio marinus strain MH-110.

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