Rhodocyclus Gelatinosus Research Articles

Decolorization of Reactive Brilliant Blue KN-R by Immobilized Cells of <i>Rhodocyclus gelatinosus</i>

Reactive Brilliant Blue KN-R is a typical kind of anthraquinone dye and in common use in textile, dyeing, and printing industries in China, which is difficult to degrade because of its conjugated structure. The decolorization of KN-R was investigated using Ca-alginate immobilized cells of Rhodocyclus gelatinosus XL-1 under anaerobic conditions. For KN-R decolorization by immobilized cells, the suitable pH is 5-8 and the suitable temperature is 25-40 °C. Immobilized cells could decolorize KN-R by co-metabolism in the presence of peptone, and the enhancement of peptone concentration was beneficial for anaerobic decolorization. Metal ions affected the metabolic activity of immobilized cells of R. gelatinosus XL-1. The activity of KN-R decolorization was appreciably increased by Mg2+ and Cr3+, but severely inhibited by Cu2+ and Ag+. The maximum absorption peak in visible spectrum shifted from 595 to 453 nm during KN-R decolorization, indicating the formation of the intermediate product.

Ecological role of thiosulfate and sulfide utilizing purple nonsulfur bacteria of a riverine ecosystem

The screening of purple nonsulfur bacteria (PNSB) from the polluted and unpolluted zones of the river Ganga and from the discharged effluents (pollutants), revealed that the population densities of PNSB were highest in the discharged pollutants followed by polluted and unpolluted river waters in decreasing order. The allochthonous input of PNSB affected the ambient PNSB population. In all the monitored sites, the PNSB population utilizing malate as electron donor was higher than those utilizing thiosulfate or sulfide or both as electron donors. The physico-chemical parameters of the river water related to the distribution of PNSB were recorded. Twenty-four isolates of PNSB utilizing sulfide and thiosulfate, assigned to Rhodopseudomonas palustris including a morphophysiological variant of the species, Rhodobacter capsulatus and Rhodocyclus gelatinosus (=Rubrivivax gelatinosus), were screened from river Ganga. The surviving ability of PNSB population under simulated condition differed amongst the monitored sites. The isolated strains of PNSB were able to convert thiosulfate to sulfate or to elemental sulfur and also were able to oxidize sulfide. However, there was heterogeneity with respect to the rates at which they transformed these sulfur compounds. The overall thiosulfate transformation rate by the PNSB isolates in the river water was 117.3 μmol d−1 mg−1 and that of sulfide transformation was in the order of 0.15 μmol d−1 mg−1. The ecological significance of sulfide utilization in the aquatic bodies by the isolates of PNSB is discussed.

Performance and color of broilers fed diets containing Rhodocyclus gelatinosus biomass

The objective of this study was to evaluate the effect of different supplementation levels of Rhodocyclus gelatinosus biomass on the performance and pigmentation of broilers. Cobb broilers were raised in pens and were fed a sorghum-based diet until 35 days of age. At the 36th day of age, ninety-six birds were randomly distributed to four treatments consisting of experimental diets with different supplementation levels of Rhodocyclus gelatinosus biomass (0, 75, 150 and 300 ppm) added to the finisher basal diet, which were given for seven days. A completely randomized experimental design was used, with four treatments, four replicates and six broilers per parcel. Birds and diets were weighed at the 36th and at the 42nd day of age for performance analysis. There was no significant effect on broiler feed intake. Significant differences in weight gain and feed conversion were seen between the control group and the groups supplemented with 75 and 150 ppm. The treatment with the highest supplementation level and the control group had best weight gain and feed conversion. Color analysis showed that R. gelatinosus biomass supplementation resulted in more yellow breast skin and increased darkening and color purity in breast and thigh meat of broilers, but had no effect on lightness or color purity of breast and thigh skins.

Rhodocyclus gelatinosus Biomass for Egg Yolk Pigmentation

Biomass of the photosynthetic bacterium Rhodocyclus gelatinosus was used at different levels in laying hens’ rations as a xanthophyll source. Sixty-four hens were used in the experiment that investigated the effects of different biomass concentrations on weight gain, egg production, egg weight, and yolk color as compared with a control group that received no biomass supplementation in the ration. Yolk color was scored by means of a color fan. All concentrations tested were able to provide yolk color scores higher than those provided by the control group. The pigment deposition began after 24 h of administration and reached a plateau around the twentieth day. Each increase in the supplementation level led to an additional increase on yolk color scores. Yolk colors of all treatments that received R. gelatinosus biomass differed significantly from the control group and from each other, corroborating that the increase in the biomass supplementation had a positive effect on color increase. Body weight loss occurred in all treatments. Egg production did not increase with the biomass addition, while a significant increase in egg weight was observed in the treatments that received the product.

Peptone-induced biodecolorization of Reactive Brilliant Blue (KN-R) by Rhodocyclus gelatinosus XL-1

A strain of Rhodocyclus gelatinosus (XL-1) from textile wastewater could decolorized Reactive Brilliant Blue (KN-R) under anaerobic conditions. XL-1 could not decolorize KN-R when it was the sole carbon source. In the presence of peptone, it could decolorize KN-R over 93% by co-metabolism at pH 7.0 and temperature 30 °C. Decolorization efficiency rose greatly at a fixed concentration of KN-R (50 mg/l) along with an increase in peptone concentration. Dye concentration had an influence on the decolorization rate, with an increase in the KN-R concentration, the decolorization rate increased. After 24 h, the KN-R concentrations in wastewater, which started with different initial values, had a tendency to a uniform value. Metal compounds, especially, AgNO 3, HgCl 2, ZnSO 4, CuSO 4, had a severe inhibitory effect on decolorization of KN-R: 1 mmol/l led to about 98% drop in decolorization efficiency, but MgSO 4 and MnSO 4 could appreciably increase decolorization of KN-R. The ultraviolet–visible absorbance spectra of the products were determined and the maximum absorption peak in visible spectrum shifted from 595 to 453 nm.

Chemical composition of Rhodocyclus gelatinosus biomass produced in poultry slaughterhouse wastewater

Rhodocyclus gelatinosus R1 grew photoautotrophically in poultry slaughterhouse wastewater inside glass columns (90x670 mm) during 7 days at 31 ± 4ºC, under anaerobiosis and lightness supplied by daylight plus 3 (100W) incandescent and 4 (40W) fluorescent lamps. The culture was centrifuged (4,500xg/20 min) and lyophilized to originate a bacterial biomass with 7.1% moisture content. Chemical composition investigation showed 67.6% crude protein, 27.6% total carbohydrate, 0.6% lipids and 4.2% ash (dry weight). Amino acid composition of the biomass was similar to others described in the literature for Rhodocyclus gelatinosus and for other photosynthetic bacteria. Effluent COD removal after cultivation and elimination of the biomass was around 90%. The valuable chemical composition of Rhodocyclus gelatinosus R1 biomass and the high content in essential amino acids signs for the potential use of the product in poultry feed.

Isolation and Molecular Characterization of pMG160, a Mobilizable Cryptic Plasmid from Rhodobacter blasticus

A 3.4-kb cryptic plasmid was obtained from a new isolate of Rhodobacter blasticus. This plasmid, designated pMG160, was mobilizable by the conjugative strain Escherichia coli S17.1 into Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas palustris. It replicated in the latter strains but not in Rhodospirillum rubrum, Rhodocyclus gelatinosus, or Bradyrhizobium species. Plasmid pMG160 was stably maintained in R. sphaeroides for more than 100 generations in the absence of selection but showed segregational instability in R. palustris. Instability in R. palustris correlated with a decrease in plasmid copy number compared to the copy number in R. sphaeroides. The complete nucleotide sequence of plasmid pMG160 contained three open reading frames (ORFs). The deduced amino acid sequences encoded by ORF1 and ORF2 showed high degrees of homology to the MobS and MobL proteins that are involved in plasmid mobilization of certain plasmids. Based on homology with the Rep protein of several other plasmids, ORF3 encodes a putative rep gene initiator of plasmid replication. The functions of these sequences were demonstrated by deletion mapping, frameshift analysis, and analysis of point mutations. Two 6.1-kb pMG160-based E. coli-R. sphaeroides shuttle cloning vectors were constructed and designated pMG170 and pMG171. These two novel shuttle vectors were segregationally stable in R. sphaeroides growing under nonselective conditions.

Isolation of Rhodocyclus gelatinosus from poultry slaughterhouse wastewater

Four cultures of photosynthetic bacteria isolated from poultry slaughterhouse wastewater were identified as Rhodocyclus gelatinosus based on the following properties: reddish color of cultures in synthetic medium, presence of motility, slightly curved Gram-negative rods morphology, gelatin liquefying activity, utilization of citrate as carbon source and production of bacteriochlorophyl a and carotenoids of the spirilloxanthin alternative series. R. gelatinosus may represent a source of nutrients and pigments with application in poultry feed.

Evaluation of Rhodocyclus gelatinosus Biomass for Broiler Pigmentation

We evaluated the influence of dietary inclusion of corn gluten meal, apocarotenoic acid ethyl ester (APO-EE), canthaxanthin, and Rhodocyclus gelatinosus R1 biomass on broiler carcass color. These oxycarotenoid sources were used as pigment supplements to a basal ration containing yellow corn as the sole source of xanthophylls. Objective color values of L (lightness), C (chroma), and h (hue) were measured on skin and meat surfaces of broiler carcasses. On both surfaces, R. gelatinosus R1 biomass oxycarotenoids enhanced the chroma values (color saturation), as compared to yellow corn xanthophylls, and tended to provide yellowness to broiler carcasses, whereas the APO-EE and canthaxanthin tended to provide redness. At the concentrations studied, R. gelatinosus R1 biomass oxycarotenoids were less effective than APO-EE and canthaxanthin in enhancing color saturation. Lightness, chroma, and hue values did not differ significantly between males and females. However, skin showed significantly higher color saturation than meat in breast and thigh portions of the carcass.

Electrochemical Behavior and Nitric Oxide Interaction of Immobilized Cytochrome c′ fromRhodocyclus gelatinosus

Cytochrome c′ from Rhodocyclus gelatinosus was immobilized at a mercaptosuccinic acid modified gold electrode for the first time and the electrochemical behavior was characterized. The conditions of protein adsorption were investigated. Buffer and pH variations indicated a mainly nonionic nature of interaction. The heterogeneous electron transfer rate constant of the immobilized protein was determined (ks=30 s –1). The adsorption was found to be stable in protein-free solution for about one week. The immobilized cytochrome c′ was accessible for nitric oxide molecules in solution. The interaction resulted in an enhanced reduction current in the cyclic voltammogram. When polarized at –220 mV (vs. Ag/AgCl) the electrode current showed a linear dependence upon NO concentration. The signal was proven to be sensitive within the nanomolar range.

Ecological role of thiosulfate and sulfide utilizing purple nonsulfur bacteria of a riverine ecosystem

The screening of purple nonsulfur bacteria (PNSB) from the polluted and unpolluted zones of the river Ganga and from the discharged effluents (pollutants), revealed that the population densities of PNSB were highest in the discharged pollutants followed by polluted and unpolluted river waters in decreasing order. The allochthonous input of PNSB affected the ambient PNSB population. In all the monitored sites, the PNSB population utilizing malate as electron donor was higher than those utilizing thiosulfate or sulfide or both as electron donors. The physico-chemical parameters of the river water related to the distribution of PNSB were recorded. Twenty-four isolates of PNSB utilizing sulfide and thiosulfate, assigned to Rhodopseudomonas palustris including a morphophysiological variant of the species, Rhodobacter capsulatus and Rhodocyclus gelatinosus (= Rubrivivax gelatinosus), were screened from river Ganga. The surviving ability of PNSB population under simulated condition differed amongst the monitored sites. The isolated strains of PNSB were able to convert thiosulfate to sulfate or to elemental sulfur and also were able to oxidize sulfide. However, there was heterogeneity with respect to the rates at which they transformed these sulfur compounds. The overall thiosulfate transformation rate by the PNSB isolates in the river water was 117.3 μmol d −1 mg −1 and that of sulfide transformation was in the order of 0.15 μmol d −1 mg −1. The ecological significance of sulfide utilization in the aquatic bodies by the isolates of PNSB is discussed.

Crystal structure of cytochrome c' from Rhodocyclus gelatinosus and comparison with other cytochromes c'

Cytochromes c' are heme proteins found in photosynthetic and denitrifying bacteria, where they are presumably involved in electron transport. The cytochrome c' isolated from the bacterium Rhodocyclus gelatinosus (RGCP) forms a homodimer with each polypeptide containing 129 residues. It has been crystallised in ammonium sulfate at pH 6. Crystals belong to space group P3121 with cell parameters a = 70.2 A and c = 126.8 A, which corresponds to a dimer in the asymmetric unit (VM = 3.5 A3 / Da). The crystal structure of RGCP was solved by the molecular replacement method and refined using data to 2.5-A resolution. The final crystallographic R factor was 17.9% for all reflections (above 2 σ) in the resolution range 27.4 to 2.5 A. The refined model includes 1876 non-hydrogen protein atoms and 56 water molecules. As typical of c–type cytochromes, the heme group is covalently bound to Cys-X-Y-Cys-His through thio-ether bonds, and His123 occupies the fifth axial coordination position. On the vacant "distal" site, Phe16 blocks the direct access to the sixth coordination site, which is in a predominantly hydrophobic environment. In spite of the low sequence homology among cytochromes c' the overall fold is similar. The monomer structure consists of 4 anti-parallel α-helices and has random coils in the loops between the helices, and at the N- and C-termini. The subunits cross each other to form an X shape.

Utilization and treatment of tuna condensate by photosynthetic bacteria

Abstract

Influence of charge and polarity on the redox potentials of high-potential iron-sulfur proteins: evidence for the existence of two groups.

We have investigated the HiPIPs from Ectothiorhodospira vacuolata (iso-1 and iso-2), Chromatium vinosum, Rhodocyclus gelatinosus, Rhodocyclus tenuis (strain 2761), Rhodopila globiformis, and Rhodospirillum salinarum (iso-2) by direct electrochemistry. Using a glassy carbon electrode with a negatively charged surface, direct, unpromoted electrochemistry is possible with the positively charged HiPIPs. With the negatively charged HiPIPs, the positively charged and flexible bridging promoter poly(L-lysine) is required. The stability of the response can be improved by morpholin, aspartate, tryptophan, or 4,4'-dipyridyl. These "stabilizers" prevent the blocking of the electrode by denatured protein. The redox potential of 500 mV found for R. salinarum iso-2 is the highest HiPIP potential reported. The presence of histidines in the sequence does not per se predict a pH-dependent redox potential. Only C. vinosum and R. gelatinosus HiPIPs show a weak but significant pH dependence with a difference of 35 mV between the low- and the high-pH form and maximum slopes of -20 mV/unit. The dependence of the midpoint potential on temperature and on ionic strength varies over the different HiPIPs. The dependence of the potentials on square root of I cannot be fully explained by the Debye-Hückel theory because the linearity exceeds the limiting concentration and only small negative slopes are observed (o to -28 mV/square root of M) Combination of the sequences, the optical spectra, the overall charges, and the redox thermodynamics suggests that existence of two groups of HiPIPs. One group consists of Chromatium-like HiPIPs with redox potentials between 300 and 350 mV, modulated only by the solvation of the cluster. The second group is formed by Ectothiorhodospira-like HiPIPS with potentials between 50 and 500 mV, modulated by the overall charge of the peptide (25 mV/unit) and by the solvation of the cluster.

Primary structure and transcription of genes encoding B870 and photosynthetic reaction center apoproteins from Rubrivivax gelatinosus.

We determined the nucleotide sequence of the puf operon of Rubrivivax gelatinosus (formerly called Rhodocyclus gelatinosus), a photosynthetic bacterium belonging to the beta subclass of purple bacteria (proteobacteria). The operon contains two unknown open reading frames (ORFs) in addition to five photosynthetic genes which have been reported in species belonging to the alpha subclass. These genes include pufB, -A, -L, -M, and -C coding for the beta and alpha subunits of the B870 light-harvesting protein and for the L, M, and cytochrome subunits of the reaction center complex, respectively. One (ORF1) of the two unknown ORFs locates immediately upstream of pufB, while the other (ORF2) locates between pufB and pufA. The deduced product of ORF1 is a small basic protein composed of 41 amino acids that did not show homology with any other proteins reported to date. The deduced product of ORF2 was composed of 74 amino acids having a hydrophobic region able to span the membrane and showed homology with the beta subunit of B870. The deduced amino acid sequence of the cytochrome subunit of the reaction center of R. gelatinosus had significant deletions in the possible attachment site to the M subunit compared with that of Rhodopseudomonas viridis. This is consistent with the facilitated dissociation of this subunit observed with detergent treatment in R. gelatinosus. Analysis of RNA from R. gelatinosus showed that the puf operon of this bacterium has two transcripts; the major one is 1 kilobase in length and the minor one is 4 kilobase in length. These two transcripts have the same 5'-end, and their stoichiometry appeared to be controlled by a putative hairpin structure between pufA and pufL.

Isolation and characterisation of the core light-harvesting complex B875 and its subunit form, B820, from Rhodocyclus gelatinosus

We present a new method of preparation for Rhodocyclus gelatinosus light-harvesting complex B875 and its subunit form B820, without prior extraction of carotenoids from chromatophores. This method was based on partial dissociation of isolated B875 into B820 during hydrophobic chromatography in presence of ammonium sulphate. The two forms were then separated by gel chromatography in presence of this salt, which was required for stabilising B820. Carotenoid composition was determined for each form. B875 contained two hydroxyspheroidene molecules per bacteriochlorophyll dimer. Carotenoid content of B820 was about 5-times lower, and variable, indicating that most of this pigment was lost during the formation of B820. The apparent molecular mass of B820 antenna, determined by gel filtration, was 18–25 kDa. For B875 several values were obtained, depending on chromatographic conditions (protein and ammonium sulphate concentrations): > 600 kDa, 130 kDa and 35–40 kDa. These values may be inaccurate, because of the unknown contribution of detergent and possible interactions between the protein and the gel matrix. The results, however, indicated that B875 could present several states of aggregation, and that B820 has a smaller apparent molecular mass. Absorbance and CD spectra were measured and compared with spectra published for other species. We did not observe reconstitution of the original B875 form by increasing B820 concentration or decreasing ammonium sulphate concentration. However, another spectral form with absorbance maximum between 830–845 nm was observed, with a CD spectrum different in the infrared region from that of B820. A possible requirement of carotenoid for reassociation of B820 into B875 is discussed.

Influence of the supramolecular structure of free lipid A on its biological activity.

The three-dimensional supramolecular structures and the states of order of the acyl chains of lipid A from different Gram-negative species were investigated at 40 degrees C, high water content (80-90%), and different [lipid A]/[Mg2+] molar ratios using synchrotron radiation X-ray diffraction and Fourier-transform infrared spectroscopy. Measurements were made on free lipid A from Salmonella minnesota R595, mono- and bi-phosphoryl, as well as those from the non-enterobacterial strains Rhodobacter capsulatus 37b4, Rhodopseudomonas viridis F, and Rhodocyclus gelatinosus 29/1. Parallel to differences in their chemical primary structure, the structural polymorphisms and states of order at 37 degrees C of the non-enterobacterial lipid A were found to be different from those of enterobacterial lipid A. A clear correlation between the supramolecular structure and previously determined biological activities was found. Lipid A with a strong preference for lamellar structures (Rb. capsulatus and Rp. viridis) are endotoxically inactive and lack cytokine-inducing capacity; the compounds assuming a mixed lamellar/nonlamellar structure (monophosphoryl lipid A from S. minnesota) are of lower toxicity in vivo, but may induce cytokines in vitro; those lipid A with a strong tendency to form non-lamellar inverted structures (lipid A from S. minnesota and Rc. gelatinosus) exhibit full endotoxicity in vitro and in vivo. In contrast, anti-complementary activity is most pronounced for compounds with lamellar and least expressed for those with inverted structures. The states of order at 37 degrees C vary non-systematically, exhibiting the highest values for lipid A of S. minnesota and the lowest for that of Rc. gelatinosus. We propose to extend the term 'endotoxic conformation', which is used to describe the conformation of a single lipid A molecule required for optimal triggering of biological effects, to 'endotoxic supramolecular conformation' which denotes the particular organization of lipid A aggregates in physiological fluids causing biological activity.

Optimization for growth of Rhodocyclus gelatinosus in seafood processing effluents

Tuna condensate was a better substrate than shrimp-blanching water or effluent from a frozen-seafood plant for growing Rhodocyclus gelatinosus under anaerobic conditions in the light. One strain out of four examined, R7, gave the highest biomass (4.0 g/l), cell yield (0.32 g cell/g COD), and COD removal (78%) in 1:10 (v/v) diluted tuna condensate. Shrimp-blanching water added to the tuna condensate further increased growth rate, biomass and COD removal. Optimal growth was at pH 7.0 and 3000 Lux light intensity. Acetate, pyruvate, glucose, glutamate, propionate or malate added to the tuna condensate did not increase cell yield, carotenoid or bacteriochlorophyll content or biomass protein. A maximum cell mass of 5.6 g/l (containing 50% protein) and 86% COD removal were obtained after 5 days' incubation under optimal conditions.

The electronic structure of [Fe4S4]3+ clusters in proteins. An investigation of the oxidized high-potential iron-sulfur protein II from Ectothiorhodospira vacuolata.

Within the framework of an investigation of the electronic structure of oxidized high-potential iron-sulfur proteins (HiPIP), we have studied the HiPIP II from Ectothiorhodospira vacuolata, which was known to have a peculiar temperature dependence of the 1H NMR isotropic hyperfine shifts. The signals of the cysteine ligand protons have been sequence specifically assigned through NOE, NOESY, and TOCSY experiments. Nine hyperfine-shifted signals are observed: seven in the downfield and two in the upfield region. They have been assigned to the eight beta-CH2 protons of the four coordinated cysteines and to one alpha-CH cysteine proton. The two most downfield-shifted signals belong to the beta-CH2 protons of Cys 63 (Chromatium vinosum numbering) and the two upfield protons to those of Cys 43. These two pairs of protons show a Curie-type temperature dependence of the hyperfine shifts. Among the remaining five downfield-shifted signals, three show a Curie-type temperature dependence and two have an anti-Curie temperature dependence. The former are assigned to the beta-CH2 and alpha-CH protons of Cys 77 and the latter to the beta-CH2 protons of Cys 46. The shift patterns are thus similar, in a sequence-specific sense, to those of the analogous proteins from C. vinosum and Rhodocyclus gelatinosus, whereas they differ from those of Rhodocyclus globiformis HiPIP and even more from those of Ectothiorhodospira halophila HiPIP II. Oxidized HiPIPs can be formally viewed as containing a cluster of four ferric ions plus one extra electron. We present here a model based on a chemical equilibrium, fast on the NMR time scale, between two species, both of which contain a pair of iron(III) ions and a mixed-valence pair but are differently oriented within the protein frame. The EPR data are also discussed in the light of the debate on the nature of the different species detected at low temperature. The interpretation of the whole set of data on HiPIPs in the light of the present model is compared with that based on previous models.

Isolation, identification and growth conditions of photosynthetic bacteria found in seafood processing wastewater

Four photosynthetic bacteria, isolated from 14 samples taken from seafood processing plants, were identified as species of Rhodocyclus gelatinosus, belonging to the purple, non-sulphur bacteria of the family Rhodospirillaceae. Cultivation in synthetic medium under four different conditions indicated that all four strains gave maximum carotenoid and bacteriochlorophyll synthesis under anaerobic conditions in the light, with values of 11 to 12.6 and 102 to 108 mg/g dry cell wt, respectively. These values are 87% higher than the pigment content obtained from aerobic cultivation, although the cell biomass of all strains (1.7 to 2.3 g/l) was 22 to 38% higher under aerobic conditions. Protein content was always between 32 and 43%. The specific growth rates of all isolates in aerobic cultivation (0.04 to 0.06 h(-1)) were twice those in anaerobic conditions in the light. No growth occurred in anaerobic conditions in the dark.