SOMETHING FROM ALMOST NOTHING: Carbon Dioxide Fixation in Chemoautotrophs

Abstract

The last decade has seen significant advances in our understanding of the physiology, ecology, and molecular biology of chemoautotrophic bacteria. Many ecosystems are dependent on CO2 fixation by either free-living or symbiotic chemoautotrophs. CO2 fixation in the chemoautotroph occurs via the Calvin-Benson-Bassham cycle. The cycle is characterized by three unique enzymatic activities: ribulose bisphosphate carboxylase/oxygenase, phosphoribulokinase, and sedoheptulose bisphosphatase. Ribulose bisphosphate carboxylase/oxygenase is commonly found in the cytoplasm, but a number of bacteria package much of the enzyme into polyhedral organelles, the carboxysomes. The carboxysome genes are located adjacent to cbb genes, which are often, but not always, clustered in large operons. The availability of carbon and reduced substrates control the expression of cbb genes in concert with the LysR-type transcriptional regulator, CbbR. Additional regulatory proteins may also be involved. All of these, as well as related topics, are discussed in detail in this review.

Protein Content of Polyhedral Organelles Involved in Coenzyme B 12 -Dependent Degradation of 1,2-Propanediol in Salmonella enterica Serovar Typhimurium LT2

“…This raises two interesting questions: how many different metabolic processes occur within protein-bound organelles and how widely distributed are such organelles in nature? Electron microscopy has shown that carboxysomes are produced by a number of photo-and chemoautotrophic bacteria (11,12,33 ). In addition, based on bioinformatic studies it appears that Desulfitobacterium hafniense and Desulfovibrio desulfuricans also have the potential to produce a polyhedral organelle.…”

“…However, carboxysomes and the S. enterica organelles differ in a number of ways. Carboxysomes function to enhance autotrophic growth at low CO 2 concentrations (2,21,25,33), and the carboxysomes of Halothiobacillus neapolitanus (which are the best studied) consist of a protein shell composed of at …”

“…However, carboxysomes and the S. enterica organelles differ in a number of ways. Carboxysomes function to enhance autotrophic growth at low CO 2 concentrations (2,21,25,33), and the carboxysomes of Halothiobacillus neapolitanus (which are the best studied) consist of a protein shell composed of at least six different proteins which encases most of the cell's ribulose 1,5-bisphosphate carboxylase-oxygenase (RuBisCO) (3,4,14,16,18). In contrast, the organelles of S. enterica do not contain RuBisCO but instead consist of Ado-B 12 -dependent diol dehydratase and a protein shell composed of the PduA protein as well as other unidentified proteins (9,17).…”

Genetic diversity of inorganic carbon uptake systems causes variation in CO2 response of the cyanobacterium Microcystis

“…Possible LysR transcriptional regulator binding sites were defined as TNA-N 7/8 -TNA (Shively et al, 1998;Woodger et al, 2007;Nishimura et al, 2008). The most likely À 10 transcriptional start site was based on Synechocystis PCC 6803 data, most commonly 5 0 -TAAAAT-3 0 (Mitschke et al, 2011).…”

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“…Molecular oxygen is often depleted within the upper few millimeters of the sediments (Sweerts et al 1989), creating a steep chemical gradient that provides a microenvironment with high chemoautotrophic potential (Shively et al 1998). Processes of ammonium, sulfur, and methane oxidation are examples of some redox reactions associated with chemosynthesis in lake sediments (EnrichPrast et al 2009).…”