Physiological Control and Regulation of the Rhodobacter capsulatus cbb Operons

Abstract

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 ofcbb gene regulation in R. capsulatus, the nucleotide sequence of a 4,537-bp region, which includedcbbR II, was determined. This region contained the following open reading frames: a partial pgmgene (encoding phosphoglucomutase) and a complete qorgene (encoding NADPH:quinone oxidoreductase), followed by cbbR II, 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 andcbbM 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 ofcbbP 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 onecbbP gene in R. capsulatus and that this gene is cotranscribed with cbbM. Analysis of RubisCO activity and synthesis in strains with disruptions in eithercbbR I orcbbR II, and β-galactosidase determinations from wild-type and mutant strains containing cbb Ip- andcbb IIp-lacZ fusion constructs, indicated that the cbb I andcbb II operons of R. capsulatus are within separate CbbR regulons.

Development of a solar-powered microbial fuel cell

“…1988), including polyhydroxybutyrate synthesis (which can account for up to 60% of the cellular dry weight), the Calvin cycle [assimilating carbon dioxide even if other carbon sources are present (Richaud et al. 1991; Paoli et al. 1998; Tichi and Tabita 2001)], hydrogen evolution (Gest and Kamen 1949), reduction of other electron acceptors (McEwan et al.…”

Residues that influence in vivo and in vitro CbbR function in Rhodobacter sphaeroides and identification of a specific region critical for co‐inducer recognition

“…Rhodobacter capsulatus also has two cbb operons (cbb I and cbb II ) and two cbbR genes (cbbR I and cbbR II , encoding CbbR I and CbbR II respectively) associated with each cbb operon (Paoli et al, 1998). R. sphaeroides CbbR is much more similar to CbbR II from R. capsulatus than to CbbR I (Paoli et al, 1998;Vichivanives et al, 2000).…”

Unravelling the regulatory twist – regulation of CO2 fixation in Rhodopseudomonas palustris CGA010 mediated by atypical response regulator(s)†

“…palustris, while in Rb. capsulatus there are two CbbR proteins (CbbRI and CbbRII), each regulating its cognate operon (Paoli et al, 1998;Vichivanives et al, 2000). The unique CbbRRS system regulates the expression of the cbbI CO2 fixation genes in Rps.…”