scholarly journals Up-Regulated Expression of the cbbI and cbbII Operons during Photoheterotrophic Growth of a Ribulose 1,5-Bisphosphate Carboxylase-Oxygenase Deletion Mutant of Rhodobacter sphaeroides

2002 ◽  
Vol 184 (23) ◽  
pp. 6721-6724 ◽  
Author(s):  
Stephanie A. Smith ◽  
F. Robert Tabita
Keyword(s):  
Electron Donor ◽  
Rhodobacter Sphaeroides ◽  
Deletion Mutant ◽  
Transcriptional Activator ◽  
Deletion Strain ◽  
Bisphosphate Carboxylase ◽  
Regulated Expression ◽  
Photoheterotrophic Growth

ABSTRACT In a Rhodobacter sphaeroides ribulose 1,5-bisphosphate carboxylase-oxygenase deletion strain that requires an exogenous electron donor for photoheterotrophic growth, transcription of the genes of the Calvin-Benson-Bassham (CBB) cycle was increased. This finding pointed to a potential physiological effector that enhances the capability of the positive transcriptional activator CbbR to mediate cbb transcription. This effector is most likely ribulose 1,5-bisphosphate or a metabolite derived from this CBB pathway intermediate.

scholarly journals Expression of glnB and aglnB-Like Gene (glnK) in a Ribulose Bisphosphate Carboxylase/Oxygenase-Deficient Mutant of Rhodobacter sphaeroides

1998 ◽  
Vol 180 (17) ◽  
pp. 4644-4649 ◽  
Author(s):  
Yilei Qian ◽  
F. Robert Tabita
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Nitrogenase Activity ◽  
Growth Conditions ◽  
Ribulose Bisphosphate Carboxylase ◽  
Deficient Mutant ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
Negative Effect ◽  
In The Wild ◽  
Photoheterotrophic Growth

ABSTRACT In a ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO)-deficient mutant of Rhodobacter sphaeroides, strain 16PHC, nitrogenase activity was derepressed in the presence of ammonia under photoheterotrophic growth conditions. Previous studies also showed that reintroduction of a functional RubisCO and Calvin-Benson-Bassham (CBB) pathway suppressed the deregulation of nitrogenase synthesis in this strain. In this study, the derepression of nitrogenase synthesis in the presence of ammonia in strain 16PHC was further explored by using aglnB::lacZ fusion, since the product of the glnB gene is known to have a negative effect on ammonia-regulated nif control. It was found thatglnB expression was repressed in strain 16PHC under photoheterotrophic growth conditions with either ammonia or glutamate as the nitrogen source; glutamine synthetase (GS) levels were also affected in this strain. However, when cells regained a functional CBB pathway by trans complementation of the deleted genes, wild-type levels of GS and glnB expression were restored. Furthermore, a glnB-like gene,glnK, was isolated from this organism, and its expression was found to be under tight nitrogen control in the wild type. Surprisingly, glnK expression was found to be derepressed in strain 16PHC under photoheterotrophic conditions in the presence of ammonia.

scholarly journals Differential Expression of the CO2 Fixation Operons of Rhodobacter sphaeroides by the Prr/Reg Two-Component System during Chemoautotrophic Growth

2002 ◽  
Vol 184 (23) ◽  
pp. 6654-6664 ◽  
Author(s):  
Janet L. Gibson ◽  
James M. Dubbs ◽  
F. Robert Tabita
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Cytochrome Oxidase ◽  
Rhodobacter Sphaeroides ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Signal Transduction Pathway ◽  
Pentose Phosphate ◽  
Bisphosphate Carboxylase

ABSTRACT In Rhodobacter sphaeroides, the two cbb operons encoding duplicated Calvin-Benson Bassham (CBB) CO2 fixation reductive pentose phosphate cycle structural genes are differentially controlled. In attempts to define the molecular basis for the differential regulation, the effects of mutations in genes encoding a subunit of Cbb3 cytochrome oxidase, ccoP, and a global response regulator, prrA (regA), were characterized with respect to CO2 fixation (cbb) gene expression by using translational lac fusions to the R. sphaeroides cbb I and cbbII promoters. Inactivation of the ccoP gene resulted in derepression of both promoters during chemoheterotophic growth, where cbb expression is normally repressed; expression was also enhanced over normal levels during phototrophic growth. The prrA mutation effected reduced expression of cbbI and cbbII promoters during chemoheterotrophic growth, whereas intermediate levels of expression were observed in a double ccoP prrA mutant. PrrA and ccoP1 prrA strains cannot grow phototrophically, so it is impossible to examine cbb expression in these backgrounds under this growth mode. In this study, however, we found that PrrA mutants of R. sphaeroides were capable of chemoautotrophic growth, allowing, for the first time, an opportunity to directly examine the requirement of PrrA for cbb gene expression in vivo under growth conditions where the CBB cycle and CO2 fixation are required. Expression from the cbbII promoter was severely reduced in the PrrA mutants during chemoautotrophic growth, whereas cbbI expression was either unaffected or enhanced. Mutations in ccoQ had no effect on expression from either promoter. These observations suggest that the Prr signal transduction pathway is not always directly linked to Cbb3 cytochrome oxidase activity, at least with respect to cbb gene expression. In addition, lac fusions containing various lengths of the cbbI promoter demonstrated distinct sequences involved in positive regulation during photoautotrophic versus chemoautotrophic growth, suggesting that different regulatory proteins may be involved. In Rhodobacter capsulatus, ribulose 1,5-bisphosphate carboxylase-oxygenase (RubisCO) expression was not affected by cco mutations during photoheterotrophic growth, suggesting that differences exist in signal transduction pathways regulating cbb genes in the related organisms.

scholarly journals Deletion of the 389 N-Terminal Residues of the Transcriptional Activator AREA Does Not Result in Nitrogen Metabolite Derepression in Aspergillus nidulans

1998 ◽  
Vol 180 (21) ◽  
pp. 5762-5764 ◽  
Author(s):  
Mark X. Caddick ◽  
Herbert N. Arst
Keyword(s):  
Amino Acids ◽  
Aspergillus Nidulans ◽  
Deletion Mutant ◽  
Transcriptional Activator ◽  
Gene Replacement ◽  
Untranslated Regions ◽  
Homologous Gene ◽  
Heterologous Promoter ◽  
Native Promoter ◽  
N Terminus

ABSTRACT Utilizing a homologous gene replacement in order to retain the native promoter and 5′ and 3′ untranslated messenger regions (and thereby ensure physiological validity), we have shown that deletion of the N-terminal 389 amino acids of the transcriptional activator AREA does not result in nitrogen metabolite derepression inAspergillus nidulans. Our results provide no evidence for a modulating interaction involving the N terminus of AREA and contrast with those of H. K. Lamb, A. L. Dodds, D. R. Swatman, E. Cairns, and A. R. Hawkins (J. Bacteriol. 179:6649–6656, 1997), who used nontargeted ectopic copies of a construct containing a heterologous promoter and untranslated regions. Results obtained with this deletion mutant, nevertheless, provide further evidence for the dispensability of large portions of AREA.

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