scholarly journals Adaptation to Photooxidative Stress: Common and Special Strategies of the Alphaproteobacteria Rhodobacter sphaeroides and Rhodobacter capsulatus

2020 ◽  
Vol 8 (2) ◽  
pp. 283 ◽  
Author(s):  
Mathieu K. Licht ◽  
Aaron M. Nuss ◽  
Marcel Volk ◽  
Anne Konzer ◽  
Michael Beckstette ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Specific Response ◽  
Light Conditions ◽  
Photooxidative Stress ◽  
Alternative Sigma Factors ◽  
Oxidation Reduction ◽  
Damage Repair ◽  
Photosynthetic Complexes ◽  
Individual Strategies ◽  
Phototrophic Growth

Photosynthetic bacteria have to deal with the risk of photooxidative stress that occurs in presence of light and oxygen due to the photosensitizing activity of (bacterio-) chlorophylls. Facultative phototrophs of the genus Rhodobacter adapt the formation of photosynthetic complexes to oxygen and light conditions, but cannot completely avoid this stress if environmental conditions suddenly change. R. capsulatus has a stronger pigmentation and faster switches to phototrophic growth than R. sphaeroides. However, its photooxidative stress response has not been investigated. Here, we compare both species by transcriptomics and proteomics, revealing that proteins involved in oxidation–reduction processes, DNA, and protein damage repair play pivotal roles. These functions are likely universal to many phototrophs. Furthermore, the alternative sigma factors RpoE and RpoHII are induced in both species, even though the genetic localization of the rpoE gene, the RpoE protein itself, and probably its regulon, are different. Despite sharing the same habitats, our findings also suggest individual strategies. The crtIB-tspO operon, encoding proteins for biosynthesis of carotenoid precursors and a regulator of photosynthesis, and cbiX, encoding a putative ferrochelatase, are induced in R. capsulatus. This specific response might support adaptation by maintaining high carotenoid-to-bacteriochlorophyll ratios and preventing the accumulation of porphyrin-derived photosensitizers.

scholarly journals Spectroscopic and oxidation–reduction properties of Rhodobacter capsulatus cytochrome c1 and its M183K and M183H variants

2002 ◽  
Vol 1556 (2-3) ◽  
pp. 175-186 ◽  
Author(s):  
Jun Li ◽  
Elisabeth Darrouzet ◽  
Ish K Dhawan ◽  
Michael K Johnson ◽  
Artur Osyczka ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Oxidation Reduction ◽  
Cytochrome C1

scholarly journals The Glutathione-Glutaredoxin System in Rhodobacter capsulatus: Part of a Complex Regulatory Network Controlling Defense against Oxidative Stress

2004 ◽  
Vol 186 (20) ◽  
pp. 6800-6808 ◽  
Author(s):  
Kuanyu Li ◽  
Silke Hein ◽  
Wenxin Zou ◽  
Gabriele Klug
Keyword(s):  
Oxidative Stress ◽  
Rhodobacter Capsulatus ◽  
Glutathione Synthetase ◽  
Lower Growth ◽  
E Coli ◽  
Oxidative Stress Defense ◽  
Highly Sensitive ◽  
Thioredoxin System ◽  
Photosynthetic Complexes ◽  
Stress Defense

ABSTRACT Mutants with defects in components of the glutathione-glutaredoxin (GSH/Grx) system of Rhodobacter capsulatus were constructed to study its role in defense against oxidative stress and the redox-dependent formation of photosynthetic complexes. The lack of the glutaredoxin 3 gene (grxC) or the glutathione synthetase B gene (gshB) resulted in lower growth rates under aerobic conditions and higher sensitivity to oxidative stress, confirming the role of the GSH/Grx system in oxidative stress defense. Both mutants are highly sensitive to disulfide stress, indicating a major contribution of the GSH/Grx system to the thiol-disulfide redox buffer in the cytoplasm. Like mutations in the thioredoxin system, mutations in the GSH/Grx system affected the formation of photosynthetic complexes, which is redox dependent in R. capsulatus. Expression of the genes grxC, gshB, grxA for glutaredoxin 1, and gorA for glutathione reductase, all encoding components of the GSH/Grx system, was not induced by oxidative stress. Other genes, for which a role in oxidative stress was established in Escherichia coli, acnA, fpr, fur, and katG, were strongly induced by oxidative stress in R. capsulatus. Mutations in the grxC, and/or gshB, and/or trxC (thioredoxin 2) genes affected expression of these genes, indicating an interplay of the different defense systems against oxidative stress. The OxyR and the SoxRS regulons control the expression of many genes involved in oxidative stress defense in E. coli in response to H2O2 and superoxide, respectively. Our data and the available genome sequence of R. capsulatus suggest that a SoxRS system is lacking but an alternative superoxide specific regulator exists in R. capsulatus. While the expression of gorA and grxA is regulated by H2O2 in E. coli this is not the case in R. capsulatus, indicating that the OxyR regulons of these two species are significantly different.

scholarly journals Carotenoid Biosynthetic Pathways Are Regulated by a Network of Multiple Cascades of Alternative Sigma Factors in Azospirillum brasilense Sp7

2016 ◽  
Vol 198 (21) ◽  
pp. 2955-2964 ◽  
Author(s):  
Ashutosh Kumar Rai ◽  
Ashutosh Prakash Dubey ◽  
Santosh Kumar ◽  
Debashis Dutta ◽  
Mukti Nath Mishra ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Biosynthetic Pathway ◽  
Sigma Factors ◽  
Photooxidative Stress ◽  
Gene Encoding ◽  
Content Type ◽  
Geranylgeranyl Pyrophosphate Synthase ◽  
Alternative Sigma Factors ◽  
Carotenoid Synthesis ◽  
Carotenoid Biosynthetic Pathway

ABSTRACTCarotenoids constitute an important component of the defense system against photooxidative stress in bacteria. InAzospirillum brasilenseSp7, a nonphotosynthetic rhizobacterium, carotenoid synthesis is controlled by a pair of extracytoplasmic function sigma factors (RpoEs) and their cognate zinc-binding anti-sigma factors (ChrRs). Its genome harbors two copies of the gene encoding geranylgeranyl pyrophosphate synthase (CrtE), the first critical step in the carotenoid biosynthetic pathway in bacteria. Inactivation of each of twocrtEparalogs found inA. brasilensecaused reduction in carotenoid content, suggesting their involvement in carotenoid synthesis. However, the effect ofcrtE1deletion was more pronounced than that ofcrtE2deletion. Out of the five paralogs ofrpoHinA. brasilense, overexpression ofrpoH1andrpoH2enhanced carotenoid synthesis. Promoters ofcrtE2andrpoH2were found to be dependent on RpoH2 and RpoE1, respectively. Using a two-plasmid system inEscherichia coli, we have shown that thecrtE2gene ofA. brasilenseSp7 is regulated by two cascades of sigma factors: one consisting of RpoE1and RpoH2 and the other consisting of RpoE2 and RpoH1. In addition, expression ofcrtE1was upregulated indirectly by RpoE1 and RpoE2. This study shows, for the first time in any carotenoid-producing bacterium, that the regulation of carotenoid biosynthetic pathway involves a network of multiple cascades of alternative sigma factors.IMPORTANCECarotenoids play a very important role in coping with photooxidative stress in prokaryotes and eukaryotes. Although extracytoplasmic function (ECF) sigma factors are known to directly regulate the expression of carotenoid biosynthetic genes in bacteria, regulation of carotenoid biosynthesis by one or multiple cascades of sigma factors had not been reported. This study provides the first evidence of the involvement of multiple cascades of sigma factors in the regulation of carotenoid synthesis in any bacterium by showing the regulation of a gene encoding geranylgeranyl pyrophosphate synthase (crtE2) by RpoE1→RpoH2→CrtE2 and RpoE2→RpoH1→CrtE2 cascades inA. brasilense. It also provides an insight into existence of an additional cascade or cascades regulating expression of another paralog ofcrtE.

The role of auxiliary oxidants in maintaining redox balance during phototrophic growth of Rhodobacter capsulatus on propionate or butyrate

1988 ◽  
Vol 150 (2) ◽  
pp. 131-137 ◽  
Author(s):  
David J. Richardson ◽  
Glenn F. King ◽  
David J. Kelly ◽  
Alastair G. McEwan ◽  
Stuart J. Ferguson ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Redox Balance ◽  
Phototrophic Growth

scholarly journals A Complex Network of Sigma Factors and sRNA StsR Regulates Stress Responses in R. sphaeroides

2021 ◽  
Vol 22 (14) ◽  
pp. 7557
Author(s):  
Katrin M. H. Eisenhardt ◽  
Bernhardt Remes ◽  
Julian Grützner ◽  
Daniel-Timon Spanka ◽  
Andreas Jäger ◽  
...  
Keyword(s):  
Stress Responses ◽  
Sigma Factors ◽  
Photooxidative Stress ◽  
Alternative Sigma Factors ◽  
Special Challenge ◽  
Photosynthesis Genes ◽  
In Vitro Interaction ◽  
Complex Regulatory Network

Adaptation of bacteria to a changing environment is often accompanied by remodeling of the transcriptome. In the facultative phototroph Rhodobacter sphaeroides the alternative sigma factors RpoE, RpoHI and RpoHII play an important role in a variety of stress responses, including heat, oxidative stress and nutrient limitation. Photooxidative stress caused by the simultaneous presence of chlorophylls, light and oxygen is a special challenge for phototrophic organisms. Like alternative sigma factors, several non-coding sRNAs have important roles in the defense against photooxidative stress. RNAseq-based transcriptome data pointed to an influence of the stationary phase-induced StsR sRNA on levels of mRNAs and sRNAs with a role in the photooxidative stress response. Furthermore, StsR also affects expression of photosynthesis genes and of genes for regulators of photosynthesis genes. In vivo and in vitro interaction studies revealed that StsR, that is under control of the RpoHI and RpoHII sigma factors, targets rpoE mRNA and affects its abundance by altering its stability. RpoE regulates expression of the rpoHII gene and, consequently, expression of stsR. These data provide new insights into a complex regulatory network of protein regulators and sRNAs involved in defense against photooxidative stress and the regulation of photosynthesis genes.

scholarly journals Gene transfer agents: Another step towards a mechanistic understanding of expression

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
David Sherlock ◽  
Millie Benn ◽  
Paul Fogg
Keyword(s):  
Gene Transfer ◽  
Sigma Factor ◽  
Rhodobacter Capsulatus ◽  
Site Directed Mutagenesis ◽  
Regulatory Pathways ◽  
Protein Protein Interaction ◽  
Alternative Sigma Factors ◽  
Potential Impact ◽  
Two Hybrid ◽  
Transfer Agents

Gene transfer agents (GTAs) are small viruses that package and transfer random pieces of the producing cell’s genome but are unable to transfer all the genes required for their own production. GTAs are able to spread any DNA in the host cell and so their potential impact upon bacterial evolution and antimicrobial resistance is immense. Our discovery that the product of gene rcc01865 is a specific GTA activation factor (GafA) for the model Rhodobacter capsulatus GTA (RcGTA) and that GafA is essential for RcGTA production, has provided the link between GTA production and host regulatory pathways. However, while GafA has significantly improved our understanding of GTA regulation the complete mechanism is unclear. Our goal was to investigate the GafA mechanism of action in more detail. We demonstrate direct protein-protein interaction between GafA and the RNA polymerase omega subunit (RNAP Ω) using bacterial-two-hybrid and pull down assays. Further evidence for the interaction has come from random and site directed mutagenesis of gafA and targeted truncations. GafA mutants were also tested to assess their impact on RcGTA production. RNAP Ω is thought to recruit alternative sigma factors to the RNAP holoenzyme. Regions of GafA also share sequence homology with known sigma factor proteins, and we propose that GafA acts as an alternative sigma factor to co-ordinate expression of disparate RcGTA genes. Our results advance our understanding of this fascinating mode of horizontal gene transfer, not only in the model species but also in other potential GTA producing species that contain gafA homologues.

scholarly journals RNase E cleavage shapes the transcriptome ofRhodobacter sphaeroidesand strongly impacts phototrophic growth

2018 ◽  
Vol 1 (4) ◽  
pp. e201800080 ◽  
Author(s):  
Konrad U Förstner ◽  
Carina M Reuscher ◽  
Kerstin Haberzettl ◽  
Lennart Weber ◽  
Gabriele Klug
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Oxidative Stress Response ◽  
Cleavage Sites ◽  
Rnase E ◽  
Rna Seq ◽  
Rapid Changes ◽  
Photosynthetic Complexes ◽  
Phototrophic Growth

Bacteria adapt to changing environmental conditions by rapid changes in their transcriptome. This is achieved not only by adjusting rates of transcription but also by processing and degradation of RNAs. We applied TIER-Seq (transiently inactivating an endoribonuclease followed by RNA-Seq) for the transcriptome-wide identification of RNase E cleavage sites and of 5′ RNA ends, which are enriched when RNase E activity is reduced inRhodobacter sphaeroides. These results reveal the importance of RNase E for the maturation and turnover of mRNAs, rRNAs, and sRNAs in this guanine-cytosine-rich α-proteobacterium, some of the latter have well-described functions in the oxidative stress response. In agreement with this, a role of RNase E in the oxidative stress response is demonstrated. A remarkably strong phenotype of a mutant with reduced RNase E activity was observed regarding the formation of photosynthetic complexes and phototrophic growth, whereas there was no effect on chemotrophic growth.

The assimilatory nitrate reduction system of the phototrophic bacterium Rhodobacter capsulatus E1F1

2006 ◽  
Vol 34 (1) ◽  
pp. 127-129 ◽  
Author(s):  
C. Pino ◽  
F. Olmo-Mira ◽  
P. Cabello ◽  
M. Martínez-Luque ◽  
F. Castillo ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Nitrate Assimilation ◽  
Growth Conditions ◽  
Biochemical Properties ◽  
Regulatory Proteins ◽  
Structural Genes ◽  
Phototrophic Bacterium ◽  
Nitrate Sensor ◽  
Assimilatory Nitrate Reduction ◽  
Phototrophic Growth

The phototrophic bacterium Rhodobacter capsulatus E1F1 assimilates nitrate under anaerobic phototrophic growth conditions. A 17 kb DNA region encoding the nitrate assimilation (nas) system of this bacterium has been cloned and sequenced. This region includes the genes coding for a putative ABC (ATP-binding cassette)-type nitrate transporter (nasFED) and the structural genes for the enzymes nitrate reductase (nasA), nitrite reductase (nasB) and hydroxylamine reductase (hcp). Three genes code for putative regulatory proteins: a nitrite-sensitive repressor (nsrR), a transcription antiterminator (nasT) and a nitrate sensor (nasS). Other genes probably involved in nitrate assimilation are also present in this region. The sequence analysis of these genes and the biochemical properties of the purified nitrate, nitrite and hydroxylamine reductases are reviewed.

scholarly journals Distribution of the Water-Soluble Astaxanthin Binding Carotenoprotein (AstaP) in Scenedesmaceae

Marine Drugs ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. 349
Author(s):  
Hiroki Toyoshima ◽  
Ami Miyata ◽  
Risako Yoshida ◽  
Taichiro Ishige ◽  
Shinichi Takaichi ◽  
...  
Keyword(s):  
Water Soluble ◽  
Stress Conditions ◽  
Soluble Form ◽  
Light Conditions ◽  
Photooxidative Stress ◽  
Gene Encoding ◽  
Chlorella Variabilis ◽  
Cell Extracts ◽  
The Family ◽  
Genes Encoding

Photooxidative stress-inducible water-soluble astaxanthin-binding proteins, designated as AstaP, were identified in two Scenedesmaceae strains, Coelastrella astaxanthina Ki-4 and Scenedesmus obtusus Oki-4N; both strains were isolated under high light conditions. These AstaPs are classified as a novel family of carotenoprotein and are useful for providing valuable astaxanthin in water-soluble form; however, the distribution of AstaP orthologs in other microalgae remains unknown. Here, we examined the distribution of AstaP orthologs in the family Scenedesmaceae with two model microalgae, Chlamydomonas reinhardtii and Chlorella variabilis. The expression of AstaP orthologs under photooxidative stress conditions was detected in cell extracts of Scenedesmaceae strains, but not in model algal strains. Aqueous orange proteins produced by Scenedesmaceae strains were shown to bind astaxanthin. The protein from Scenedesmus costatus SAG 46.88 was purified. It was named ScosAstaP and found to bind astaxanthin. The deduced amino acid sequence from a gene encoding ScosAstaP showed 62% identity to Ki-4 AstaP. The expression of the genes encoding AstaP orthologs was shown to be inducible under photooxidative stress conditions; however, the production amounts of AstaP orthologs were estimated to be approximately 5 to 10 times lower than that of Ki-4 and Oki-4N.

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