Assimilatory reduction of sulfate and sulfite by methanogenic bacteria.

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and delta H grew well with S0, SO3(2-), or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO4(2-) as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO4(2-) or SO2(2-) and Methanobacterium thermoautotrophicum Marburg on SO3(2-) but not to growth of strain delta H on SO3(2-). Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO4(2-), SO3(2-), thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO3(2-), or thiosulfate as the sole sulfur source.     

Assimilatory reduction of sulfate and sulfite by methanogenic bacteria

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and delta H grew well with S0, SO3(2-), or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO4(2-) as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO4(2-) or SO2(2-) and Methanobacterium thermoautotrophicum Marburg on SO3(2-) but not to growth of strain delta H on SO3(2-). Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO4(2-), SO3(2-), thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO3(2-), or thiosulfate as the sole sulfur source.     

Isolation and characterization of methanogenic bacteria from rice paddies

Abstract Enrichment cultures for H₂-CO₂, methanol- or acetate-utilizing methanogens were prepared from two rice field soil samples. All the cultures except one acetate enrichment showed significant methane production. Pure cultures of Methanobacterium - and Methanosarcina -like organisms were isolated from H₂-CO₂ and methanol enrichment cultures, respectively, and were characterized for various nutritional and growth conditions. The organisms had an optimal pH range of 6.4–6.6 and a temperature optimum of 37°C. The Methanobacterium isolates were able to utilize H₂-CO₂ but no other substrates as sole energy source, while the Methanosarcina isolates were able to utilize methanol, methylamines or H₂-CO₂ as sole energy sources. Both Methanobacterium isolates and one isolate of Methanosarcina were able to use dinitrogen as the sole source of nitrogen for growth. The isolates used several sulfur compounds as sole sources of sulfur.     

Sulfur from benzothiophene and alkylbenzothiophenes supports growth of <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. strain JVH1

Rhodococcus sp. strain JVH1 was previously reported to use a number of compounds with aliphatic sulfide bridges as sulfur sources for growth. We have shown that although JVH1 does not use the three-ring thiophenic sulfur compound dibenzothiophene, this strain can use the two-ring compound benzothiophene as its sole sulfur source, resulting in growth of the culture and loss of benzothiophene. Addition of inorganic sulfate to the medium reduced the conversion of benzothiophene, indicating that benzothiophene metabolism is repressed by sulfate and that benzothiophene is therefore used specifically as a sulfur source. JVH1 also used all six isomers of methylbenzothiophene and two dimethylbenzothiophene isomers as sulfur sources for growth. Metabolites identified from benzothiophene and some methylbenzothiophenes were consistent with published pathways for benzothiophene biodesulfurization. Products retaining the sulfur atom were sulfones and sultines, the sultines being formed from phenolic sulfinates under acidic extraction conditions. With 2-methylbenzothiophene, the final desulfurized product was 2-methylbenzofuran, formed by dehydration of 3-(o-hydroxyphenyl) propanone under acidic extraction conditions and indicating an oxygenative desulfination reaction. With 3-methylbenzothiophene, the final desulfurized product was 2-isopropenylphenol, indicating a hydrolytic desulfination reaction. JVH1 is the first microorganism reported to use all six isomers of methylbenzothiophene, as well as some dimethylbenzothiophene isomers, as sole sulfur sources. JVH1 therefore possesses broader sulfur extraction abilities than previously reported, including not only sulfidic compounds but also some thiophenic species.     

Isolation and characterization of thermophilic methanogenic bacteria from mushroom compost

Abstract During the first stage of the preparation of mushroom compost oxygen is believed to be readily available. However we measured methane in the evoking air above the compost piles and were able to isolate thermophilic methanogenic bacteria from this compost. The isolates grow only on H₂ and CO₂ as energy and carbon source and do not require complex factors for growth. On the basis of nutritional and morphological characteristics these methanogens were identified as strains of Methanobacterium thermoautotrophicum .     

Nutritional studies with Pseudomonas aeruginosa grown on inorganic sulfur sources.

Pseudomonas aeruginosa was grown on a succinate-basal salts medium supplemented with various inorganic sulfur compounds as its sole source of sulfur. The organism was able to grow on the sodium salts of sulfide, thiosulfate, tetrathionate, dithionite, metabisulfite, sulfite, or sulfate, but not on those of dithionate. Analyses of the culture media after 24 h of growth indicated accumulation of sulfate from each inorganic sulfur source except sulfate. Manometric studies with resting cells obtained by growth on each of these sulfur sources yielded net oxygen uptake for all substrates except sulfite and dithionate. Similar results were obtained with extracts from these cells by spectrophotometric techniques. Thiosulfate oxidase activity appeared to be induced by growth on sulfide, thiosulfate, or tetrathionate, with little or no activity observed when cells were grown on inorganic sulfur sources of higher oxidative states. Metabisulfite oxidase appeared to be associated with growth on all inorganic sulfur compounds. Rhodanese activity appeared to be constitutively present, and its activity, observed only in soluble fraction, seemed independent of the growth medium employed. Thiosulfate and tetrathionate oxidase activities were studied in greater detail than some of the other sulfur oxidases, and both were found to be distributed between particulate and soluble fractions.     

Nutrition and factors limiting the growth of a methanogenic bacterium (Methanobacterium thermoautotrophicum)

The purification of Methanobacterium thermoautotrophicum from a culture contaminated with a heterotrophic organism is described. A defined inorganic medium under H₂/CO₂ (80:20 v/v) has been developed to support growth of M. thermoautotrophicum up to a concentration of at least 1.7 g dry weight/l. In a conventional medium iron and nitrogen sources were found to be growth-limiting factors. Throughout most of the culture period the rate of transfer of hydrogen or carbon dioxide from gas to liquid was the factor which controlled the growth rate.The growth yields of bacteria were in the range 0.6–1.6 g dry weight/mole CH₄.Abbreviation TGP thioglycollate peptone medium     

九株嗜热产甲烷菌的特性

从处理生活废水的厌氧污泥床的4个样品中,分离、纯化了9株嗜热的、利用H_2/CO_2和甲酸盐产甲烷的细菌。它们在细胞形态和生理特性上基本一致。细胞为直或略弯的杆状,两端钝圆,0.3～0.4×1～3μm;单个、成对,或多个相联,可达10μm以上。革兰氏阳性,不运动。细胞和菌落在荧光显微镜下呈现产甲烷菌所特有的绿色荧光。化能自养。生长温度30～75℃以下,最适为55～65℃。生长pH5.8～9.0,最适为6.9～7.6。菌株602B_3DNA中G+C含量为44.6mol％。将该菌株鉴定为嗜热甲酸甲烷杆菌的不同菌株:Methanobacterium thermoformicicum 602B_3     

Carbon nanotubes accelerate methane production in pure cultures of methanogens and in a syntrophic coculture

Carbon materials have been reported to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens improving methane production in anaerobic processes. In this work, the effect of increasing concentrations of carbon nanotubes (CNT) on the activity of pure cultures of methanogens and on typical fatty acid‐degrading syntrophic methanogenic coculture was evaluated. CNT affected methane production by methanogenic cultures, although acceleration was higher for hydrogenotrophic methanogens than for acetoclastic methanogens or syntrophic coculture. Interestingly, the initial methane production rate (IMPR) by Methanobacterium formicicum cultures increased 17 times with 5 g·L^?1 CNT. Butyrate conversion to methane by Syntrophomonas wolfei and Methanospirillum hungatei was enhanced (～1.5 times) in the presence of CNT (5 g·L^?1), but indications of DIET were not obtained. Increasing CNT concentrations resulted in more negative redox potentials in the anaerobic microcosms. Remarkably, without a reducing agent but in the presence of CNT, the IMPR was higher than in incubations with reducing agent. No growth was observed without reducing agent and without CNT. This finding is important to re‐frame discussions and re‐interpret data on the role of conductive materials as mediators of DIET in anaerobic communities. It also opens new challenges to improve methane production in engineered methanogenic processes.     

Sulfide-Dependent Methane Production and Growth of a Thermophilic Methanogenic Bacterium

Two strains of a thermophilic methanogenic bacterium, designated MT1 a and b, were isolated from a coastal surface sediment in the northern part of the Swedish West Coast. The two strains were identical in appearance and nutritional requirements and resembled Methanobacterium thermoautotrophicum. MT1 had an extraordinary requirement for sulfide. At sulfide levels below 0.1 mM, growth was poor and the methane production rate decreased. Other sources of sulfur, such as cysteine, sulfate, or thiosulfate, could not replace sulfide. The results indicate that a fast turnover rate of reduced sulfur compounds is involved in the energy metabolism of this organism.