Complete Genome Sequence of the Photosynthetic Purple Nonsulfur Bacterium
            <i>Rhodobacter capsulatus</i>
            SB 1003

Strnad, Hynek; Lapidus, Alla; Pačes, Jan; Ulbrich, Pavel; Vlček, Čestmı́r; Pačes, Václav; Haselkorn, Robert

doi:10.1128/jb.00366-10

Cited by 92 publications

(62 citation statements)

References 15 publications

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“…This raises the question of how Mo is stored in the cells. A specific Mo storage protein similar to A. vinelandii MoSto (11, 44) does not exist in R. capsulatus (52). An R. capsulatus mutant defective for the Mop protein, which has been discussed as acting in Mo storage (37,57,58), accumulated Mo as efficiently as the wild type (data not shown).…”

Section: Discussionmentioning

confidence: 96%

“…Replacement of sulfate by the alternative sulfur sources taurine and cysteine, however, did not cure Mo inhibition in R. capsulatus. Since taurine and cysteine are taken up by independent transporters (28,52), we conclude that the sulfate transporter is not the main target for Mo inhibition in R. capsulatus. On the other hand, mutants defective for ATP sulfurylase were Mo tolerant like perO mutants, implying that the ATP sulfurylase reaction is unfavorable in the presence of high Mo concentrations.…”

Section: Discussionmentioning

confidence: 99%

“…R. capsulatus efficiently grows with these alternative sulfur sources, which are taken up by independent transporters (Fig. 6A) (28,52). Neither taurine nor cysteine cured Mo sensitivity (Fig.…”

Section: Identification Of Mo-tolerant R Capsulatus Mutants Growth mentioning

confidence: 99%

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A Rhodobacter capsulatus Member of a Universal Permease Family Imports Molybdate and Other Oxyanions

et al. 2010

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Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity, Rhodobacter capsulatus mutants tolerant to high Mo concentrations were isolated by random transposon Tn5 mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters, in vivo Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in R. capsulatus. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family.Molybdenum (Mo) is utilized by many bacteria, archaea, and eukaryotes as a cofactor of redox enzymes catalyzing key reactions in the nitrogen, sulfur, and carbon cycles (62). Nitrogenase, which catalyzes the reduction of dinitrogen to ammonia, carries the unique iron-molybdenum cofactor FeMoco. In contrast to nitrogenase, all other molybdoenzymes harbor the molybdenum cofactor Moco, which transfers either an oxo group or two electrons to or from the substrate in a wide variety of transformations at nitrogen, sulfur, and carbon atoms (47).The phototrophic alphaproteobacterium Rhodobacter capsulatus serves as a model organism to study Mo metabolism because it synthesizes several molybdoenzymes, including dimethyl sulfoxide reductase, xanthine dehydrogenase, and nitrogenase (29,30,46). In addition to Mo-dependent nitrogenase (Mo-nitrogenase), R. capsulatus uses an alternative, Mofree nitrogenase when Mo is limiting (55, 57). Two related Mo-responsive regulators, MopA and MopB, control expression of the alternative nitrogenase and molybdate uptake genes (22,57,58).Mo is available for living cells in its oxyanion form, molybdate. The vast majority of Mo-utilizing bacteria is known or predicted to possess ModABC-type high-affinity molybdate uptake systems (62, 63). These importers belong to the family of ATP-binding cassette (ABC) transporters, which couple ATP hydrolysis to substrate translocation across biological membranes (13, 15). ModABC transpor...

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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A Rhodobacter capsulatus Member of a Universal Permease Family Imports Molybdate and Other Oxyanions

et al. 2010

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“…Construction of expression vectors. The 1.97-kb Suden_619, 1.69-kb Suden_1879, 1.98-kb Suden_2082 (encoding type IV, III, and II SQRs from S. denitrificans, respectively, and including corresponding promoter regions [20,22]), and the 1.68-kb sqrRC (RCAP_rcc00785, encoding SQR from R. capsulatus SB1003, including its promoter region [35]) were amplified from the corresponding genomic DNA by using the primers listed in Table 2. The fragments were ligated with pGEM-T (Promega, Mannheim, Germany), restricted with the corresponding restriction enzymes (Table 2), and religated to restricted pRK415 (36).…”

Section: Methodsmentioning

confidence: 99%

Sulfide Consumption in Sulfurimonas denitrificans and Heterologous Expression of Its Three Sulfide-Quinone Reductase Homologs

Han

Perner

2016

J Bacteriol

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Sulfurimonas denitrificans is a sulfur-oxidizing epsilonproteobacterium. It has been reported to grow with sulfide and to harbor genes that encode sulfide-quinone reductases (SQRs) (catalyze sulfide oxidation). However, the actual sulfide concentrations at which S. denitrificans grows and whether its SQRs are functional remain enigmatic. Here, we illustrate the sulfide concentrations at which S. denitrificans exhibits good growth, namely, 0.18 mM to roughly 1.7 mM. Around 2.23 mM, sulfide appears to inhibit growth. S. denitrificans harbors three SQR homolog genes on its genome (Suden_2082 for type II SQR, Suden_1879 for type III SQR, and Suden_619 for type IV SQR). They are all transcribed in S. denitrificans. According to our experiments, they appear to be loosely bound to the membrane. Each individual S. denitrificans SQR was heterologously expressed in the Rhodobacter capsulatus SB1003 sqr deletion mutant, and all exhibited SQR activities individually. This suggests that all of these three genes encode functional SQRs. This study also provides the first experimental evidence of a functional bacterial type III SQR. IMPORTANCEAlthough the epsilonproteobacterium Sulfurimonas denitrificans has been described as using many reduced sulfur compounds as electron donors, there is little knowledge about its growth with sulfide. In many bacteria, the sulfide-quinone reductase (SQR) is responsible for catalyzing sulfide oxidation. S. denitrificans has an array of different types of sqr genes on its genome and so do several other sulfur-oxidizing Epsilonproteobacteria. However, whether these SQRs are functional has remained unknown. Here, we shed light on sulfide metabolism in S. denitrificans. Our study provides the first experimental evidence of active epsilonproteobacterial SQRs and also gives the first report of a functional bacterial type III SQR. Sulfide is a reduced sulfur compound present in nature (e.g., marine sediments and hydrothermal deep-sea vents [1-4]), and it can serve as an electron donor for many bacteria in their phototrophic and chemolithotrophic growth. Two enzymes have been reported for the oxidation of sulfide, sulfide-quinone reductase (SQR; EC 1.8.5.4) and flavocytochrome c (FCC; also known as sulfide-cytochrome c oxidoreductase). The electrons released from the oxidation of sulfide enter the photo-and chemolithotrophic electron transport chain either at the level of the quinone pool via SQR or at the level of cytochrome c via FCC (5). The two enzymes are sulfide-oxidizing flavoproteins, but metabolic energy generation with SQR is more efficient than that with FCC (5).SQRs are globally distributed and present in all three kingdoms (6-16). According to their structure-based sequence fingerprints, SQR enzymes have been classified into six types (i.e., SQR types I to VI) (16). In the last two decades, many of these SQR types have been studied in detail, e.g., type I SQRs from the alphaproteobacteria Rhodobacter capsulatus (6) and Paracoccus denitrificans (15), type II SQR from the nonpathoge...

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“…In particular, it is capable of using light energy to generate the ATP required for the energetically demanding nitrogen fixation process. R. capsulatus synthesizes two nitrogenases, namely, a Mo-nitrogenase and a Fenitrogenase but no V-nitrogenase (10,11). The synthesis and activity of the two nitrogenases are controlled at the transcriptional, translational, and posttranslational levels by a regulatory cascade responding to ammonium and Mo availability (8,9).…”

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confidence: 99%

Proteome Profiling of the Rhodobacter capsulatus Molybdenum Response Reveals a Role of IscN in Nitrogen Fixation by Fe-Nitrogenase

et al. 2016

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Rhodobacter capsulatus is capable of synthesizing two nitrogenases, a molybdenum-dependent nitrogenase and an alternative Mo-free iron-only nitrogenase, enabling this diazotroph to grow with molecular dinitrogen (N 2 ) as the sole nitrogen source. Here, the Mo responses of the wild type and of a mutant lacking ModABC, the high-affinity molybdate transporter, were examined by proteome profiling, Western analysis, epitope tagging, and lacZ reporter fusions. Biological nitrogen fixation (BNF) is a central process in the global nitrogen cycle, which converts chemically inert atmospheric dinitrogen to ammonia, a bioavailable form of nitrogen. BNF is catalyzed by complex metalloenzymes called nitrogenases, which are exclusively found in diazotrophic bacteria and archaea but not in eukaryotes (1). All diazotrophs synthesize a molybdenum-dependent nitrogenase containing an iron-molybdenum cofactor, FeMoco. In addition to Mo-nitrogenases, some bacteria synthesize alternative Mo-free nitrogenases, which contain either an iron-vanadium cofactor, FeVco, or an iron-only cofactor, FeFeco (2). Alternative nitrogenases are less efficient than Monitrogenases in terms of consumption of reducing power and ATP per molecule of N 2 fixed (3, 4). Consequently, diazotrophs preferentially utilize Mo-nitrogenase as long as sufficient molybdate, the only bioavailable form of molybdenum, is available. To support Mo-nitrogenase activity under Mo-limiting conditions, most diazotrophs synthesize a high-affinity molybdate transporter, ModABC (1).The purple nonsulfur alphaproteobacterium Rhodobacter capsulatus is known for its metabolic versatility, and it has been used for decades as a model organism to study photosynthesis, hydrogen production, and nitrogen fixation (5-9). In particular, it is capable of using light energy to generate the ATP required for the energetically demanding nitrogen fixation process. R. capsulatus synthesizes two nitrogenases, namely, a Mo-nitrogenase and a Fenitrogenase but no V-nitrogenase (10, 11). The synthesis and activity of the two nitrogenases are controlled at the transcriptional, translational, and posttranslational levels by a regulatory cascade responding to ammonium and Mo availability (8, 9). Upon ammonium limitation, the nitrogen regulatory protein NtrC becomes activated by phosphorylation. In turn, NtrC-P activates transcription of nifA and anfA, which encode the transcription activators of Mo-nitrogenase and Fe-nitrogenase genes, respectively. At high Mo concentrations, anfA transcription is repressed by two structurally and functionally related Mo-responsive regu-

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Complete Genome Sequence of the Photosynthetic Purple Nonsulfur Bacterium Rhodobacter capsulatus SB 1003

Cited by 92 publications

References 15 publications

A Rhodobacter capsulatus Member of a Universal Permease Family Imports Molybdate and Other Oxyanions

A Rhodobacter capsulatus Member of a Universal Permease Family Imports Molybdate and Other Oxyanions

Sulfide Consumption in Sulfurimonas denitrificans and Heterologous Expression of Its Three Sulfide-Quinone Reductase Homologs

Proteome Profiling of the Rhodobacter capsulatus Molybdenum Response Reveals a Role of IscN in Nitrogen Fixation by Fe-Nitrogenase

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