Kinetics of SO4−2 reduction under different growth media by sulfate reducing bacteria

Sulfate Reducing Bacteria (SRB) were used to reduce the SO₄ ^–2 concentration in waste water. The growth pattern of SRB was found by varying the concentration of nutrients and the biomass. The specific reaction constant was evaluated in each case.     

Inhibitory effects of enterococci on the production of hydrogen sulfide by hydrogen sulfide-producing bacteria in raw meat

Aims: Applying competitive exclusion micro‐organisms to control hydrogen sulfide (H₂S) gas produced by hydrogen sulfide–producing bacteria (SPB) in chicken meat. Methods and Results: Five SPB strains, isolated from animal by‐products, were used for screening lactic acid bacteria (LAB) that can inhibit the production of H₂S by SPB in trypticase soy broth supplemented with l ‐cysteine (TSB‐l ‐cys). A sensitive and accurate test strip method was developed for H₂S determination in real time. One LAB strain, isolate L86, from cheese whey, demonstrated the highest inhibitory activity against the production of H₂S by SPB. The isolate L86 was confirmed as Enterococcus faecium that does not possess genes encoding for vancomycin resistance based on PCR analysis. Enterococcus faecium strain L86 reduced (P < 0·05) the yield of H₂S upto 51·2% in 10 h at 35°C in TSB‐l ‐cys medium. In fresh chicken meat, the yield of H₂S produced by the artificially inoculated SPB was reduced (P < 0·05) by 48·6, 49·7 and 69·8% in 10 h at 35, 30 and 25°C, respectively. Enterococcus faecium strain L86 also reduced (P < 0·05) by 53·8% on the yield of H₂S produced by the indigenous SPB in partially spoiled chicken meat at 35°C for 10 h. Conclusions: Enterococcus faecium strain L86 is effective on inhibiting the production of H₂S by SPB. Significance and Impact of the Study: The application of this biological agent to raw animal by‐products will provide a safer working environment in rendering processing plants and produce higher‐quality rendered products.     

硫酸盐还原菌固态发酵产品酶活测定方法的建立

为建立生物质固载硫酸盐还原菌（SRB）产品酶活的检测方法,首先确定亚硫酸盐还原酶（SiR）作为SRB胞外酶表征其生物活性的可行性;其次对固态发酵产品制备粗酶液的各种条件进行探讨,研究浸泡介质、浸泡时间、超声功率、超声时间、预处理方式等单因素对酶活的影响;由正交实验确定粗酶液制备的最佳工况。实验结果表明,先浸提后超声处理的酶活值显著高于仅用超声、浸提的结果。为确保酶活值测定不受干扰,排除超声温度对结果的影响,确定实验最佳工况：2g固态发酵产品经磷酸盐缓冲液25mL、浸提60min,酶活值为1．0799U／g。生物质固载SRB酶活检测方法的建立为固态发酵产品活性评价、固态发酵条件优化、可渗透反应墙生化性能评估提供一定的理论依据。     

水稻土中硫酸盐还原微生物研究进展

硫是水稻必需的营养元素之一.硫酸盐还原是硫元素生物地球化学循环中的关键步骤,在稻田土壤表层和水稻根际都十分活跃.介导硫酸盐还原过程的硫酸盐还原菌(sulfate- reducing bacteria, SRB)是稻田土壤中重要的功能菌群.它们不仅是硫元素生物地球化学循环的重要参与者,也是土壤中有机污染物降解的主要力量之一,发挥着重要的生态和环境功能.综述了稻田土壤中微生物参与的硫酸盐还原过程、SRB的生物多样性以及目前研究稻田土壤SRB主要采用的分子生态学方法,如末端限制性片段长度多样性(T-RFLP)、变性梯度凝胶电泳(DGGE)、实时荧光定量PCR(real-time PCR)、荧光原位杂交(FISH),并对水稻土壤中SRB的分子生态学研究方向进行了展望.     

Phylogenetic studies of two rubredoxins from sulfate reducing bacteria

Summary The sequences of two rubredoxins isolated from the sulfate reducing bacteria:Desulfovibrio vulgaris andDesulfovibrio gigas have been elucidated. They have similar sequences but many more differences occur than would be expected from two bacteria of the same genus. Of the 52 sites, only 37 are occupied by identical residues. The primary structures are compared with those of the anaerobic bacteria rubredoxins ofClostridium pasteurianum, Micrococcus aerogenes, Pseudomonas oleovorans andPeptostreptococcus elsdenii: only 12 identities are found, mostly in the two clusters that contain two iron-bound cysteines each. A phylogenetic tree based on the primary structures is presented and possible relations with plant and bacterial ferredoxins are discussed. A secondary and tertiary structure, stereochemically compatible with the sequence data, is proposed.To whom reprint requests should be addressed     

Electrochemical identification of microbially mediated hydrogen sulfide oxidation

The process of H₂S oxidation by the phototrophic bacteriaThiocapsa roseopersicina andChlorobium phaeobacteroides, respectively, was monitored using a Pt-glass-Ag⁰, Ag₂S electrode combination without liquid junction. Due to the resulting pe(pH) and pH₂S plottings three steps can be distinguished: oxidation of H₂S to an S(0) state, oxidation of S (0) to SO₄ ^2–, and oxidation of the remaining H₂S directly to SO₄ ^2–. Differences between the investigated bacteria exist with respect to their individual oxidation strategies.Thiocapsa apparently stops oxidizing H₂S at pH₂S 7.5 (e.g. 10^–7.5M H₂S) and shifts to the utilization of the intracellularly stored S (0). In contrastChlorobium utilizes its extracellularly stored sulfur parallel to the extracellular H₂S fraction. The corresponding Pt-sensor responses (pe₇ values) were found to be similar to the corresponding partial redox equilibria (p₇ values) of H₂S oxidation stoichiometries as proposed by Van Niel (1931) and Trüper (1964). It is concluded that the recording of pe enables investigators to understand (and control) in situ redox processes, independent of their thermodynamic equilibration, only bound to changes of electroactivity vs. sensor.     

Hydrolysis of newspaper polysaccharides under sulfate reducing and methane producing conditions

The initial decomposition rates of cellulose and hemicellulose were measured using toluene to specifically inhibit the microbial uptake of hydrolysis products during the degradation of newspaper under sulfate reducing and methane producing conditions. The amount of glucose and xylose accumulation in the first 2 weeks of incubation period was higher in the sulfate reducing condition compared to the methane producing condition. It was estimated that 28 and 6% of initially loaded cellulose in the sulfate reducing condition and the methane producing condition was hydrolyzed, respectively. Accordingly, the newspaper-cellulose hydrolysis rate constant was estimated to be 6.7 times higher in sulfate reducing condition than in methane producing condition. Based on the glucose accumulation patterns, when sulfate reducing bacteria (SRB) were inhibited by anthraquinone and molybdate (Na₂MoO₄), it may be suggested that SRB might have contributed to the hydrolysis of cellulose, while their effect on the hydrolysis of hemicellulose could not be elucidated.     

Inhibition of methanogenesis by sulphate reducing bacteria competing for transferred hydrogen

A methanogenic bacterial consortium was obtained after inoculation of benzoate medium under N₂/CO₂ atmosphere with intertidal sediment. A hydrogen donating organotroph andMethanococcus mazei were isolated from this enrichment. H₂-utilising sulphate reducing bacteria were isolated under H₂/CO₂ in the absence of organic electron donors. TheMethanococcus was able to produce methane in yeast extract medium under N₂/CO₂ if the H₂ donating organism was present, and sulphate reduction occurred if the hydrogen utilising sulphate reducing bacteria were grown with the H₂ donating organism. The ability of the H₂ utilising sulphate reducing bacteria to inhibitMethanococcus competitively was shown in cultures containing both of these H₂ utilising bacteria.Abbreviations HDO hydrogen donating organism - SRB sulphate reducing bacteria - HSRB hydrogen utilising sulphate reducing bacteria     

硫化氢抗大鼠动脉粥样硬化作用研究

目的:探讨硫化氢(H2S)对大鼠动脉粥样硬化(AS)的作用及其机制。方法:体重(210±10)g的健康雄性SD大鼠125只,随机分为:对照组、AS模型组、AS+低剂量NaHS(2.8μmol/(kg.d))组、AS+中剂量NaHS(14μmol/(kg.d))组及AS+高剂量NaHS(28μmol/(kg.d))组。采用高脂饲料加大剂量VitD3注射复制大鼠AS模型。NaHS腹腔注射,连续用药12周。分别在喂养前及喂养后3、6、9、12周各处死动物。用生化分析仪检测血脂,去蛋白法检测血浆硫化氢,HE染色观察血管病理损伤程度及病变评分,免疫组化法检测血管组织中血管内皮生长因子(VEGF)的表达。结果:与相同时期的对照组相比,AS模型组在喂养后3、6、9、12周,血清甘油三脂(TG)和胆固醇(TC)均明显升高;主动脉病变评分从第6周到12周明显增加(P0.01),并出现明显的动脉粥样硬化病变,表现为阳性区域的脂质斑块;血清H2S浓度明显降低,从喂养前的(44.98±2.06)μmol/L到第3、6、9、12周分别为(38.56±2.26),(32.96±2.38),(28.63±0.92),(23.55±0.92)μmol/L,并分别低于同时期各对照组的(44.72±0.85),(43.71±0.59),(41.96±0.97),(39.87±1.25)μmol/L(P0.01);血管组织中VEGF的表达明显增强(P0.01)。与模型组比较,低剂量NaHS组,各指标均无明显变化;中剂量NaHS组大鼠血清H2S含量于第6周开始明显高于模型组(36.13±0.73)vs(32.96±2.38)μmol/L,P0.05;于9、12周时,分别为(33.07±1.14)vs(28.63±0.92)μmol/L,(30.16±0.62)vs(23.55±0.92)μmol/L,P0.01;高剂量NaHS组大鼠血中H2S浓度于第3周开始到12周,分别为:(41.25±0.80),(38.71±0.46),(35.31±0.62),(33.38±0.78)μmol/L,均明显高于模型组(P0.01);中、高剂量NaHS组血清TC均从第3周开始到12周明显降低(P0.01),TG分别从第3、第6周开始到12周明显降低(P0.05,P0.01),血管组织病变评分与VEGF的表达均于第6周开始到12周明显降低(P0.05)。相关分析显示血清中硫化氢的浓度与动脉粥样硬化的病变评分及血管VEGF的表达呈明显的负相关(r=-0.917,P0.01,r=-0.885,P0.01),而与血清甘油三脂和胆固醇之间无显著相关性。结论:动脉粥样硬化病变的形成与发展与内源性硫化氢的降低密切相关,补充外源性H2S可提高动脉粥样硬化大鼠血清中硫化氢浓度,减轻血管损伤程度,抑制VEGF的表达。     

Localization of sulfate reduction in planted and unplanted rice field soil

Rates of in situ sulfate reduction (SRR) in planted and unplanted rice fieldsoil were measured by the ³⁵SO^2– ₄-radiotracermethod using soil microcosms. The concentration of ³⁵SO^2– ₄ decreased exponentially with time.However, time course experiments indicated that incubation times of10–30 min were appropriate for measurements of SRRusing a single time point in routine assays. Unplanted microcosmsshowed high SRR of 177 nmol cm^-3 d^-1 inthe uppermost centimeter where average sulfate concentrations were<33 µM. Fine scaled measurements (1 mmresolution) localized highest SRR (<100 nmol cm^-3d^-1) at the oxic/anoxic interface at 2–5 mmdepth. In planted rice field soil, SRR of <310 nmolcm^-3 d^-1 were observed at 0–2cm depth. Sulfate reduction rates were determined at a millimeter-scalewith distance to a two dimensional root compartment. The SRR was highestat 0–1.5 mm distance to the root layer with rates up to500 nmol cm^-3 d^-1, indicating a highstimulation potential of the rice roots. SRR seemed to be mainlydependent on the in situ sulfate porewater concentrations. At thesoil surface of unplanted microcosms sulfate concentration decreasedfrom <150 µM to <10 µM within the first 8 mm of depth. In planted microcosmssulfate concentration varied from 87–99 µMsulfate at the 0–3 mm distance to the root layer to48–62 µM sulfate at a root distance>4 mm from the roots.The depth distribution of inorganic sulfur compounds was determinedfor planted and unplanted rice field soil. Sulfate, acid volatilesulfide (AVS) and chromium reducible sulfide (CRS) were up to 20 foldhigher in planted than in unplanted microcosms. CRS was the majorinsoluble sulfur fraction with concentrations >1.7µmol cm^-3. Organic sulfur accounted for25–46% of the total sulfurpresent (269 µg/g dw) in an unplanted microcosm.The biogeochemical role of sulfate reduction forshort-term accumulation of inorganic sulfur compounds(FeS, FeS_{_2} and S°) in rice soil wasdetermined in a time course experiment with incubationperiods of 5, 10, 20, 30 and 60 min. The relativedistribution of CRS and AVS formation showedlittle depth dependence, whereas the formation of³⁵S° seemed to be the highest in themore oxidized upper soil layers and near the root surface.AV³⁵S was the first major product of sulfatereduction after 20–30 min, whereas CR³⁵Swas formed, as AV³⁵S and ³⁵S°decreased, at longer incubation periods of >30 min.     

Influence of environmental factors on reductive bioprecipitation of uranium by sulfate reducing bacteria

Microbial reduction of soluble uranyl [U (VI)] to insoluble uraninite by sulfate reducing bacteria (SRB) is a promising remediation strategy for uranium-contaminated groundwater. Effects of environmental factors, including pH and coexisting ions, on U (VI) bioreduction processes (UBP) remain unknown. Anaerobic batch experiments were performed to evaluate impact on UBP. Kinetic investigations with varied pH demonstrated that U (VI) was reduced mostly within 48 h. The bioprecipitation yields depended strongly on pH, increasing from 12.9% to 99.4% at pH 2.0 and 6.0, respectively. Sulfate concentration 4000 mg l⁻¹ did not affect UBP; however, sulfate concentration 5000 mg l⁻¹ significantly slowed UBP. Biogenic H₂S produced during sulfate reduction was not directly involved in UBP. At 20 mg l⁻¹ Zn or 10 mg l⁻¹ Cu, no UBP inhibition was observed and uraninite was detected in metal sulfide precipitate. However, 25 mg l⁻¹ Zn or 15 mg l⁻¹ Cu stopped UBP completely. Cu toxicity mechanism probably differed from Zn. The ability to reduce U (VI) was lost permanently with exposure to 15 mg l⁻¹ Cu, but not for Zn 25 mg l⁻¹. No uraninite could be detected before nitrate removal, suggesting nitrate strongly inhibited UBP, which may possibly be related to denitrification intermediates controlling the solution redox potential.     

Recent advances in microbial capture of hydrogen sulfide from sour gas via sulfur‐oxidizing bacteria

Biological desulfurization offers several remarkably environmental advantages of operation at ambient temperature and atmospheric pressure, no demand of toxic chemicals as well as the formation of biologically re‐usable sulfur (S⁰), which has attracted increasing attention compared to conventionally physicochemical approaches in removing hydrogen sulfide from sour gas. However, the low biomass of SOB, the acidification of process solution, the recovery of SOB, and the selectivity of bio‐S⁰ limit its industrial application. Therefore, more efforts should be made in the improvement of the BDS process for its industrial application via different research perspectives. This review summarized the recent research advances in the microbial capture of hydrogen sulfide from sour gas based on strain modification, absorption enhancement, and bioreactor modification. Several efficient solutions to limitations for the BDS process were proposed, which paved the way for the future development of BDS industrialization.     

Protective mechanisms of hydrogen sulfide in myocardial ischemia

Hydrogen sulfide (H₂S), which has been identified as the third gaseous signaling molecule after nitric oxide (NO) and carbon monoxide (CO), plays an important role in maintaining homeostasis in the cardiovascular system. Endogenous H₂S is produced mainly by three endogenous enzymes: cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfur transferase. Numerous studies have shown that H₂S has a significant protective role in myocardial ischemia. The mechanisms by which H₂S affords cardioprotection include the antifibrotic and antiapoptotic effects, regulation of ion channels, protection of mitochondria, reduction of oxidative stress and inflammatory response, regulation of microRNA expression, and promotion of angiogenesis. Amplification of NO- and CO-mediated signaling through crosstalk between H₂S, NO, and CO may also contribute to the cardioprotective effect. Exogenous H₂S donors are expected to become effective drugs for the treatment of cardiovascular diseases. This review article focuses on the protective mechanisms and potential therapeutic applications of H₂S in myocardial ischemia.     

硫酸盐还原菌Desulfotomaculum reducens ZTS1厌氧降解昭通褐煤

[目的] 以云南昭通褐煤为研究对象,从矿井水富集产物中分离得到SRB菌株Desulfotomaculum reducens ZTS1厌氧降解褐煤,分析研究SRB菌株处理褐煤前后的物化性质变化。[方法] 采用工业和元素分析、XRD、FT-IR、SEM和低温液氮吸附法比较研究SRB厌氧降解褐煤前后矿物组成、有机官能团、表面形貌和孔隙结构变化。[结果] D.reducens ZTS1厌氧降解褐煤后灰分和挥发分略有降低,碳、氮和硫元素的含量降低,氧的含量增加,煤中硫代硫酸钠消失,FT-IR结果表明褐煤长链烃上的甲基和亚甲基团增多,游离羟基减少。煤表面粗糙度增加,小孔径的孔隙增多,孔径比表面积增大。[结论] D.reducens ZTS1可以厌氧降解昭通褐煤,厌氧降解后煤的物化性质发生变化。     

Factors affecting microbial sulfate reduction by Desulfovibrio desulfuricans in continuous culture: limiting nutrients and sulfide concentration

The effects of sulfate and nitrogen concentrations of the rate and stoichiometry of microbial sulfate reduction were investigated for Desulfovibrio desulfuricans grown on lactate and sulfate in a chemostat at pH 7.0. Maximum specific growth rates (mu(max)), half-saturation coefficients (K(sul)), and cell yield (Y(c/Lac)) of 0.344 +/- 0.007 and 0.352 +/- 0.003 h (-1), 1.8 +/- 0.3 and 1.0 +/- 0.2 mg/L, and 0.020 +/- 0.003 and 0.017 +/- 0.003 g cell/g lactate, respectively, were obtained under sulfate-limiting conditions at 35 degrees C and 43 degrees C. Maintenance energy requirements for D. desulfuricans were significant under sulfate-limiting conditions. The extent of extracellular polymeric substance (EPS) produced was related to the carbon: nitrogen ratio in the medium. EPS production rate increased with decreased nitrogen loading rate. Nitrogen starvation also resulted in decreased cell size of D. desulfuricans. The limiting C : N ratio (w/w) for D. desulfuricans was in the range of 45 : 1 to 120 : 1. Effects of sulfide on microbial sulfate reduction, cell size, and biomass production were also ivestigated at pH 7.0. Fifty percent inhibition of lactate utilization occurred at a total sulfide concentration of approximately 500 mg/L. The cell size of D. desulfuricans decreased with increasing total sulfide concentration. Sulfide inhibition of D. desulfuricans was observed to be a reversible process. (c) 1992 John Wiley & Sons, Inc.     

Carbon assimilation pathways in sulfate reducing bacteria. Formate,carbon dioxide,carbon monoxide,and acetate assimilation by Desulfovibrio baarsii

Desulfovibrio baarsii is a sulfate reducing bacterium, which can grown on formate plus sulfate as sole energy source and formate and CO₂ as sole carbon sources. It is shown by ¹⁴C labelling studies that more than 60% of the cell carbon is derived from CO₂ and the rest from formate. The cells thus grow autotrophically. Labelling studies with [¹⁴C]acetate, ¹⁴CO and [¹⁴C]formate indicate that CO₂ fixation does not proceed via the Calvin cycle. The labelling patterns of alanine, aspartate, glutamate, and glucosamine indicate that acetate (or activated acetic acid) is an early intermediate in formate and CO₂ assimilation; the methyl group of acetate is derived from formate, and the carboxyl group from CO₂ via CO; pyruvate is formed from acetyl-CoA by reductive carboxylation. The capacity to synthesize an acetate unit from two C₁-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO₂.     

初始底物浓度对序批式培养光合细菌产氢动力学影响

实验研究了初始底物浓度对序批式培养光合细菌生长、降解及产氢过程的影响,根据最大比生长速率实验数据拟合得到其关于初始底物浓度影响的关联式,并在建立的修正Monod模型基础上建立了光合细菌比生长速率、基质比消耗速率和比产氢速率关于底物初始浓度影响的数学模型,模型预测值与实验结果在光合细菌生长期和稳定期内得到较好吻合,反映了光合细菌生长、降解和产氢过程中受底物初始浓度限制性和抑制性影响的基本规律。分析发现光合细菌生长、降解基质和产氢过程中最适底物浓度为50 mmol/L,初始底物浓度低于或高于该浓度时,光合细菌生长、降解及产氢过程都受到限制性或抑制性影响,且抑制性影响较限制性影响效果更明显;底物比消耗速率受初始底物浓度影响较小。     

Synthesis and biological evaluation of novel hydrogen sulfide releasing glycyrrhetic acid derivatives

A series of hybrids, which are composed of glycyrrhetic acid (GA) and slowly hydrogen sulfide-releasing donor ADT-OH, were designed and synthesized to develop anticancer and anti-inflammatory agents. Most of the compounds, whose inhibitory rates were comparable to or higher than those of GA and aspirin, respectively, significantly inhibited xylene-induced ear edema in mice. Especially, compound V₄ exhibited the most potent inhibitory rate of 60.7%. Furthermore, preliminary structure–activity relationship studies demonstrated that 3-substituted GA derivatives had stronger anti-inflammatory activities than the corresponding 3-unsubstituted GA derivatives. In addition, anti-proliferative activities of compounds V_1?9 were evaluated in three different human cancer cell lines. Compound V₄ showed the most high potency against all three tumor cell lines with IC₅₀ values ranging from 10.01?μM in Hep G2 cells to 17.8?μM in MDA-MB-231 cells, which were superior to positive GA.