Anaerobic elemental sulfur reduction by fungus Fusarium oxysporum

Reduction of inorganic sulfur compounds by the fungus Fusarium oxysporum was examined. When transferred from a normoxic to an anoxic environment, F. oxysporum reduced elemental sulfur to hydrogen sulfide (H2S). This reaction accompanied fungal growth and oxidation of the carbon source (ethanol) to acetate. Over 2-fold more of H2S than of acetate was produced, which is the theoretical correlation for the oxidation of ethanol to acetate. NADH-dependent sulfur reductase (SR) activity was detected in cell-free extracts of the H2S-producing fungus, and was found to be up-regulated under the anaerobic conditions. On the other hands both O2 consumption by the cells and cytochrome c oxidase activity by the crude mitochondrial fractions decreased. These results indicate that H2S production involving SR was due to a novel dissimilation mechanism of F. oxysporum, and that the fungus adapts to anaerobic conditions by replacing the energy-producing mechanism of O2 respiration with sulfur reduction.     

<Emphasis Type="Italic">Desulfurispirillum alkaliphilum</Emphasis> gen. nov. sp. nov., a novel obligately anaerobic sulfur- and dissimilatory nitrate-reducing bacterium from a full-scale sulfide-removing bioreactor

Strain SR 1^T was isolated under anaerobic conditions using elemental sulfur as electron acceptor and acetate as carbon and energy source from the Thiopaq bioreactor in Eerbeek (The Netherlands), which is removing H₂S from biogas by oxidation to elemental sulfur under oxygen-limiting and moderately haloalkaline conditions. The bacterium is obligately anaerobic, using elemental sulfur, nitrate and fumarate as electron acceptors. Elemental sulfur is reduced to sulfide through intermediate polysulfide, while nitrate is dissimilatory reduced to ammonium. Furthermore, in the presence of nitrate, strain SR 1^T was able to oxidize limited amounts of sulfide to elemental sulfur during anaerobic growth with acetate. The new isolate is mesophilic and belongs to moderate haloalkaliphiles, with a pH range for growth (on acetate and nitrate) from 7.5 to 10.25 (optimum 9.0), and a salt range from 0.1 to 2.5 M Na⁺ (optimum 0.4 M). According to phylogenetic analysis, SR 1^T is a member of a deep bacterial lineage, distantly related to Chrysiogenes arsenatis (Macy et al. 1996). On the basis of the phenotypic and genetic data, the novel isolate is placed into a new genus and species, Desulfurispirillum alkaliphilum (type strain SR^T = DSM 18275 = UNIQEM U250). Nucleotide sequence accession number: the GenBank/EMBL accession number of the 16S rRNA gene sequence of strain SR 1^T is DQ666683.     

化能自养硫氧化细菌Halothiobacillus sp.LS2介导的以乙炔为电子受体的硫氧化反应

【目的】探究化能自养硫氧化细菌Halothiobacillus sp. LS2介导的以乙炔为电子受体的厌氧硫氧化反应。【方法】稀释涂布法测定细胞生长情况,离子色谱仪测试硫氧化动力学中SO_4~(2–)和S_2O_3~(2–)以及基于相对荧光定量法的基因表达分析。【结果】尽管菌株LS2在以氧气为电子受体时的最大反应速率V_(max)更高,但在厌氧条件下且以乙炔为电子受体时,菌株LS2的生长量是氧气为电子受体时的2倍,且硫氧化酶基因soxB的表达量显著高于氧气作为电子受体时。【结论】菌株LS2不仅可以以乙炔为电子受体完成厌氧硫氧化反应,且这一代谢过程的产能效率较有氧硫氧化过程更高。本研究首次发现了微生物介导的以乙炔为电子受体的厌氧硫氧化反应,对丰富硫的生物地球化学循环理论有积极意义。     

Oxidation of H2, organic compounds and inorganic sulfur compounds coupled to reduction of O2 or nitrate by sulfate-reducing bacteria

All of fourteen sulfate-reducing bacteria tested were able to carry out aerobic respiration with at least one of the following electron donors: H₂, lactate, pyruvate, formate, acetate, butyrate, ethanol, sulfide, thiosulfate, sulfite. Generally, we did not obtain growth with O₂ as electron acceptor. The bacteria were microaerophilic, since the respiration rates increased with decreasing O₂ concentrations or ceased after repeated O₂ additions. The amounts of O₂ consumed indicated that the organic substrates were oxidized incompletely to acetate; only Desulfobacter postgatei oxidized acetate with O₂ completely to CO₂. Many of the strains oxidized sulfite (completely to sulfate) or sulfide (incompletely, except Desulfobulbus propionicus); thiosulfate was oxidized only by strains of Desulfovibrio desulfuricans; trithionate and tetrathionate were not oxidized by any of the strains. With Desulfovibrio desulfuricans CSN and Desulfobulbus propionicus the oxidation of inorganic sulfur compounds was characterized in detail. D. desulfuricans formed sulfate during oxidation of sulfite, thiosulfate or elemental sulfur prepared from polysulfide. D. propionicus oxidized sulfite and sulfide to sulfate, and elemental sulfur mainly to thiosulfate. A novel pathway that couples the sulfur and nitrogen cycles was detected: D. desulfuricans and (only with nitrite) D. propionicus were able to completely oxidize sulfide coupled to the reduction of nitrate or nitrite to ammonia. Cell-free extracts of both strains did not oxidize sulfide or thiosulfate, but formed ATP during oxidation of sulfite (37 nmol per 100 nmol sulfite). This, and the effects of AMP, pyrophosphate and molybdate on sulfite oxidation, suggested that sulfate is formed via the (reversed) sulfate activation pathway (involving APS reductase and ATP sulfurylase). Thiosulfate oxidation with O₂ probably required a reductive first step, since it was obtained only with energized intact cells.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - APS adenosine phosphosulfate or adenylyl sulfate     

兼性厌氧细菌硫化氢的产生机理及其生理功能

硫化氢(H_2S)是继一氧化氮(NO)和一氧化碳(CO)后发现的第3种气态信号分子,但其细菌生理学研究才刚刚起步。本文根据作者对奥内达希瓦氏菌的研究,结合新近文献,就细菌的H_2S产生机理及其生理功能作了较为全面的阐述。细菌的H_2S产生途径主要有2条,一是通过降解半胱氨酸产生,二是通过厌氧呼吸产生。产生的H_2S除可为互生性微生物提供能源、供氢体和无机矿质营养外,还具有抑制竞争性微生物的生长,有效占领生态位的作用。H_2S在氧化应答中也起着重要的作用,一方面可抑制过氧化氢酶活性,增加过氧化氢对细菌的杀灭效果;另一方面可作为信号分子激活细菌的氧化应答,诱导拮抗系统的表达,保护细胞免受氧化损伤。这两种看似"矛盾"的作用与H_2S的处理时间有关:短时间处理以抑制为主,而延长处理时间则以保护为主。细菌H_2S产生机理及生理功能的阐明可为硫元素生物地球化学循环规律的揭示和感染性病原细菌的控制提供有益的参考。     

Drugs with susceptible sites for free radical induced oxidative transformations: the case of a penicillin

Penicillins, as bactericidal antibiotics, have been widely used to treat infections for several decades. Their structure contains both aromatic and thioether moieties susceptible to free radical oxidation. The ^?OH induced oxidation mechanism of amoxicillin was investigated by pulse radiolysis techniques and by final product analysis performed after steady-state γ-irradiation. The predominant sites of the ^?OH attack are suggested to be the thioether group, initially yielding an ^?OH adduct to the sulfur, and the aromatic ring. This adduct to the sulfur converts to sulfur radical cation, which has three competitive reaction paths: (1) by deprotonation at the adjacent carbon α-(alkylthio)alkyl radicals form, which undergo disproportionation leading presumably to sulfoxide as main product; (2) via the pseudo-Kolbe mechanism it may transform to α-aminoalkyl radicals; (3) the radical cation can be stabilized through intramolecular S.˙.O bond formation. The reaction mechanism suggests the presence of a short-living and a stabilized (via hydrogen bonding) long-living ^?OH adduct to the sulfur. The three-electron bonded dimers of amoxicillin were not formed owing to steric hindrance. Thiyl radicals were also present in equilibrium with α-aminoalkyl radicals. In the presence of dissolved oxygen, aromatic ring hydroxylation occurred along with complex reactions resulting in e.g. oxidation of the methyl groups. The formation of the sulfoxide is especially effective in the presence of dissolved oxygen, under anaerobic condition, however, it is also generated owing to H₂O₂ and α-(alkylthio)alkyl radicals. The thioether moiety appears to be more sensitive to oxidation compared to the aromatic ring in case of amoxicillin.     

Stetteria hydrogenophila, gen. nov. and sp. nov., a novel mixotrophic sulfur-dependent crenarchaeote isolated from Milos, Greece

A new hyperthermophilic, strictly anaerobic crenarchaeote, Stetteria hydrogenophila DSM11227 representing a new genus within the family of Desulfurococcaceae, was isolated from the sediment of a marine hydrothermal system at Paleohori Bay in Milos, Greece. Cells are gram-negative irregular and disc-shaped cocci, 0.5–1.5 μm in diameter, which are flagellate and can form cytoplasmatic protrusions up to 2 μm in length. The strain grew optimally at 95°C at pH 6.0 and at a NaCl concentration of 3%. The organism grew mixotrophically on peptide substrates. It required elemental sulfur as an external electron acceptor, and in addition, its growth was completely dependent on the presence of molecular hydrogen. Sulfur could be replaced by thiosulfate. H₂S, CO₂, acetate, and ethanol were identified as products of metabolism. The G + C content of DNA was 65 mol%. Analysis of its phylogenetic position by sequence analysis of 16S rRNA placed this organism in the family of Desulfurococcaceae. The dependence of this organism on both hydrogen and sulfur during growth on peptide substrates distinguishes Stetteria from all previously described species of Crenarchaeota. Received: September 4, 1996 / Accepted: November 12, 1996     

Mechanism of acetate oxidation to CO2 with elemental sulfur in Desulfuromonas acetoxidans

The strict anaerobe Desulfuromonas acetoxidans can oxidize acetate to CO₂ with elemental sulfur as electron acceptor. ¹⁴C-labelling experiments and enzyme studies are described revealing that acetate oxidation proceeds via the citric acid cycle with the synthesis of oxaloacetate from acetate and 2 CO₂ via pyruvate as anaplerotic reaction. An oxidation of acetate via one carbon unit intermediates as proposed for anaerobic bacteria fermenting acetate to 2 CO₂ and 4 H₂ was excluded.Dedicated to Professor Dr. Gerhart Drews on the occasion of his 60th birthday     

Oxidation of organic compounds to CO2 with sulfur or thiosulfate as electron acceptor in the anaerobic hyperthermophilic archaea Thermoproteus tenax and Pyrobaculum islandicum proceeds via the citric acid cycle

The oxidation of organic compounds with elemental sulfur or thiosulfate as electron acceptor was studied in the anaerobic hyperthermophilic archaea Thermoproteus tenax and Pyrobaculum islandicum. T. tenax was grown on either glucose or casamino acids and sulfur; P. islandicum on peptone and either elemental sulfur or thiosulfate as electron acceptor. During exponential growth only CO₂ and H₂S rather than acetate, alanine, lactate, and succinate were detected as fermentation products of both organisms; the ratio of CO₂/H₂S formed was 1:2 with elemental sulfur and 1:1 with thiosulfate as electron acceptor. Cell extracts of T. tenax and P. islandicum contained all enzymes of the citric acid cycle in catabolic activities: citrate synthase, aconitase, isocitrate dehydrogenase (NADP⁺-reducing), oxoglutarate: benzylviologen oxidoreductase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase and malate dehydrogenase (NAD⁺-reducing). Carbon monoxide dehydrogenase activity was not detected. We conclude that in T. tenax and P. islandicum organic compounds are completely oxidized to CO₂ with sulfur or thiosulfate as electron acceptor and that acetyl-CoA oxidation to CO₂ proceeds via the citric acid cycle.     

Alcohol conversion by Desulfobulbus propionicus Lindhorst in the presence and absence of sulfate and hydrogen

Ethanol was rapidly degraded to mainly acetate in anaerobic freshwater sediment slurries. Propionate was produced in small amounts. Desulfovibrio species were the dominant bacteria among the ethanol-degrading organisms. The propionate-producing Desulfobulbus propionicus came to the fore under iron-limited conditions in an ethanol-limited chemostat with excess sulfate inoculated with anaerobic intertidal freshwater sediment. In the absence of sulfate, ethanol was fermented by D. propionicus Lindhorst to propionate and acetate in a molar ratio of 2.0.l-Propanol was intermediately produced during the fermentation of ethanol. In the presence of H₂ and CO₂, ethanol was quantitatively converted to propionate. H₂-plus sulfate-grown cells of D. propionicus Lindhorst were able to oxidize l-propanol and l-butanol to propionate and butyrate respectively with the concomitant reduction of acetate plus CO₂ to propionate. Growth was also observed on acetate alone in the presence of H₂ and CO₂ D. propionicus was able to grow mixotrophically on H₂ plus an organic compound. Finally, a brief discussion has been given of the ecological niche of D. propionicus in anaerobic freshwater sediments.     

34S/32S and 18O/16O Fractionation During Sulfur Disproportionation by Desulfobulbus propionicus

In the present study, coupled stable sulfur and oxygen isotope fractionation during elemental sulfur disproportionation according to the overall reaction: 4H₂O + 4S^? → 3H₂S + SO₄ ^{2 ?} + 2H⁺, was experimentally investigated for the first time using a pure culture of the sulfate reducer Desulfobulbus propionicus at 35^?C. Bacterial disproportionation of elemental sulfur is an important process in the sulfur cycle of natural surface sediments and leads to the simultaneous formation of sulfide and sulfate. A dual-isotope approach considering both sulfur and oxygen isotope discrimination has been shown to be most effective in evaluating specific microbial reactions. The influence of iron- and manganese bearing-solids (Fe(II)CO₃, Fe(III)OOH, Mn(IV)O₂) acting in natural sediments as scavengers for hydrogen sulfide, was considered, too. Disproportionation of elemental sulfur was observed in the presence of iron solids at a cell-specific sulfur disproportionation rate of about 10^{? 9.5± 0.4} μ mol S^? cell^{? 1} h^{? 1}. No disproportionation, however, was observed with MnO₂. In the presence of iron solids, newly formed sulfate was enriched in ¹⁸ O compared to water by about +21‰ (≡ ? _H2O ), in agreement with a suggested oxygen isotope exchange via traces of intra- or extracellular sulfite that is formed as a disproportionation intermediate. Dissolved sulfate was also enriched in ³⁴S compared to elemental sulfur by up to +35%. Isotope fractionation by Desulfobulbus propionicusis highest for all disproportionating bacteria investigated, so far, and may impact on the development of isotope signals at the redox boundary of surface sediments.     

Desulfuromonas acetoxidans gen. nov. and sp. nov., a new anaerobic,sulfur-reducing,acetate-oxidizing bacterium

Anaerobic sea or fresh water media with acetate and elemental sulfur yielded enrichments of a new type of strictly anaerobic, rod-shaped, laterally flagellated, Gram-negative bacterium. Three pure culture-strains from different sulfide-containing sea water sources were characterized in detail and are described as a new genus and species Desulfuromonas acetoxidans.The new bacterium is unable to ferment organic substances; it obtains energy for growth by anaerobic sulfur respiration. Acetate, ethanol or propanol can serve as carbon and energy source for growth; their oxidation to CO₂ is stoichiometrically linked to the reduction of elemental sulfur to sulfide. Organic disulfide compounds, malate or fumarate are the only other electron acceptors used. Butanol and pyruvate are used in the presence of malate only; no other organic compounds are utilized. Biotin is required as a growth factor. The following dry weight yields per mole of substrate are obtained: in the presence of sulfur: 4.21 g on acetate, 9.77 g on ethanol; in the presence of malate: 16.5 g on acetate, 34.2 g on ethanol and 46.2 g on pyruvate. Accumulations of cells are pink; cell suspensions exhibit absorption spectra resembling those of c-type cytochromes (abs. max. at 419, 523 and 553 nm). Malate-ethanol grown cells contain a b-type cytochrome in addition.In the presence of acetate, ethanol or propanol, Desulfuromonas strains form robust growing syntrophic mixed cultures with phototrophic green sulfur bacteria.Dedicated to Prof. Roger Y. Stanier on the occasion of his 60th barthday     

Impact of Atmospheric Sulfur Deposition on Sulfur Metabolism in Plants: H2S as Sulfur Source for Sulfur Deprived Brassica oleracea L.

Brassica oleracea L. was rather insensitive to atmospheric H₂S: growth was only negatively affected at ≥0.4 μl I^?1. Shoots formed a sink for H₂S and the uptake rate showed saturation kinetics with respect to the atmospheric concentration. The H₂S uptake rate was high in comparison with other species, which may reflect the high sulfur need of Brassica. The net uptake of sulfate by roots of hydroponically grown plants was substantially reduced after one week of exposure to 0.25 μl l^?1 H₂S, indicating that plants switched in part from sulfate to H₂S as sulfur source for plant growth. Plants were sulfur deficient after two weeks of sulfur deprivation, illustrated by reduced growth, which was more pronounced for shoots than for roots, and in enhanced shoot dry matter content. The latter could for the greater part be attributed to enhanced levels of soluble sugars and starch. Sulfur deficiency was further characterized by a low pigment content, extremely low levels of sulfate and water-soluble non-protein thiols, and by enhanced levels of nitrate and free amino acids, particularly in the shoots. Furthermore, sulfur deficient plants contained a lower total lipid content in shoots, whereas its content in roots was unaffected. The level of sulfolipids was decreased in both roots and shoots. When sulfur deprived plants were exposed to 0.25 μl I^?1 H₂S for one week, all sulfur deficiency symptoms were abolished and growth was restored. Furthermore, plants were able to grow with 0.4 μl I^?1 H₂S as the sole sulfur source. Water-soluble non-protein thiol content was enhanced in both shoots and roots of H₂S exposed plants, irrespective of the sulfate supply to the roots, whereas plants grown with H₂S as sole sulfur source contained very low sulfate levels. The interaction between atmospheric and pedospheric sulfur nutrition in plants is discussed.     

Role of sulfate in detoxification of arsenate-induced toxicity in Zea mays L. (SRHM 445): nutrient status and antioxidants

The study highlights the role of sulfur (S) in detoxification of arsenate-induced toxicity and the shift in essential element homeostasis in Zea mays L (SRHM 445). Overall growth of arsenate-treated plants under sulfur starvation (?S) was lower than that in the presence of excess sulfur (+S). Translocation of arsenate from roots to shoots, increased under As(?S) and decreased with As(+S). The level of micronutrients (Cu, Zn, Fe) increased in As(?S) plants. Whereas, the level of K and PO₄ was higher in As(?S) plants than in As(+S) plants. Higher malondialdehyde, protein carbonyl, and H₂O₂ levels in As(?S) plants are indicative of higher oxidative stress. Higher superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities, in As(?S) plants coincided with higher H₂O₂ levels showing the activity of these enzymes are independent of S availability. Absence of reduced glutathione/oxidized glutathione pool in (?S) plants manifested into failure of ascorbate–glutathione detoxification pathway. Hence, S has dual role of protecting the plant against arsenate-induced toxicity (1) by restricting arsenic (As) translocation to the upper parts and (2) by increasing the activity SOD and APX.     

Formation of dimethylsulfide and methanethiol from methoxylated aromatic compounds and inorganic sulfide by newly isolated anaerobic bacteria

Formation of gas and of methylated sulfur compounds was observed in anaerobic enrichment cultures with methoxylated aromatic compounds as substrates. Via direct dilution of mud samples in defined reduced media supplemented with trimethoxybenzoate or syringate two new strains of anaerobic homoacetogenic bacteria (strain TMBS4 and strain SA2) were obtained in pure culture. Both strains produced dimethylsulfide and methanethiol during growth on methoxylated aromatic compounds. Growth tests and determination of stoichiometries demonstrated that the volatile sulfur compounds were formed from the methyl group at the aromatic ring and the sulfide added as reducing agent to the medium (R = aromatic residue): 2 R - O - CH₃ + H₂ S 2 R - OH + (CH₃)₂SDimethylsulfide was the major organic sulfur compound formed, whereas methanethiol appeared only as intermediate in small quantities. The isolates grew also with trihydroxybenzenes such as gallate, phloroglucinol, or pyrogallol without formation of methylated sulfur compounds. The aromatic compounds were degraded to acetate. The freshwater strain TMBS4 also fermented pyruvate. Other aliphatic or aromatic compounds were not utilized. External electron acceptors (sulfate, nitrate, fumarate) were not reduced. Both strains were mesophilic and formed rod-shaped, non-motile, Gram-negative cells. Spore formation was not observed. Tentatively, both isolates can be affiliated to the genus Pelobacter.Abbreviations TMB 3,4,5-trimethoxybenzoate - MT methanethiol - DMS dimethylsulfide     

Control of Oxidative Sulfur Metabolism of Chlorobium limicola forma thiosulfatophilum

A metered blend of anaerobic-grade N₂, CO₂, and H₂S gases was introduced into an illuminated, 800-ml liquid volume, continuously stirred tank reactor. The system, described as an anaerobic gas-to-liquid phase fed-batch reactor, was used to investigate the effects of H₂S flow rate and light energy on the accumulation of oxidized sulfur compounds formed by the photoautotroph Chlorobium limicola forma thiosulfatophilum during growth. Elemental sulfur was formed and accumulated in stoichiometric quantities when light energy and H₂S molar flow rate levels were optimally adjusted in the presence of nonlimiting CO₂. Deviation from the optimal H₂S and light energy levels resulted in either oxidation of sulfur or complete inhibition of sulfide oxidation. Based on these observations, a model of sulfide and sulfur oxidases electrochemically coupled to the photosynthetic reaction center of Chlorobium spp. is presented. The dynamic deregulation of oxidative pathways may be a mechanism for supplying the photosynthetic reaction center with a continuous source of electrons during periods of varying light and substrate availability, as in pond ecosystems where Chlorobium spp. are found. Possible applications for a sulfide gas removal process are discussed.     

Investigations on microbial sulfur respiration

The reduction of elemental or sulfane sulfur to hydrogen sulfide by eubacteria was investigated. Spirillum 5175 had the most active sulfur oxidoreductase. It could be cultivated with fumarate (F), elemental sulfur (S) or nitrate (N) as electron acceptor. Maximum activity was found for Spirillum 5175_S but activity was also present in Spirillum 5175_F and Spirillum 5175_N, i.e. the sulfur oxidoreductase is a constitutive enzyme. It was localized in the membrane, and no activity was found in the cytoplasm in contrast to Desulfovibrio baculatus. Different procedures were applied for the measurement of the sulfur oxidoreductase activity. In the manometric assay hydrogenase was coupled to the sulfur oxidoreductase, and the uptake of dihydrogen was measured in the presence of elemental sulfur. Alternatively, H₂S was assayed directly or was trapped in 12% NaOH and determined by the methylene blue procedure. Using ³⁵S sulfur and ³⁵S-labelled compounds both the substrate and H₂S could be measured. A further increase in sensitivity was achieved using phenosafranin. It was reduced photochemically, and served as the electron donor to the sulfur oxidoreductase, i.e. no hydrogenase was required. This was an important result in view of the fact that not all sulfur-reducing bacteria contain hydrogenase. However, in those cases the hydrogenase isolated from Clostridium pasteurianum could be coupled to the sulfur oxidoreductase. Among the different forms of elemental sulfur Janek sulfur gave the best results in terms of activity and reproducibility. The reduction of elemental sulfur to hydrogen sulfide had a pH optimum at pH 8.7–8.9. There was always a lag-phase which was pH-dependent. During this period the turbidity of the solution changed. Addition of thiols, such as GSH, shortened the lag-phase and caused an increase in activity of the sulfur oxidoreductase. In the presence of p-chloromercuribenzenesulfonic acid the reaction rate decreased significantly. Comparable reaction rates and activity values of the sulfur oxidoreductase in Spirillum 5175_F were obtained with organic trisulfides, RS-S-SR. In contrast to elemental sulfur RS-S-SR are well-defined chemical compounds suitable for quantitative and mechanistic investigations. Labelling the central sulfur of RS-S-SR with ³⁵S gave a satisfactory recovery of the total radioactivity in form of (³⁵S) H₂S in our assay. Trisulfides were shown to be formed as reactive intermediates in bacteria. This process required the sulfur transferase rhodanese which was present in Spirillum 5175, or other sulfur-reducing eubacteria.Abbreviations EPR Electron Paramagnetic Resonance - A Absorbance - PCMS p-chloromercuribenzenesulfonic acid - Sp. 5175_F Splrillum 5175 grown with fumarate - Sp. 5175_S with sulfur - Sp. 5175_N with nitrate - SCE Standard Calomel Electrode     

深海热液生物共附生可培养硫氧化细菌的多样性及硫氧化特性

[背景]深海热液环境中存在大量H2S及含硫化合物,许多微生物与大型生物形成了紧密的共生体系,例如硫氧化细菌,它们利用其独特的代谢体系协助宿主更好地适应极端环境,但目前尚未对热液底栖生物共附生的硫氧化细菌进行培养鉴定和功能分析.[目的]了解深海热液生物共附生硫氧化细菌的种群特征和功能特征,筛选出深海热液生物共附生微生物中...