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Two arsenic-resistant purple non-sulphur bacteria (PNSB), Q3B and Q3C, were isolated (from industrial contaminated site and paddy fields) and identified by SSU rRNA gene sequencing as Rhodospirillum and Rhodospirillaceae species, respectively. Maximum arsenic reduction by these PNSB was observed in anaerobic conditions. Rhodospirillum sp. Q3B showed 74.92% (v/v) arsenic reduction while Rhodospirillaceae sp. Q3C reduced arsenic up to 76.67% (v/v) in anaerobic conditions. Rhodospirillaceae sp. Q3C was found to contain highest carotenoid content up to 5.6 mg·g−1. Under anaerobic conditions, the isolates were able to respire arsenic in the presence of lactate, citrate, and oxalate. Rhodospirillum sp. Q3B and Rhodospirillaceae sp. Q3C were also found to produce hydrogen gas. Such diverse bacteria can be useful tools for bioremediation purposes. These bacteria can be further exploited and optimized to treat wastewater containing arsenic along with bio-hydrogen production. [ABSTRACT FROM AUTHOR]

Rhodospirillum rubrum l -asparaginase mutant RrA E149R, V150P, F151T (RrA) was previously identified to down-regulate telomerase activity along with catalyzing the hydrolysis of l -asparagine. The aim of this study was to define the effect of prolonged RrA exposure on telomerase activity, maintenance of telomeres and proliferation of cancer cells in vitro and in vivo . RrA could inhibit telomerase activity in SCOV-3, SkBr-3 and A549 human cancer cell lines due to its ability to down-regulate the expression of telomerase catalytic subunit hTERT. Telomerase activity in treated cells did not exceeded 29.63 ± 12.3% of control cells. Continuous RrA exposure of these cells resulted in shortening of telomeres followed by cell death in vitro . Using real time PCR we showed that length of telomeres in SCOV-3 cells has been gradually decreasing from 10105 ± 2530 b.p. to 1233 ± 636 b.p. after 35 days of cultivation. RrA treatment of xenograft models in vivo showed slight inhibition of tumor growth accompanied with 49.5–53.3% of decrease in hTERT expression in the all tumors. However down-regulation of hTERT expression, inhibition of telomerase activity and the loss of telomeres was significant in response to RrA administration in xenograft models. These results should facilitate further investigations of RrA as a potent therapeutic protein. [ABSTRACT FROM AUTHOR]

Wild strains of purple non-sulphur bacteria: Rhodospirillum rubrum B-6505, Rhodopseudomonas palustris B-6506, Rhodobacter capsulatus B-6508 and Rhodobacter spheroides B-6509 were studied as 5-ALA (5 aminolevulinic acid) producers. Selected strains were subjected to mutagenesis with N-methyl-N-nitro-N-nitrosoguanidine to obtain a strain with high 5-ALA producing capacity. After mutagenesis 19 stable mutant strains were selected from Rhodobacter capsulatus B-6508 and Rhodobacter sphaeroides B-6509. On the basis of obtained results, mutant strain of Rhodobacter capsulatus B-6508 has shown the highest potential for 5-ALA production. The most favorable conditions for growth and 5-ALA production by mutant strain R. capsulatus B-6508 were observed in media composed of glutamate and malate, light at 2000 Lux, microaerophilic conditions and temperature of 28 °C. In these conditions, the highest 5-ALA concentration (179 mg/L) was detected together with the highest bacterial physiological activity. The prolongation of mutant strain R. capsulatus B-6508 cultivation time after glycine, succinate and levulinic acid addition is related to the reduction of 5-ALA concentrations (e.g. 124.5 mg/L after 48 h and 89.5 mg/L after 72 hours). In the light/aerobic conditions R. capsulatus B-6508 produced only 58.1 mg/L of 5 ALA. Furthermore, in dark conditions even lower biomass and 5-ALA concentrations were observed during R. capsulatus B-6508 cultivation. [ABSTRACT FROM AUTHOR]

What follows are snapshots of my career in chicken eyes, yeast and Rhodospirillum rubrum, castor beans, Escherichia coli and finally yeast again. In contrast, only a few of the failures that realistically make up a career are included. It is a tale of the generosity and influences of those who shaped what I am and what I learned in a wonderful profession. The science described is only that which I was lucky enough to do or was performed in my laboratory by those who really deserve the credit for any success that I've enjoyed. Not mentioned for lack of space are the critical contributions of many impressive investigators in the field of nitrogen-responsive regulation for no scientific investigation occurs in isolation. [ABSTRACT FROM AUTHOR]

In this work, crude glycerol, a by-product from a biodiesel industry was characterized and converted to microbial lipid. The sample of crude glycerol was found to contain 44.56 wt.% glycerol, 13.86 wt.% methanol, 10.74 wt.% of ash and 32.97 wt.% of soap. Rhodosporidium toruloides ATCC 10788 was studied for the first time to determine its ability to grow on crude glycerol as a carbon source. Methanol concentration as low as 0.5% (w/v) in the medium containing pure glycerol inhibited biomass and lipid production by this strain. However, higher concentration of methanol (i.e. 1.5% w/v) in crude glycerol containing media did not have the same effect on the organism, with double the biomass (21.16 g/L), triple the lipid concentration (11.27 g/L) and high lipid content (53.28 wt.%) produced at the end of 168 h. Unlike many other oleaginous microorganisms, the ability of this yeast to consume other impurities present in crude glycerol enhanced the growth and lipid production in such a way that the effect of methanol was masked or became insignificant. The lipid obtained contained 47.16% of oleic acid (a monounsaturated fatty acid), making it a very good feedstock for some oleochemical industries and the production of biodiesel. This bioconversion process which involves the production of lipid from crude glycerol waste stream will be of great interest to the biodiesel industry as it can be easily integrated into the existing biodiesel production plant. The use of such robust strains to produce other value added products can also be explored. [ABSTRACT FROM AUTHOR]

Background: Several Gram-negative species undergo development leading to the formation of metabolically dormant desiccation resistant cysts. Recent analysis of cyst development has revealed that ~20 % of the Rhodospirillum centenum transcriptome undergo temporal changes in expression as cells transition from vegetative to cyst forms. It has also been established that one trigger for cyst formation is the synthesis of the signaling nucleotide 3', 5'- cyclic guanosine monophosphate (cGMP) that is sensed by a homolog of the catabolite repressor protein called CgrA. CgrA in the presence of cGMP initiate a cascade of gene expression leading to the development of cysts. Results: In this study, we have used RNA-seq and chromatin immunoprecipitation (ChIP-Seq) techniques to define the CgrA-cGMP regulon. Our results indicate that disruption of CgrA leads to altered expression of 258 genes, 131 of which have been previously reported to be involved in cyst development. ChIP-seq analysis combined with transcriptome data also demonstrates that CgrA directly regulates the expression of numerous sigma factors and transcription factors several of which are known to be involved in cyst cell development. Conclusions: This analysis reveals the presence of CgrA binding sites upstream of many developmentally regulated genes including many transcription factors and signal transduction components. CgrA thus functions as master controller of the cyst development by initiating a hierarchal cascade of downstream transcription factors that induces temporal expression of encystment genes. [ABSTRACT FROM AUTHOR]

Background: Rhodospirillum centenum is a photosynthetic member of the Gram-negative Azospirillum clade members of which exhibit a complex developmental life-cycle featuring morphologically distinct cell types. Under periods of nutrient deprivation, replicative vegetative cells differentiate into metabolically dormant cysts that survive harsh environmental stresses such as desiccation. Encystment involves a multi-stage developmental process that includes the rounding of cells, production of large intracellular storage granules of poly-hydroxybutyrate (PHB) and the excretion of a protective exopolysaccharide coating that envelops dormant cysts. Results: To study the process of cyst development, we performed RNA-seq studies on cells that were induced to undergo cyst development. To assay for temporal changes in gene expression, RNA was extracted at 4, 24, 48, 72, 96 hours during development and subjected to deep sequence analysis. These results show that 812 genes exhibit log2 ≥ 1.5-fold changes in expression over a 96 hour cyst induction period demonstrating large global changes in gene expression during cyst development. Conclusions: Notable changes in expression occurred in numerous genes involved in cell wall and lipid biosynthesis, metabolic enzymes, and numerous regulatory genes such as histidine kinases and transcription factors. Many genes involved in protein synthesis and DNA replication were also significantly reduced during late stages of cyst development. Genes previously identified by genetic screens as being critical for cyst development also exhibited changes of expression during cyst induction. This study provides the first transcriptome profile of global changes in gene expression that occur during development of cysts in a Gram-negative species. [ABSTRACT FROM AUTHOR]

The application of Rhodospirillum toruloides strain allowed resolving the chemically synthesized racemic mixtures of following chiral aminophosphonic acids: 1-aminoethylphosphonic acid (1), 1-amino-1- iso-propyl-1-phosphonic acid (2), 1-amino-1-phenylmethylphosphonic acid (4) and 1-amino-2-phenylethylphosphonic acid (3). The applied protocols resulted in obtaining pure ( R)-1-aminoethylphosphonic acid (100 % of e.e.) and enantiomerically enriched mixtures of other phosphonates (73 % e.e. of ( S)-1-amino-1-phenylmethylphosphonic acid, 51 % e.e. of ( R)-1-amino-2-phenylethylphosphonic acid and 40 % e.e. of ( S)-1-amino-2-methylpropylphosphonic acid). Products are valuable chiral building blocks and serve as aminophosphonic acids platform for further applications. Performed experiments allowed to define the path of xenobiotics bioconversion. [ABSTRACT FROM AUTHOR]

Genomic and genetic analyses have demonstrated that many species contain multiple chemotaxis-like signal transduction cascades that likely control processes other than chemotaxis. The Che3 signal transduction cascade from Rhodospirillum centenum is one such example that regulates development of dormant cysts. This Che-like cascade contains two hybrid response regulator-histidine kinases, CheA3 and CheS3, and a single-domain response regulator CheY3. We demonstrate that cheS3 is epistatic to cheA3 and that only CheS3∼P can phosphorylate CheY3. We further show that CheA3 derepresses cyst formation by phosphorylating a CheS3 receiver domain. These results demonstrate that the flow of phosphate as defined by the paradigm E. coli chemotaxis cascade does not necessarily hold true for non-chemotactic Che-like signal transduction cascades. [ABSTRACT FROM AUTHOR]

This study investigated the apparent genetic redundancy in the biosynthesis of polyhydroxyalkanoates (PHAs) in the Rhodospirillum rubrum genome revealed by the occurrence of three homologous PHA polymerase genes (phaC1, phaC2, and phaC3). In vitro biochemical assays established that each gene product encodes PHA polymerase. A series of single, double, and triple phaC deletion mutants were characterized with respect to PHA production and growth capabilities on acetate or hexanoate as the sole carbon source. These analyses establish that phaC2 contributes the major capacity to produce PHA, even though the PhaC2 protein is not the most efficient PHA polymerase biocatalyst. In contrast, phaC3 is an insignificant contributor to PHA productivity, and phaC1, the PHA polymerase situated in the PHA biosynthetic operon, plays a minor role in this capability, even though both of these genes encode PHA polymerases that are more efficient enzymes. These observations are consistent with the finding that PhaCl and PhaC3 occur at undetectable levels, at least 10-fold lower than that of PhaC2. The monomers in the PHA polymer produced by these strains establish that PhaC2 is responsible for the incorporation of the C5 and C6 monomers. The in vitro characterizations indicate that heteromeric PHA polymerases composed of mixtures of different PhaC paralogs are more efficient catalysts, suggesting that these proteins form complexes. Finally, the physiological role of PHA accumulation in enhancing the fitness of R. rubrum was indicated by the relationship between PHA content and growth capabilities of the genetically manipulated strains that express different levels of the PHA polymer. [ABSTRACT FROM AUTHOR]

Abstract: The model photosynthetic bacterium Rhodobacter sphaeroides uses a network of bacteriochlorophyll (BChl)–protein complexes embedded in spherical intracytoplasmic membranes (ICM) to collect and utilise solar energy. We studied the effects of high- and low-light growth conditions, where BChl levels increased approximately four-fold from 1.6×106 to 6.5×106 molecules per cell. Most of this extra pigment is accommodated in the proliferating ICM system, which increases from approximately 274 to 1468 vesicles per cell. Thus, 16×106 nm2 of specialised membrane surface area is made available for harvesting and utilising solar energy compared to 3×106 nm2 under high-light conditions. Membrane mapping using atomic force microscopy revealed closely packed dimeric and monomeric reaction centre-light harvesting 1-PufX (RC-LH1-PufX) complexes in high-light ICM with room only for small clusters of LH2, whereas extensive LH2-only domains form during adaptation to low light, with the LH2/RC ratio increasing three-fold. The number of upper pigmented band (UPB) sites where membrane invagination is initiated hardly varied; 704 (5.8×105 BChls/cell) and 829 (4.9×105 BChls/cell) UPB sites per cell were estimated under high- and low-light conditions, respectively. Thus, the lower ICM content in high-light cells is a consequence of fewer ICM invaginations reaching maturity. Taking into account the relatively poor LH2-to-LH1 energy transfer in UPB membranes it is likely that high-light cells are relatively inefficient at energy trapping, but can grow well enough without the need to fully develop their photosynthetic membranes from the relatively inefficient UPB to highly efficient mature ICM. [Copyright &y& Elsevier]

Abstract: Carotenoids play important roles in photosynthesis where they are involved in light-harvesting, in photo-protection and in the assembly and structural stability of light-harvesting and reaction centre complexes. In order to examine the effects of carotenoids on the oligomeric state of the reaction centre–light-harvesting 1 -PufX (RC–LH1–PufX) core complex of Rhodobacter sphaeroides two carotenoid-less mutants, TC70 and R-26, were studied. Detergent fractionation showed that in the absence of carotenoids LH2 complexes do not assemble, as expected, but also that core complexes are predominantly found as monomers, although levels of the PufX polypeptide appeared to be unaffected. Analysis of R-26 membranes by electron microscopy and atomic force microscopy reveals arrays of hexagonally packed monomeric RC–LH1–PufX complexes. Transfer of the crtB gene encoding phytoene synthase to TC70 and R-26 restores the normal synthesis of carotenoids demonstrating that the R-26 mutant of Rba. sphaeroides harbours a mutation in crtB, among its other defects. The transconjugant TC70 and R-26 strains containing crtB had regained their ability to assemble wild-type levels of dimeric RC–LH1–PufX core complexes and normal energy transfer pathways were restored, demonstrating that carotenoids are essential for the normal assembly and function of both the LH2 and RC–LH1–PufX complexes in this bacterial photosystem. [Copyright &y& Elsevier]

The α-proteobacterium, Rhodospirillum centenum, has a complex life cycle that allows adaptation to different environments. Transitions between vegetative swim cell and swarmer cell types depend on whether the organism is growing in liquid surroundings or on a solid substrate. Moreover, starvation can induce vegetative cells to differentiate into quiescent cysts. This paper describes the results of our investigation into the role of a putative DNA-binding response regulator that is homologous to CtrA, the cell cycle regulator from Caulobacter crescentus. Deletion of ctrA from the R. centenum genome resulted in a viable strain with impaired swarming motility coupled with an increased tendency to form cysts. Conversely, overexpression of wild type CtrA or a phosphomimetic allele, CtrAD51E, suppressed cyst cell formation, whereas overexpression of a CtrAD51A allele failed to suppress encystment but did prevent swarming motility. Thus, we propose that CtrA participates within a two-component signal transduction pathway that promotes swarming motility while contributing to the suppression of cyst cell formation. [ABSTRACT FROM AUTHOR]

We have studied the triplet energy transfer (TET) for photosynthetic light-harvesting complexes, the bacterial light-harvesting complex II (LH2) of Rhodospirillum molischianum and Rhodopseudomonas acidophila, and the peridinin -chlorophyll a protein (PCP) from Amphidinium carterae. The electronic coupling factor was calculated with the recently developed fragment spin difference scheme (You and Hsu, J. Chem, Phys. 2010, 133, 074105), which is a general computational scheme that yields the overall coupling under the Hamiltonian employed. The TET rates were estimated based on the couplings obtained. For all light-harvesting complexes studied, there exist nanosecond triplet energy transfer from the chlorophylls to the carotenoids. This result supports a direct triplet quenching mechanism for the photoprotection function of carotenoids. The TET rates are similar for a broad range of carotenoid triplet state energy, which implies a general and robust TET quenching role for carotenoids in photosynthesis. This result is also consistent with the weak dependence of TET kinetics on the type or the number of π conjugation lengths in the carotenoids and their analogues reported in the literature. We have also explored the possibility of forming triplet excitons in these complexes. In B850 of LH2 or the peridinin cluster in PCP, it is unlikely to have triplet exciton since the energy differences of any two neighboring molecules are likely to be much larger than their TET couplings. Our results provide theoretical limits to the possible photophysics in the light-harvesting complexes. [ABSTRACT FROM AUTHOR]

The author describes the role of Alphaproteobacterium Rhodospirillum centenum in the developmental process of synthesizing cyclic guanosine monophosphate (cGMP), based on a study by Carl Bauer from Indiana University and his colleagues, published in this issue of "Molecular Microbiology." The researchers identified two transposon insertions in a gene encoding a class III nucleotidyl cyclase. They used the encystment process to measure intracellular and extracellular levels of cGMP and cyclic adenosine monophosphate (cAMP).

Adenylyl cyclases are widely distributed across all kingdoms whereas guanylyl cyclases are generally thought to be restricted to eukaryotes. Here we report that the α-proteobacterium Rhodospirillum centenum secretes cGMP when developing cysts and that a guanylyl cyclase deletion strain fails to synthesize cGMP and is defective in cyst formation. The R. centenum cyclase was purified and shown to effectively synthesize cGMP from GTP in vitro, demonstrating that it is a functional guanylyl cyclase. A homologue of the Escherichia coli cAMP receptor protein (CRP) is linked to the guanylyl cyclase and when deleted is deficient in cyst development. Isothermal calorimetry (ITC) and differential scanning fluorimetry (DSF) analyses demonstrate that the recombinant CRP homologue preferentially binds to, and is stabilized by cGMP, but not cAMP. This study thus provides evidence that cGMP has a crucial role in regulating prokaryotic development. The involvement of cGMP in regulating bacterial development has broader implications as several plant-interacting bacteria contain a similar cyclase coupled by the observation that Azospirillum brasilense also synthesizes cGMP when inducing cysts. [ABSTRACT FROM AUTHOR]

Abstract: MCM41 nanoparticles with or without mercaptopropyl functional groups were added to a synthesis gas fermentation reactor to investigate their influence on syngas fermentation. Carbon monoxide was fermented using Rhodospirillum rubrum (R. rubrum), resulting in an enhanced H2 concentration in the product gas as a result of a biologically mediated water–gas shift (WGS) reaction. The results indicated that the H2 yield was enhanced by ∼200% when 0.6 wt% of the MCM41 nanoparticles functionalized with 5% molar ratio of mercaptopropyl group were added to the reactor. These results complement previous studies and suggest that the increased H2 yield is due to enhanced CO–water mass transfer through the addition of the functionalized MCM41 nanoparticles. [ABSTRACT FROM AUTHOR]