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The article presents a study which examines the transcriptome response of Rhodobacter sphaeroides 2.4.1 to nitrosative stress. The study performs microarray experiment, Genechip data analysis, and RNA extraction to determine the physiological response of R. sphaeroides to S-nitrosoglutathione (GSNO) and sodium nitroprusside (SNP). Results show that GSNO and SNP can affect the expression of different genes.

The consensus DNA binding sequence for PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, is poorly defined. We have performed mutational analysis of PrrA site 2, of the RSP3361 gene, to which PrrA binds in vitro (J. M. Eraso and S. Kaplan, J. Bacteriol. 191:4341-4352, 2009), to further define the consensus sequence for DNA binding. Two half-sites of equal length, containing 6 nucleotides each, were required for PrrA binding to this DNA sequence. Systematic nucleotide substitutions in both inverted half-sites led to a decrease in binding affinity of phosphorylated PrrA in vitro, the level of which was dependent on the substitution. The reduced binding affinities were confirmed by competition experiments and led to proportional decreases in the expression of lacZ transcriptional fusions to the RSP3361 gene in vivo. The 5-nucleotide spacer region between the half-sites was found to be optimal for PrrA binding to the wild-type half-sites, as shown by decreased PrrA DNA binding affinities to synthetic DNA sequences without spacer regions or with spacer regions ranging from 1 to 10 nucleotides. The synthetic spacer region alleles also showed decreased gene expression in vivo when analyzed using lacZ transcriptional fusions. We have studied three additional DNA sequences to which PrrA binds in vitro. They are located in the regulatory regions of genes positively regulated by PrrA and contain spacer regions with 5 or 8 nucleotides. We demonstrate that PrrA can bind in vitro to DNA sequences with different lengths in the spacer regions between the half-sites. [ABSTRACT FROM AUTHOR]

In the present study, we show in vitro binding of PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, to the PrrA site 2, within the RSP3361 locus. Specific binding, as shown by competition experiments, requires the phosphorylation of PrrA. The binding affinity of PrrA for site 2 was found to increase 4- to 10-fold when spermidine was added to the binding reaction. The presence of extracellular concentrations of spermidine in growing cultures of R. sphaeroides gave rise to a twofold increase in the expression of the photosynthesis genes pucB and pufB, as well as the RSP3361 gene, under aerobic growth conditions, as shown by the use of lacZ transcriptional fusions, and led to the production of light-harvesting spectral complexes. In addition, we show that negative supercoiling positively regulates the expression of the RSP3361 gene, as well as pucB. We show the importance of supercoiling through an evaluation of the regulation of gene expression in situ by supercoiling, in the case of the former gene, as well as using the DNA gyrase inhibitor novobiocin. We propose that polyamines and DNA supercoiling act synergistically to regulate expression of the RSP3361 gene, partly by affecting the affinity of PrrA binding to the PrrA site 2 within the RSP3361 gene. [ABSTRACT FROM AUTHOR]

The volume of electron flow through the cbb3 branch of the electron transport chain and the redox state of the quinone pool generate signals that regulate photosynthesis gene expression in Rhodobacter sphaeroides. An inhibitory signal is generated at the level of the catalytic subunit of the cbb3 cytochrome c oxidase and is transduced through the membrane-localized PrrC polypeptide to the PrrBA two-component activation system, which controls the expression of most of the photosynthesis genes in response to O2. The redox state of the quinone pool is monitored by the redox-active AppA antirepressor protein, which determines the functional state of the PpsR repressor protein. The antirepressor/repressor system as well as a modulator of AppA function, TspO, together with FnrL and PrrA stringently control photopigment gene expression. These regulatory elements, together with spectral complex-specific assembly factors, control the ultimate cellular levels and composition of the photosynthetic membrane. [ABSTRACT FROM AUTHOR]

Here we show that the extent of electron flow through the cbb3 oxidase of Rhodobacter sphaeroides is inversely related to the expression levels of those photosynthesis genes that are under control of the PrrBA two-component activation system: the greater the electron flow, the stronger the inhibitory signal generated by the cbb3 oxidase to repress photosynthesis gene expression. Using site-directed mutagenesis, we show that intramolecular electron transfer within the cbb3 oxidase is involved in signal generation and transduction and this signal does not directly involve the intervention of molecular oxygen. In addition to the cbb3 oxidase, the redox state of the quinone pool controls the transcription rate of the puc opecon via the AppA-PpsR untirepressor-repressor system. Together, these interacting regulatory circuits are depicted in a model that permits us to understand the regulation by oxygen and light of photosynthesis gene expression in R.sphaeroides. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the role of the cbb... terminal cytochrome c oxidase of Rhodobacter sphaeroides and the cognate ccoNOQP operon in the oxygen regulation of photosynthesis gene expression. Materials and methods; Results and discussion.

Examines the regulation of dimethyl sulfoxide reductase (dor) gene expression in Rhodobacter sphaeroides 2.4.1. Description of the Rhodobacter sphaeroides 2.4.1; Capacity of expression of the dorS and dorR genes; Information on the roles of DorS and DorR proteins.

Presents a study which investigated the role of the fnrL gene in photosystem gene expression and photosynthetic growth of Rhodobacter sphaeroides 2.4.1. Details on factors mediating oxygen control of photosynthesis gene expression in Rhodobacter sphaeroides; Research methods employed in this study; Analysis of statistical data.

Investigates evidence for the role of redox carriers in the expression of photosynthesis genes and of carotenoid biosynthesis in Rhodobacter sphaeroides 2.4.1. Metabolic versatility of R. sphaeroides; Determination of gene role in the photosynthetic apparatus and in carotenoid accumulation; Proposal regarding rdxB or ccoP gene mutations. biogenesis.

Presents a study which aimed to examine the role and site of action of AppA in the regulatory network governing photosynthesis gene expression. Relationship between AppA and other regulators of photosynthesis gene expression; Necessity of AppA for development of the photosynthetic apparatus in a ppsR null background.

Examines the characterization of the Rhodobacter sphaeroides 2.4.1 rho gene. Genetic analysis of the function, expression and structure of gene; Materials and techniques used in experiments carried out; Results of study; References.

Reports on the cloning and sequencing of the photosynthesis response regulatory (PRR) region from the wild-type and the trans-acting, oxygen-insensitive mutant T1a in Rhodobacter sphaeroides. Synthesis of the specialized intracytoplasmic membrane; Measurements of mRNA levels in cells containing the prrB78 mutation; Genetic organization of the PRR region.

Describes the genetic transcription and expression of the puf operon in Rhodobacter sphaeroides 2.4.1. Speculation on existence of a 20-codon open reading frame designated as pufK; Effect of presence of rare codons on level of pufK translation; Translational efficiency of pufK; Phenotype analysis of pufK mutations.

The puf operon of the purple nonsulfur photosynthetic bacterium, Rhodobacter sphaeroides, contains structural gene information for at least two functionally distinct bacteriochlorophyll-protein complexes (light harvesting and reaction center) which are present in a fixed ratio within the photosynthetic intracytoplasmic membrane. Two proximal genes ( pufBA) specify subunits of a long wavelength absorbing (i.e., 875 nm) light harvesting complex which are present in the photosynthetic membrane in ≃15 fold excess relative to the reaction center subunits which are encoded by the pufLM genes. This review summarizes recent studies aimed at determining how expression of the R. sphaeroides puf operon region relates to the ratio of individual bacteriochlorophyll-protein complexes found within the photosynthetic membrane. These experiments indicate that puf operon expression may be regulated at the transcriptional, post-transcriptional, translation and post-translational levels. In addition, this review discusses the possible role(s) of newly identified loci upstream of pufB which may be involved in regulating either synthesis or assembly of individual bacteriochrlorophyll-protein complexes as well as the pufX gene, the most distal genetic element within the puf operon whose function is still unknown. [ABSTRACT FROM AUTHOR]

The roles of oxygen and light on the regulation of photosynthesis gene expression in Rhodobacter sphaeroides 2.4.1 have been well studied over the past 50 years. More recently, the effects of oxygen and light on gene regulation have been shown to involve the interacting redox chains present in R. sphaeroides under diverse growth conditions, and many of the redox carriers comprising these chains have been well studied. However, the expression patterns of those genes encoding these redox carriers, under aerobic and anaerobic photosynthetic growth, have been less well studied. Here, we provide a transcriptional analysis of many of the genes comprising the photosynthesis lifestyle, including genes corresponding to many of the known regulatory elements controlling the response of this organism to oxygen and light. The observed patterns of gene expression are evaluated and discussed in light of our knowledge of the physiology of R. sphaeroides under aerobic and photosynthetic growth conditions. Finally, this analysis has enabled to us go beyond the traditional patterns of gene expression associated with the photosynthesis lifestyle and to consider, for the first time, the full complement of genes responding to oxygen, and variations in light intensity when growing photosynthetically. The data provided here should be considered as a first step in enabling one to model electron flow in P. sphaeroides 2.4.1. [ABSTRACT FROM AUTHOR]

Studies the default state of the membrane-localized PrrB histidine kinase of prokaryote Rhodobacter sphaeroides. Genes involved in the positive regulation of photosynthesis; Proposed mechanism of the signal transduction pathway; Formation of spectral complex in PrrB mutants; Effect of negative gene autoregulation on gene expression.

The complex genome of Rhodobacter sphaeroides 2.4.1, composed of chromosomes I (CI) and II (CII), has been sequenced and assembled. We present data demonstrating that the R. sphaeroides genome possesses an extensive amount of exact DNA sequence duplication, 111 kb or ∼2.7% of the total chromosomal DNA. The chromosomal DNA sequence duplications were aligned to each other by using MUMmer. Frequency and size distribution analyses of the exact DNA duplications revealed that the interchromosomal duplications occurred prior to the intrachromosomal duplications. Most of the DNA sequence duplications in the R. sphaeroides genome occurred early in species history, whereas more recent sequence duplications are rarely found. To uncover the history of gene duplications in the R. sphaeroides genome, 44 gene duplications were sampled and then analyzed for DNA sequence similarity against orthologous DNA sequences. Phylogenetic analysis revealed that ∼80& of the total gene duplications examined displayed type A phylogenetic relationships; i.e., one copy of each member of a duplicate pair was more similar to its orthologue, found in a species closely related to R. sphaeroides, than to its duplicate, counterpart allele. The data reported here demonstrate that a massive level of gene duplications occurred prior to the origin of the R. sphaeroides 2.4.1 lineage. These findings lead to the conclusion that there is an ancient partnership between CI and CII of R. sphaeroides 2.4.1. [ABSTRACT FROM AUTHOR]