Genes and pathways for CO2 fixation in the obligate, chemolithoautotrophic acidophile, Acidithiobacillus ferrooxidans, Carbon fixation in A. ferrooxidans

Medientyp: E-Artikel
Titel: Genes and pathways for CO2 fixation in the obligate, chemolithoautotrophic acidophile, Acidithiobacillus ferrooxidans, Carbon fixation in A. ferrooxidans
Beteiligte: Esparza, Mario; Cárdenas, Juan Pablo; Bowien, Botho; Jedlicki, Eugenia; Holmes, David S
Erschienen: Springer Science and Business Media LLC, 2010
Erschienen in: BMC Microbiology
Sprache: Englisch
DOI: 10.1186/1471-2180-10-229
ISSN: 1471-2180
Entstehung:
Anmerkungen:
Beschreibung: <jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p> <jats:italic>Acidithiobacillus ferrooxidans</jats:italic> is chemolithoautotrophic γ-proteobacterium that thrives at extremely low pH (pH 1-2). Although a substantial amount of information is available regarding CO<jats:sub>2</jats:sub> uptake and fixation in a variety of facultative autotrophs, less is known about the processes in obligate autotrophs, especially those living in extremely acidic conditions, prompting the present study.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Four gene clusters (termed <jats:italic>cbb1-4</jats:italic>) in the <jats:italic>A. ferrooxidans</jats:italic> genome are predicted to encode enzymes and structural proteins involved in carbon assimilation via the Calvin-Benson-Bassham (CBB) cycle including form I of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO, EC 4.1.1.39) and the CO<jats:sub>2</jats:sub>-concentrating carboxysomes. RT-PCR experiments demonstrated that each gene cluster is a single transcriptional unit and thus is an operon. Operon <jats:italic>cbb1</jats:italic> is divergently transcribed from a gene, <jats:italic>cbbR</jats:italic>, encoding the LysR-type transcriptional regulator CbbR that has been shown in many organisms to regulate the expression of RubisCO genes. Sigma<jats:sup>70</jats:sup>-like -10 and -35 promoter boxes and potential CbbR-binding sites (T-N<jats:sub>11</jats:sub>-A/TNA-N<jats:sub>7</jats:sub>TNA) were predicted in the upstream regions of the four operons. Electrophoretic mobility shift assays (EMSAs) confirmed that purified CbbR is able to bind to the upstream regions of the <jats:italic>cbb1</jats:italic>, <jats:italic>cbb2</jats:italic> and <jats:italic>cbb3</jats:italic> operons, demonstrating that the predicted CbbR-binding sites are functional <jats:italic>in vitro</jats:italic>. However, CbbR failed to bind the upstream region of the <jats:italic>cbb4</jats:italic> operon that contains <jats:italic>cbbP</jats:italic>, encoding phosphoribulokinase (EC 2.7.1.19). Thus, other factors not present in the assay may be required for binding or the region lacks a functional CbbR-binding site. The <jats:italic>cbb3</jats:italic> operon contains genes predicted to encode anthranilate synthase components I and II, catalyzing the formation of anthranilate and pyruvate from chorismate. This suggests a novel regulatory connection between CO<jats:sub>2</jats:sub> fixation and tryptophan biosynthesis. The presence of a form II RubisCO could promote the ability of <jats:italic>A. ferrooxidans</jats:italic> to fix CO<jats:sub>2</jats:sub> at different concentrations of CO<jats:sub>2</jats:sub>.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p> <jats:italic>A. ferrooxidans</jats:italic> has features of <jats:italic>cbb</jats:italic> gene organization for CO<jats:sub>2</jats:sub>-assimilating functions that are characteristic of obligate chemolithoautotrophs and distinguish this group from facultative autotrophs. The most conspicuous difference is a separate operon for the <jats:italic>cbbP</jats:italic> gene. It is hypothesized that this organization may provide greater flexibility in the regulation of expression of genes involved in inorganic carbon assimilation.</jats:p> </jats:sec>
Zugangsstatus: Freier Zugang

Nur in Feld suchen:

Zuletzt gesuchte Begriffe: