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PubMed1980

Growth of Thiobacillus novellus on mixed substrates (mixotrophic growth).

In a mixotrophic environment, Thiobacillus novellus concurrently utilized glucose and thiosulfate but showed no stimulation of growth rate or yield. In most mixotrophic environments examined, the growth rate was lower than the heterotrophic growth rate, the extent of the decrease depending on the concentration and relative proportion of thiosulfate and glucose in the medium. Both thiosulfate and glucose were degraded to their most oxidized products in mixotrophic medium, yet the biomass production in this medium was comparable to that found in heterotrophic medium containing glucose alone at the corresponding concentration. It was postulated that in mixotrophic medium the oxidation of thiosulfate, glucose, or partially that of both was uncoupled from energy generation. These results differ in many respects from those reported earlier by LeJohn et al. (J. Bacteriol. 94: 1484--1491, 1967); experiments designed to exactly duplicate some of the growth conditions employed by these workers did not resolve the discrepancy.

Culture Media↗

PubMed1980

Growth and physiology of Thiobacillus novellus under nutrient-limited mixotrophic conditions.

Thiobacillus novellus was cultivated in a chemostate under the individual limitations of thiosulfate, glucose, and thiosulfate plus glucose. At dilution rate (D) of 0.05 h-1 or lower, the steady-state biomass concentration in mixotrophic medium was additive of the heterotrophic and autotrophic biomass at corresponding D values. The ambient concentrations of thiosulfate, glucose, or both in the various cultures were low and were very similar in mixotrophic, heterotrophic, and autotrophic environments at a given D value. At D = 0.05 h-1, mixotrophic cells possessed higher activities of sulfite oxidase and thiosulfate oxidation compared to autotrophic cells, as well as higher activities of glucose enzymes and glucose oxidation than heterotrophic cells. Thus, in contrast to nutrient-excess conditions, in nutrient-limited mixotrophic environments at these D values, T. novellus did not exhibit characteristics of uncoupled substrate oxidation, inhibition of substrate utilization, and repression of enzymes of energy metabolism. It is concluded that T. novellus responds to mixotrophic growth conditions differently in environments of different nutritional status, and the ecological and physiological significance of this finding is discussed.

Energy Metabolism↗

PubMed2001

Novel genes of the sox gene cluster, mutagenesis of the flavoprotein SoxF, and evidence for a general sulfur-oxidizing system in Paracoccus pantotrophus GB17.

The novel genes soxFGH were identified, completing the sox gene cluster of Paracoccus pantotrophus coding for enzymes involved in lithotrophic sulfur oxidation. The periplasmic SoxF, SoxG, and SoxH proteins were induced by thiosulfate and purified to homogeneity from the soluble fraction. soxF coded for a protein of 420 amino acids with a signal peptide containing a twin-arginine motif. SoxF was 37% identical to the flavoprotein FccB of flavocytochrome c sulfide dehydrogenase of Allochromatium vinosum. The mature SoxF (42,832 Da) contained 0.74 mol of flavin adenine dinucleotide per mol. soxG coded for a novel protein of 303 amino acids with a signal peptide containing a twin-arginine motif. The mature SoxG (29,657 Da) contained two zinc binding motifs and 0.90 atom of zinc per subunit of the homodimer. soxH coded for a periplasmic protein of 317 amino acids with a double-arginine signal peptide. The mature SoxH (32,317 Da) contained two metal binding motifs and 0.29 atom of zinc and 0.20 atom of copper per subunit of the homodimer. SoxXA, SoxYZ, SoxB, and SoxCD (C. G. Friedrich, A. Quentmeier, F. Bardischewsky, D. Rother, R. Kraft, S. Kostka, and H. Prinz, J. Bacteriol. 182:4476-4487, 2000) reconstitute a system able to perform thiosulfate-, sulfite-, sulfur-, and hydrogen sulfide-dependent cytochrome c reduction, and this system is the first described for oxidizing different inorganic sulfur compounds. SoxF slightly inhibited the rate of hydrogen sulfide oxidation but not the rate of sulfite or thiosulfate oxidation. From use of a homogenote mutant with an in-frame deletion in soxF and complementation analysis, it was evident that the soxFGH gene products were not required for lithotrophic growth with thiosulfate.

Amino Acid Sequence↗

PubMed1966

Effects of organic matter on the growth of Thiobacillus intermedius.

London, Jack (University of California, Los Angeles), and Sydney C. Rittenberg. Effects of organic matter on the growth of Thiobacillus intermedius. J. Bacteriol. 91:1062-1069. 1966.-Yeast extract, glucose, glutamate, and other organic materials stimulate the rate and extent of growth of Thiobacillus intermedius in thiosulfate broth. Growth did not occur in glucose or glutamate mineral salts medium in the absence of thiosulfate, although a stable variant was obtained which grows on yeast extract alone. Cells harvested from media supplemented with organic matter have a reduced rate of thiosulfate oxidation (20 to 30% of autotrophic), oxidize the organic supplement, and have an additive rate of oxidation in the presence of both the organic substrate and thiosulfate. Carboxydismutase synthesis is repressed, and the incorporation of bicarbonate carbon into cell material is almost completely eliminated by the presence of organic matter in the growth medium. It is concluded that the availability of organic matter eliminates the autotrophic assimilatory mechanisms of T. intermedius but not its autotrophic energy-generating system. The data are discussed in relation to the existence of "obligate" chemoautotrophic bacteria.

Bicarbonates↗

PubMed1967

Catabolite repression in the facultative chemoautotroph Thiobacillus novellus.

Several fermentable carbon sources were found to give rise to catabolite repression of all enzymes implicated in thiosulfate oxidation in the facultative chemoautotroph, Thiobacillus novellus. Glucose was found to elicit a strong repression. Glycerol, lactate, lactose, ribose, and pyruvate caused marked repression. In all cases, the repression could be relieved only by returning the cells to a medium devoid of such fermentable substrates. On the other hand, carbon compounds (amino acids and organic acids) that are metabolizable only aerobically caused transient or no repression of the thiosulfate oxidative system. All of the enzymes believed to participate in thiosulfate oxidation, except tetrathionase, were found to be simultaneously induced and repressed. This would suggest that tetrathionate may not be a necessary intermediate in the thiosulfate-oxidation pathway of T. novellus.

Cell-Free System↗

PubMed1968

Effect of thiol-binding reagents on the metabolism of Chromatium D.

Thiosulfate, intracellular sulfur, and acetate utilization by Chromatium D were inhibited by iodoacetamide, N-ethylmaleimide (NEM), p-hydroxymercuribenzoate (CMB), and HgCl(2). Pyruvate, sulfide, and sulfite utilization were insensitive to iodoacetamide, and were less sensitive to NEM, CMB, and HgCl(2) than thiosulfate, intracellular sulfur, and acetate utilization. The effect of the thiol-binding reagents on cell viability was dependent upon the method of exposure; cells exposed to the thiol-binding reagents in the presence of thiosulfate were protected from the killing action of these agents, but not from their inhibitory effect. Although the inhibitory effects of the thiol-binding reagents could, in some cases, be attributed to their effect on viability, they were inhibitory under conditions where viability was unaffected. The most straightforward results were obtained with iodoacetamide, which revealed a sharp separation in sensitivities between the systems tested but had no effect on cell viability. The results are consistent with the hypothesis that thiols are involved in thiosulfate, intracellular sulfur, and acetate utilization.

Acetates↗

PubMed1979

Efficacy of inactivators against 14 disinfectant substances.

More than 24 inactivators were tested for their suitability against 14 disinfectant substances by a quantitative suspension test. Even simple inactivators were found to be efficace: 0.1% cysteine and 0.5% sodium thiosulfate for mercuric chloride and the iodophor; 0.1% sodium sulfite for these two substances and for the QAC in the lower concentration; 1.0% polysorbate 80 for hexylresorcinol, o-phenylphenol and the QAC in the lower concentration; 0.5% sodium thioglycolate for mercuric chloride, the iodophor and chloramine-T. The inactivator active against most disinfectants was the combination LPHT or 0.3% lecithin / 3.0% polysorbate 80 /0.1% histidine / 0.5% sodium thiosulfate. Also active were: LPWT (0.5% lecithin / 1.0% polysorbate 80 /1.0% Lubrol W / 1.0% sodium thiosulfate), LPT (2.0% lecithin / 2.0% polysorbate 80 / 0.5% sodium thiosulfate) and PS (3.0% polysorbate 80 / 3.0% saponin).

Disinfectants↗

PubMedDate not supplied

[Oxidation of inorganic sulfur compounds by obligatory organotrophic bacteria].

New data obtained by the author and other researchers on two different groups of obligately heterotrophic bacteria capable of inorganic sulfur oxidation are reviewed. Among culturable marine and (halo)alkaliphilic heterotrophs oxidizing sulfur compounds (thiosulfate and, much less actively, elemental sulfur and sulfide) incompletely to tetrathionate, representatives of the gammaproteobacteria, especially from the Halomonas group, dominate. Some of denitrifying species from this group are able to carry out anaerobic oxidation of thiosulfate and sulfide using nitrogen oxides as electron acceptors. Despite the low energy output of the reaction of thiosulfate oxidation to tetrathionate, it can be utilized for ATP synthesis by some tetrathionate-producing heterotrophs; however, this potential is not always realized during their growth. Another group of marine and (halo)alkaliphilic heterotrophic bacteria capable of complete oxidation of sulfur compounds to sulfate mostly includes representatives of the alphaproteobacteria most closely related to nonsulfur purple bacteria. They can oxidize sulfide (polysulfide), thiosulfate, and elemental sulfur via sulfite to sulfate but neither produce nor oxidize tetrathionate. All of the investigated sulfate-forming heterotrophic bacteria belong to lithoheterotrophs, being able to gain additional energy from the oxidation of sulfur compounds during heterotrophic growth on organic substrates. Some doubtful cases of heterotrophic sulfur oxidation described in the literature are also discussed.

Adenosine Triphosphate↗

PubMed1990

Stable intermediates can be trapped during the reversible refolding of urea-denatured rhodanese.

The enzyme rhodanese (EC 2.8.1.1) could be reversibly refolded from urea in the presence of lauryl maltoside, beta-mercaptoethanol, and sodium thiosulfate. The unfolding/folding transition monitored using intrinsic fluorescence was resolved into two two-state transitions with midpoints at 3.6 and 5.0 M urea. The analysis assumed an intermediate with an emission maximum at 345 nm. Monitoring anisotropy of intrinsic fluorescence also gave an asymmetric transition. Activity followed one two-state transition centered at 3.6 M urea with no major change of secondary structure. Without thiosulfate or mercaptoethanol, there was one two-state transition at 5.0 M urea giving a species, in dilute urea, with a fluorescence maximum at 345 nm. This intermediate slowly relaxed toward 335 nm (t1/2 = 85 min) if only thiosulfate was absent but without regaining activity. Subsequent addition of thiosulfate led to a first-order recovery of activity (t1/2 = 75 min). Thus, a possible folding intermediate can be trapped which displays increased access of water and solutes to its fluorescent tryptophans. This intermediate conformer, which is flexible, has considerable secondary structure, is inactive, has exposed hydrophobic surfaces, and requires specific reducing conditions to regain full activity. Refolding probably involves an initial, rapid, hydrophobic collapse with acquisition of secondary structure to form the intermediate, followed by slower adjustment to the native global conformation. Final reactivation requires reduction localized at the active site.

Dithionitrobenzoic Acid↗

PubMed1975

Reduction of oxidized inorganic nitrogen compounds by a new strain of Thiobacillus denitrificans.

Denitrification by Thiobacillus denitrificans "RT" strain was investigated using manometry and gas chromatography. 1. From nitrate, resting cells produced only nitrogen anaerobically with thiosulfate as the electron donor. The data suggest that nitrate was assimilated and dissimilated by the same nitrate reductase, assayed with benzyl-viologen as the electron donor. 2. From nitrite, whole cells produced nitric oxide, nitrous oxide and nitrogen, using thiosulfate as the electron donor; nitrogen was the final product of the reduction. Crude extract reduced nitrite to nitrogen with p-phenylene-diamine and dimethyl-p-phenylene diamine as the electron donors, and produced nitric oxide, nitrous oxide and nitrogen with tetramethyl-p-phenylene-diamine as the electron donor. Nitrite was reduced to nitric oxide and nitrous oxide by crude extract using ascorbate-phenazine methosulfate as the electron donor. 3. From nitric oxide, whole cells produced nitrous oxide and nitrogen using thiosulfate as the electron donor, nitrogen was the final reduction product. Nitric oxide was reduced to nitrous oxide by crude extract with the ascorbate-phenazine methosulfate system. 4. Whole cells reduced nitrous oxide to nitrogen with thiosulfate as the electron donor. It was not possible to detect any nitrous oxide reductase activity in crude extract. 5. A scheme was of denitrification by Thiobacillus denitrificans "RT" strain.

Aerobiosis↗

PubMed1998

Hepatocyte-catalysed detoxification of cyanide by L- and D-cysteine.

The hepatocyte metabolic pathways involved in the detoxification of cyanide by cysteine have been investigated in vitro using hepatocytes isolated from Sprague-Dawley rats. Cyanide toxicity towards isolated hepatocytes could be prevented by the addition of L- or D-cysteine, cystine, or the cysteine metabolites thiosulfate and mercaptopyruvate, which markedly increased thiocyanate formation. Prior depletion of hepatocyte GSH markedly increased thiosulfate formation from L- or D-cysteine without affecting thiocyanate formation from L- or D-cysteine. This suggested that the major metabolic pathway for thiocyanate formation did not involve thiosulfate. Mercaptopyruvate was a more likely metabolic intermediate, as thiocyanate formation from L-cysteine but not thiosulfate was inhibited markedly by aminooxyacetate, a cysteine aminotransferase inhibitor, and propargylglycine, a gamma-cystathionase inhibitor. Furthermore, propargylglycine prevented L-cysteine cytoprotection against cyanide toxicity. Thiocyanate formation from D-cysteine likely also involved mercaptopyruvate, as thiocyanate formation from D-cysteine but not L-cysteine was inhibited by benzoate, an inhibitor of D-amino acid oxidase. Furthermore, benzoate prevented D-cysteine cytoprotection against cyanide toxicity. Cystine may also be an intermediate, as hepatocyte thiocyanate formation from added L-cysteine was inhibited when L-cysteine autoxidation was prevented with the copper chelator bathocuproine disulfonate. Furthermore, thiocyanate formation by rat liver homogenates with L-cystine was far more rapid than that with L-cysteine. Hepatocyte thiocyanate metabolic intermediates of beta-mercaptopyruvate and thiocystine were proposed for L-cysteine, and beta-mercaptopyruvate was proposed for D-cysteine.

Animals↗

PubMed2002

Quantification of sulfur and sulfur-containing compounds in wastewaters by means of a combination of liquid chromatographic methods.

Low-micromolar concentrations of sulfite, thiosulfate and sulfide, present in synthetic wastewater or anaerobic digester effluent, were quantified by means of derivatization with monobromobimane, followed by HPLC separation with fluorescence detection. The concentration of elemental sulfur was determined, after its extraction with chloroform from the derivatized sample. by HPLC with UV detection. Recoveries of sulfide (both matrices), and of thiosulfate and sulfite (synthetic wastewater) were between 98 and 103%. The in-run RSDs on separate derivatizations were 13 and 19% for sulfite (two tests), between 1.5 and 6.6% for thiosulfate (two tests) and between 4.1 and 7.7% for sulfide (three tests). Response factors for derivatives of sulfide and thiosulfate, but not sulfite, were steady over a 13-month period during which 730 samples were analysed. Dithionate and tetrathionate did not seem to be detectable with this method. The distinctness of the elemental sulfur and the derivatizing-agent peaks was improved considerably by detecting elution at 297 instead of 263 nm.

Calibration↗

PubMed1997

Antioxidants for prevention of methionine oxidation in recombinant monoclonal antibody HER2.

Recombinant humanized monoclonal antibody HER2, rhuMAb HER2, in liquid formulations undergoes oxidation when exposed to intense light and elevated temperatures (30 & 40 degrees C). Met-255 in the heavy chain of the Fc region of the antibody is the primary site of oxidation. Met-431 of the Fc fragment can also be oxidized under extreme conditions. The amount of oxidation was determined by cleaving the Fab and Fc fragments by papain digestion, and the oxidized Fc fragment was detected by hydrophobic interaction chromatography. Oxidation of rhuMAb HER2 was also formulation dependent. The presence of NaCl in the rhuMAb HER2 formulation caused an increase in oxidation at higher temperatures after contact with stainless steel containers or stainless steel components in the filling process. The corrosion of stainless steel by chloride ions at the low pH of the formulation buffer generated iron ions that catalyzed methionine oxidation in rhuMAb HER2. Temperature-induced oxidation of rhuMAb HER2 occurred by the formation of free radicals, and light-induced oxidation of rhuMAb HER2 occurred via single oxygen pathway. Antioxidants, such as methionine, sodium thiosulfate, catalase, or platinum, prevented Met oxidation in rhuMAb HER2, presumably as free radicals or oxygen scavengers. The minimum effective levels (molar ratios of protein to antioxidant) required to inhibit temperature-induced oxidation were 1:5 and 1:25 for methionine and thiosulfate, respectively. A thiosulfate adduct of rhuMAb HER2 was observed by cation-exchange chromatography. These studies demonstrate that stoichiometric amounts of methionine and thiosulfate are sufficient to eliminate temperature-induced oxidation of rhuMAb HER2 caused by free radicals that were generated by the presence of metal ion and peroxide impurities in the formulation.

Animals↗

PubMed2005

Synthesis of tetraoctylammonium-protected gold nanoparticles with improved stability.

This paper shows that an introduction of thiosulfate anions in place of bromide anions greatly improves both chemical and thermal stability of tetraoctylammonium-protected gold nanoparticles. Tetraoctylammonium thiosulfate [(Oct)4N+-O3SS]-protected gold nanoparticles are synthesized by the reduction of (Oct)4N+-AuCl4 to Au(I)-SSO3-, followed by the addition of sodium borohydride. The presence of thiosulfate anions instead of bromide anions on the surface of gold nanoparticles results in a significant dampening of the surface plasmon band of gold at 526 nm due to the strong interaction between thiosulfate and the gold nanoparticle surface. Cyanide decomposition and heating treatment studies suggest that (Oct)4N+-O3SS-protected nanoparticles have much higher overall stability compared to (Oct)4N+-Br-protected gold nanoparticles.

Journal Article↗

PubMed2003

Substitution reactions of [Pt(terpy)X]2+ with some biologically relevant ligands. Synthesis and crystal structure of [Pt(terpy)(cyst-S)](ClO4)2.0.5H2O and [Pt(terpy)(guo-N7)](ClO4)2.0.5guo.1.5H2O.

Substitution reactions of the complexes [Pt(terpy)(H(2)O)](2+), [Pt(terpy)(cyst-S)](2+) and [Pt(terpy)(guo-N(7))](2+), where terpy = 2,2':6',2"-terpyridine, cyst = L-cysteine and guo = guanosine, with some biologically relevant ligands such as inosine (INO), inosine-5'-monophosphate (5'-IMP), guanosine-5'-monophosphate (5'-GMP), l-cysteine, glutathione, thiourea, thiosulfate and diethyldithiocarbamate (DEDTC), were studied in aqueous 0.10 M NaClO(4) at pH 2.5 and 6.0 using variable-temperature and -pressure stopped-flow spectrophotometry. The reactions of [Pt(terpy)(H(2)O)](2+) with INO, 5'-IMP and 5'-GMP showed that these ligands are very good nucleophiles. The second order rate constants varied between 4 x 10(2) and 6 x 10(2) M(-1) s(-1) at 25 degree C. The [Pt(terpy)(cyst-S)](2+) complex is unreactive towards nitrogen donor nucleophiles, and cysteine cannot be replaced by N(7) from INO, 5'-IMP and 5'-GMP. However, sulfur donor nucleophiles such as thiourea, thiosulfate and diethyldithiocarbamate could displace the Pt-cysteine bond. Diethyldithiocarbamate is the best nucleophile and the order of reactivity is: thiourea < thiosulfate < DEDTC with rate constants of 0.936 +/- 0.002, 5.99 +/- 0.02 and 8.88 +/- 0.07 M(-1) s(-1) at 25 degree C, respectively. The reactions of [Pt(terpy)(guo-N(7))](2+) with sulfur donor ligands showed that these nucleophiles could substitute guanosine from the Pt(ii) complex, of which diethyldithiocarbamate and thiosulfate are the strongest nucleophiles. The tripeptide glutathione is also a very efficient nucleophile. Activation parameters (Delta H(++), Delta S(++) and Delta V(++)) were determined for all reactions. The crystal structures of [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O and [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O were determined by X-ray diffraction. Crystals of [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O are orthorhombic with the space group P2(1)2(1)2(1), whereas [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O crystallizes in the orthorhombic space group P2(1)2(1)2. A typical feature of terpyridine complexes can be found in both molecular structures: the Pt-N (central) bond distance, 1.982(7) and 1.92(2) A, respectively, is shorter than the other two Pt-N distances, being 2.043(7) and 2.034(7) A in [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O and 2.03(2) and 2.04(2) A in [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O, respectively. In both crystal structures two symmetrically independent cations representing different conformers are present in the asymmetric unit. The results are analysed in reference to the antitumour activity of Pt(II) complexes, and the importance of the rescue agents are discussed.

Journal Article↗

PubMed1957

The solubility and properties of a purified ichthyocol in salt solutions of neutral pH.

1. Purified citrate-extracted ichthyocol obtained from carp swim bladders has been further characterized with respect to its content of certain amino acids and carbohydrate substances. 2. The degree of solubilization or dispersion of ichthyocol by solutions of certain salts maintained in the range of neutral pH and at a temperature of 0-2 degrees C. has been determined. 3. While a number of salts of monovalent cations had no significant solubilizing effects on ichthyocol, ammonium chloride in a concentration of 1 M did cause solution of the protein. 4. Sodium thiosulfate in a range of concentrations caused the solubilization of ichthyocol but was most effective in an intermediate concentration of 0.25 M. 5. Several salts of divalent cations, in particular the chlorides of calcium, magnesium, and barium, and magnesium thiosulfate in concentrations ranging from 0.3 to 1 M caused the immediate and complete solubilization of the ichthyocol. 6. Solutions of ichthyocol in calcium chloride, magnesium chloride, and sodium thiosulfate buffered or adjusted to pH 7.0, were studied with respect to intrinsic viscosity of the protein, optical rotation, ultracentrifugal sedimentation, and reconstitution into fibers. It was found in each case that the original characteristics of the collagen, as determined previously in acid solution, were maintained when the protein was dissolved in salt solutions of neutral pH. No evidence of denaturation or gelatinization could be found when ichthyocol was solubilized under the stated conditions. 7. Collagen in neutral solution with sodium thiosulfate, calcium chloride, or magnesium chloride was not attacked by trypsin as determined viscometrically at 20.0 degrees C., but was rapidly degraded by a purified bacterial collagenase.

Acids↗

PubMed2002

Thioalkalispira microaerophila gen. nov., sp. nov., a novel lithoautotrophic, sulfur-oxidizing bacterium from a soda lake.

An anaerobic enrichment medium (pH 10) with thiosulfate as electron donor and nitrate as electron acceptor was inoculated with sediment from soda lake Fazda (Wadi Natrun, Egypt); a novel strain, ALEN 1(T), was isolated from the subsequent enrichment culture. Cells of strain ALEN 1(T) had a spiral morphology (0.3-0.45 x 1-4 microm), were motile and had a single polar flagellum. Sphaeroplasts were formed by the cells and were rapidly lysed during prolonged aerobic incubation of cultures. Cells of strain ALEN 1(T) contained a membrane-associated yellow pigment. The metabolism of this novel organism was obligately chemolithoautotrophic, and thiosulfate or sulfide were utilized as electron donors. Washed cells of strain ALEN 1(T) oxidized thiosulfate, sulfide, polysulfide and elemental sulfur to sulfate. Best growth was observed when the strain was grown under micro-oxic conditions (1-2% O2 in gas phase), whereas growth was inhibited under fully oxic conditions. Nitrate was reduced to nitrite without growth of the novel organism, but other nitrogen oxides were not utilized as electron acceptors. Strain ALEN 1(T) was alkaliphilic and moderately halophilic. It grew between pH 8 and 10.4 (optimum around pH 10) with a salt concentration of between 0.3 and 1.5 M Na+ (optimum 0-5 M). The maximum growth rate (0.08 h(-1)) of the organism was achieved in a thiosulfate-limited micro-oxic continuous culture (pH 10). Phylogenetic analyses of the 16S rDNA sequences of strain ALEN 1(T) and its closest relatives demonstrated that this strain formed a deep branch within the gamma-Proteobacteria, with no obvious association to any described cluster of species/genera. On the basis of its unique physiological properties and distinct phylogenetic position, it is proposed that strain ALEN 1(T) (= DSM 14786(T) = UNICEM 212(T)) represents a novel genus within the gamma-Proteobacteria, for which the name Thioalkalispira is proposed. It is also proposed that the type species of this novel genus be named Thioalkalispira microaerophila.

Base Sequence↗

PubMed2002

Bioenergetics of the alkaliphilic sulfate-reducing bacterium Desulfonatronovibrio hydrogenovorans.

Energy metabolism of the alkaliphilic sulfate-reducing bacterium Desulfonatronovibrio hydrogenovorans strain Z-7935 was investigated in continuous culture and in physiological experiments on washed cells. When grown in chemostats with H2 as electron donor, the cells had extrapolated growth yields [Y(max), g dry cell mass (mol electron acceptor)(-1)] of 5.5 with sulfate and 12.8 with thiosulfate. The maintenance energy coefficients were 1.9 and 1.3 mmol (g dry mass)(-1) x h(-1), and the minimum doubling times were 27 and 20 h with sulfate and thiosulfate, respectively. Cell suspensions reduced sulfate, thiosulfate, sulfite, elemental sulfur and molecular oxygen in the presence of H2. In the absence of H2, sulfite, thiosulfate and sulfur were dismutated to sulfide and sulfate. Sulfate and sulfite were only reduced in the presence of sodium ions, whereas sulfur was reduced also in the absence of Na+. Plasmolysis experiments showed that sulfate entered the cells via an electroneutral symport with Na+ ions. The presence of an electrogenic Na+-H+ antiporter was demonstrated in experiments applying monensin (an artificial electroneutral Na+-H+ antiporter) and propylbenzylylcholine mustard.HCl (a specific inhibitor of Na+-H+ antiporters). Sulfate reduction was sensitive to uncouplers (protonophores), whereas sulfite reduction was not affected. Changes in pH upon lysis of washed cells with butanol indicated that the intracellular pH was lower than the optimum pH for growth (pH 9.5). Pulses of NaCl (0.52 M) to cells incubated in the absence of Na+ did not result in ATP formation, whereas HCl pulses (shifting the pH from 9.2 to 7.0) did. Small oxygen pulses, which were reduced within a few seconds, caused a transient alkalinization. The results of preliminary experiments with chemiosmotic inhibitors provided further evidence that the alkalinization was caused by sodium--proton antiport following a primary electron-transport-driven sodium ion translocation. It is concluded that energy conservation in D. hydrogenovorans depends on a proton-translocating ATPase, whereas electron transport appears to be coupled to sodium ion translocation.

Culture Media↗