Survival of microorganisms during two-year exposure in outer space near the ISS

Results of an experiment named "Test" on survival and variability of microorganisms in open space near the International Space Station are presented. It was found after two-years exposure, spore-forming bacteria of the species Bacillus subtilis, fungi of the species Aureobasidium pullulans and archaea of the species Methanosarcina mazei S-6T, deposited on cotton wool, are able to survive, and their numbers decreased equally, regardless of whether the microorganisms belong to different taxonomic groups. The main factors for the long-term survival could be the result of their dehydration and partial lyophilization in the vacuum of near-Earth space. For the first time, after being in outer space, cyst-like cells of the archaea strain M. mazei S-6T and a 14-day delay in their growth were detected when cultured on a nutrient medium compared to the ground-based control strain. In 30% of fungi species strains A. pullulans, isolated after a two-year stay in outer space, the resistance to γ-radiation increased compared to the control strain. It was found that the reaction to the action of various concentrations of hydrogen peroxide and 1% chlorine in the surviving strains of the fungus A. pullulans on the ISS is less pronounced than in the control strain.

Microorganisms for the oxidation of nitrated cellulose in its effluents (review)

The processes of microbiological destruction of toxic and large-tonnage waste are the most attractive processes for protecting the environment. The review considers the results of studies of microbial decomposition of nitrate esters, including hardly decomposable nitrocellulose. The published data show that specific microorganisms are able to degrade nitrated cellulose compounds under both anaerobic and aerobic conditions. The most promising microorganisms in terms of the efficiency of the nitrocellulose degradation process are bacteria belonging to Desulfovibrio genera, fungi Fusarium solani and Sclerotium rolfsii, as well as their co-cultivation. Recently, the first information about the enzymes involved in the process of nitrocellulose degradation, possible mechanisms of reactions carried out by these enzymes, and the effect of electron donors and acceptors adding to the process have been obtained. Contamination of industrial wastewater with nitrocellulose leads to treatment necessity by using cost-effective, harmless methods. A combined aerobic-anaerobic system, including both bacteria and fungi, has shown hopeful results.

Biogeochemical Characteristics of Earth's Volcanic Permafrost: An Analog of Extraterrestrial Environments

This article describes a study of frozen volcanic deposits collected from volcanoes Tolbachik and Bezymianny on the Kamchatka Peninsula, Russia, and Deception Island volcano, Antarctica. In addition, we studied suprasnow ash layers deposited after the 2007 eruptions of volcanoes Shiveluch and Bezymianny on Kamchatka. The main objectives were to characterize the presence and survivability of thermophilic microorganisms in perennially frozen volcanic deposits. As opposed to permafrost from the polar regions, viable thermophiles were detected in volcanic permafrost by cultivation, microscopy, and sequencing. In the permafrost of Tolbachik volcano, we observed methane formation by both psychrophilic and thermophilic methanogenic archaea, while at 37°C, methane production was noticeably lower. Thermophilic bacteria isolated from volcanic permafrost from the Deception Island were 99.93% related to Geobacillus stearothermophilus. Our data showed biological sulfur reduction to sulfide at 85°C and even at 130°C, where hyperthermophilic archaea of the genus Thermoproteus were registered. Sequences of hyperthermophilic bacteria of the genus Caldicellulosiruptor were discovered in clone libraries from fresh volcanic ash deposited on snow. Microorganisms found in volcanic terrestrial permafrost may serve as a model for the alien inhabitants of Mars, a cryogenic planet with numerous volcanoes. Thermophiles and hyperthermophiles and their metabolic processes represent a guideline for the future exploration missions on Mars.

Diplocloster agilis gen. nov., sp. nov. and Diplocloster modestus sp. nov., two novel anaerobic fermentative members of Lachnospiraceae isolated from human faeces

Three novel strains of Gram-stain-negative, obligately anaerobic, spore-forming straight or slightly curved rods with pointed ends occurring singly or in pairs were isolated from the faeces of healthy human children. The strains were characterized by mesophilic fermentative metabolism and production of acetate, ethanol and H2 as the end metabolic products. Strains ASD3451 and ASD5720T were motile, fermented lactose and raffinose, and weakly fermented maltose. Strain ASD4241T was non-motile and did not ferment the carbohydrates listed above but fermented starch. Strains ASD3451 and ASD5720T shared average nucleotide identity higher than 98.5 % with each other, while ASD4241T had only 88.5-89 % identity to them. Based on phylogenetic and chemotaxonomic analyses, we propose Diplocloster agilis gen. nov., sp. nov. (ASD5720T=JCM 34353T=VKM B-3497T) and Diplocloster modestus sp. nov. (ASD4241T=JCM 34351T=VKM B-3498T) within the family Lachnospiraceae .

Desulfosporosinus metallidurans sp. nov., an acidophilic, metal-resistant sulfate-reducing bacterium from acid mine drainage

A novel, spore-forming, acidophilic and metal-resistant sulfate-reducing bacterium, strain OL^T, was isolated from a microbial mat in a tailing dam at a gold ore mining site. Cells were slightly curved immotile rods, 0.5 µm in diameter and 2.0-3.0 µm long. Cells were stained Gram-negative, despite the Gram-positive cell structure revealed by electron microscopy of ultrathin layers. OL^T grew at pH 4.0-7.0 with an optimum at 5.5. OL^T utilised H₂, lactate, pyruvate, malate, formate, propionate, ethanol, glycerol, glucose, fructose, sucrose, peptone and tryptone as electron donors for sulfate reduction. Sulfate, sulfite, thiosulfate, nitrate and fumarate were used as electron acceptors in the presence of lactate. Elemental sulfur, iron (III), and arsenate did not serve as electron acceptors. The major cellular fatty acids were C_16:1ω7c (39.0 %) and C_16 : 0 (12.1 %). The draft genome of OL^T was 5.29 Mb in size and contained 4909 protein-coding genes. The 16S rRNA gene sequence placed OL^T within the phylum Firmicutes, class Clostridia, family Peptococcaceae, genus Desulfosporosinus. Desulfosporosinus nitroreducens 59.4B^T was the closest relative with 97.6 % sequence similarity. On the basis of phenotypic and phylogenetic characteristics, strain OL^T represents a novel species within the genus Desulfosporosinus, for which we propose the name Desulfosporosinus metallidurans sp. nov. with the type strain OL^T (=DSM 104464^T=VKM В-3021^T).

Sphaerochaeta halotolerans sp. nov., a novel spherical halotolerant spirochete from a Russian heavy oil reservoir, emended description of the genus Sphaerochaeta, reclassification of Sphaerochaeta coccoides to a new genus Parasphaerochaeta gen. nov. as Parasphaerochaeta coccoides comb. nov. and proposal of Sphaerochaetaceae fam. nov

Anaerobic, fermentative, halotolerant bacteria, strains 4-11^T and 585, were isolated from production water of two low-temperature petroleum reservoirs (Russia) and were characterized by using a polyphasic approach. Cells of the strains were spherical, non-motile and 0.30-2.5 µm in diameter. Strain 4-11^T grew optimally at 35 °C, pH 6.0 and 1.0-2.0% (w/v) NaCl. Both strains grew chemoorganotrophically with mono-, di- and trisaccharides. The major cellular fatty acids of both strains were C_14:0, C_16:0, C_16:1 ω9 and C_18:0 3-OH. Major polar lipids were glycolipids and phospholipids. The 16S rRNA gene sequences of the strains 4-11^T and 585 had 99.9% similarity and were most closely related to the sequence of Sphaerochaeta associata GLS2^T (96.9, and 97.0% similarity, respectively). The G+C content of the genomic DNA of strains 4-11^T and 585 were 46.8 and 46.9%, respectively. The average nucleotide identity and digital DNA-DNA hybridization values between the genomes of strain 4-11^T and S. associata GLS2^T were 73.0 and 16.9%, respectively. Results of phylogenomic metrics analysis of the genomes and 120 core proteins of strains 4-11^T and 585 and their physiological and biochemical characteristics confirmed that the strains represented a novel species of the genus Sphaerochaeta, for which the name Sphaerochaeta halotolerans sp. nov. is proposed, with the type strain 4-11^T (=VKM B-3269^T=KCTC 15833^T). Based on the results of phylogenetic analysis, Sphaerochaeta coccoides was reclassified as member of a new genus Parasphaerochaeta gen. nov., Parasphaerochaeta coccoides comb. nov. The genera Sphaerochaeta and Parasphaerochaeta form a separate clade, for which a novel family, Sphaerochaetaceae fam. nov., is proposed.

Developing a technique to enhance durability of fibrous ion-exchange resin substrate for space greenhouses

One way to cut consumables for space plant growth facilities (PGF) with artificial soil in the form of fibrous ion-exchange resin substrate (FIERS) is on-board regeneration of the used medium. After crop harvest the procedure includes removal of the roots from the fibrous media with preservation of the exchanger properties and capillary structure. One type of FIERS, namely BIONA-V3ۛ, has been used in Russian prototypes of space conveyors. We describe a two-stage treatment of BIONA-V3ۛ including primary microwave heating of the used FIERS until (90 ± 5) °C in alkali-peroxide solution during 3.5 hrs. The second stage of the treatment is decomposition of root vestiges inside pores of BIONA-V3ۛ by using thermophilic and mesophilic anaerobic bacteria Clostridium thermocellum, Clostridium cellulolyticum and Cellulosilyticum lentocellum during 7-10 days at 55 °C. The two-stage procedure allows extraction of 90% dead roots from the FIERS' pores and the preservation of root zone hydro-physical properties. A posterior enrichment of the FIERS by minerals makes BIONA- V3ۛ reusable.

[Anaerobic bacteria involved in the degradation of aromatic sulfonates to methane]

An anaerobic microbial consortium that degrades benzene- and p-toluenesulfonate to form methane and fatty acids has been produced. Pure cultures of three strains of anaerobic spore-forming bacteria Clostridium spp., as well as the sulfate-reducing bacteria Desulfovibrio sp., were isolated and characterized. Phylogenetic analysis of 16S rRNA gene sequences of strains showed that pure cultures of clostridia strains 14, 24, and 21 are close to Clostridium lituseburense DSM 797T, C. sartagoforme DSM 1292T, and C. pascui DSM 10365T, and the sulfate-reducing strain SR1 is genotypically closer to Desulfovibrio aminophilus ALA-3T. Preliminary characterization of isolated bacteria makes it possible to assume that these are new species of the genera Clostridium and Desulfovibrio, the distinctive feature of which is the ability to incorporate aromatic sulfonates in their metabolisms.

[Prolonged cultivation of an anaerobic bacterial community producing hydrogen]

This paper studies various methods of long-term maintenance of the process of hydrogen evolution during the growth of an aerobic bacterial community on a starch-containing environment. When cultured in separable trip fermentation mode for 72 days, from 0.10 to 0.23 H2/l of medium/day was formed. The regime of regular reseeding lasted more than 100 days, forming an average of 0.81 1 H2/l of medium/day. The advantages and disadvantages of different methods of microbial hydrogen production during a dark starch fermentation process are presented. From the obtained H2 forming microbial communities, we isolated an anaerobic spore-forming bacterium (strain BF). Phylogenetic analysis of the 16S RNA gene sequence of the new strain showed that according to its genotype it belongs to the Clostridium butyricum species.

Desulfovibrio arcticus sp. nov., a psychrotolerant sulfate-reducing bacterium from a cryopeg

A psychrotolerant sulfate-reducing bacterium, designated B15T, was isolated from supercooled water brine from within permafrost of the Varandey Peninsula, on the southern coast of the Barents Sea. Cells were Gram-negative, motile vibrions (3.0–4.0×0.4–0.5 µm) with a single polar flagellum. The isolate was positive for desulfoviridin as a bisulfite reductase. Strain B15T grew at −2 to 28 °C (optimum 24 °C) and with 0–2.0 % NaCl (optimum 0.2 %). The isolate used H2 plus acetate, formate, ethanol, lactate, pyruvate and choline as electron donors and used sulfate, sulfite, thiosulfate, elemental sulfur, DMSO and Fe3+ as electron acceptors. Pyruvate and lactate were not fermented in the absence of sulfate. The G+C content of genomic DNA was 55.2 mol%. Analysis of the 16S rRNA gene sequence showed that the isolate belonged to the genus Desulfovibrio. Its closest relatives were Desulfovibrio idahonensis CY1T (98.8 % 16S rRNA gene sequence similarity) and Desulfovibrio mexicanus Lup1T (96.5 %). On the basis of genotypic, phenotypic and phylogenetic characteristics, the isolate represents a novel species, for which the name Desulfovibrio arcticus sp. nov. is proposed; the type strain is B15T ( = VKM B-2367T = DSM 21064T).

[Methods of extending the resource of fiber ionite artificial soils in space greenhouses]

The vegetable cultivation technology developed in view of long-term autonomous missions is based on root nutrition provided by fiber artificial soils (AS) containing ion-exchange resins. Useful life of ASs is limited by two factors which are nutrients depletion in ion-exchanger and clogging of the AS threshold space by roots remnants. Purpose of the investigation is to try out hydrolysis and ensuing microbial decomposition of roots remnants as a way to extend the resource of used fiber ionite AS. This principle of doing away with the roots remnants recovers almost completely the maximal water-absorbing capacity of AS BIONA-V3 so that it can be used again for crops cultivation.

Methanobacterium veterum sp. nov., from ancient Siberian permafrost

A methanogenic archaeon, strain MK4(T), was isolated from ancient permafrost after long-term selective anaerobic cultivation. The cells were rods, 2.0-8.0 microm long and 0.40-0.45 microm wide, and stained Gram-negative. Optimal growth was observed at 28 degrees C and pH 7.0-7.2 and in 0.05 M NaCl. The isolate used H(2) plus CO(2), methylamine plus H(2) and methanol plus H(2) as sources for growth and methanogenesis. Phylogenetic analysis of the 16S rRNA gene sequence of the strain showed close affinity with Methanobacterium bryantii (similarity >99 % to the type strain). On the basis of the level of DNA-DNA hybridization (62 %) between strain MK4(T) and Methanobacterium bryantii VKM B-1629(T) and phenotypic and phylogenetic differences, strain MK4(T) was assigned to a novel species of the genus Methanobacterium, Methanobacterium veterum sp. nov., with the type strain MK4(T) (=DSM 19849(T) =VKM B-2440(T)).

Clostridium tagluense sp. nov., a psychrotolerant, anaerobic, spore-forming bacterium from permafrost

A strictly anaerobic, Gram-positive, psychrotolerant, endospore-forming bacterium (strain A121(T)) was isolated from a permafrost sample collected in the Canadian High Arctic. Phylogenetic analysis of the 16S rRNA gene sequence of strain A121(T) showed its affiliation with the group of psychrophilic and psychrotolerant members of cluster I of the genus Clostridium, Clostridium bowmanii DSM 14206(T) being the closest relative (sequence similarity 98.5 %). Levels of DNA-DNA relatedness between strain A121(T) and the type strains of phylogenetically related species ranged from 33 to 52 %. Strain A121(T) grew in PY broth at temperatures between 4 and 28 degrees C (optimum 15-20 degrees C), at pH 6.0-8.0 (optimum pH 6.5-7.2) and in NaCl concentrations of 0-10.0 % (optimum 0-2.0 %). The strain utilized a narrow range of carbohydrates as sources of carbon and energy, including glucose, fructose, trehalose, maltose and starch; it also hydrolysed gelatin. Predominant fatty acids were C(16 : 1) cis9, C(16 : 1) cis9 DMA, C(16 : 0) and C(14 : 0). The DNA G+C content was 31.5 mol%. On the basis of its overall genotypic and phenotypic characteristics, strain A121(T) is classified within a novel species of the genus Clostridium, Clostridium tagluense sp. nov. The type strain is A121(T) (=VKM B-2369(T) =DSM 17763(T)).

[Novel halotolerant bacterium from cryopeg in permafrost: description of Psychrobacter muriicola sp. nov]

A novel halotolerant psychrotrophic gram-negative bacterium, strain 2pS, was isolated from lenses of water brine in Arctic permafrost (cryopeg). The optimal growth of the new strain was observed at 16-18 degrees C; the maximal and minimal growth temperatures were 37 degrees C and -2 degrees C, respectively. The pH growth range was 5.8 to 8.5 (optimum 6.5-7.5) and the range of medium salinity was 0 to 100 g/l (optimum 3-8 g/l NaCl). The strain 2pS did not produce acid from carbohydrates and utilized acetate, yeast extract, pyruvate, glutarate, fumarate, caproate, heptanoate, butyrate, malate, DL-lactate, citrate, L-proline, L-tyrosine, butanol, and dulcitol as the sole carbon and energy sources. The major fatty acids of the cell wall at optimal growth temperature were C18:1(omega 7) and C18:1(omega 9). The G + C DNA content was 46.0 mol.%. Phylogenetic analysis of the 16S rRNA gene sequences showed that the studied strain was the closest (97% similarity) to Psychrobacter nivimaris DSM 16093T, a halotolerant psychrotrophic bacterium isolated from the Arctic sea's ice. Genotypic and phenotypic differences of the new bacterium from closely related species lead to the conclusion that strain 2pS belongs to a novel species of the genus Psychrobacter: Psychrobacter muriicola sp. nov.

[Effect of vitamin concentration on the synthesis of lactate, ethanol, pyruvate, and ethyl acetate in cells of the yeast Dipodascus magnusii]

In the yeast Dipodascus magnusii, which is auxotrophic for thiamine and biotin, during cultivation on glucose with excessive thiamine concentration, pyruvate metabolism was shown to result in the synthesis of fermentation products, namely, ethanol and, to a lesser extent, lactate. Substantial synthesis of ethyl acetate was also observed under these conditions. Introduction of nicotinic acid (NA) into the medium resulted in time separation of ethanol and lactate production. It was shown that cultivation of the yeast under biotin deficiency resulted in nearly complete suppression of aerobic production of ethanol and cessation of ethyl acetate synthesis, whereas lactate synthesis was activated as early as in the first hours of cultivation. Upon introduction of NA under these conditions, lactate concentration sharply increased. These results show that the combination of thiamine and biotin with other vitamins can stimulate utilization of the pyruvate pool in yeasts towards formation of considerable amounts of lactate, which is typical only of cells of higher eukaryotes and bacteria.

[Interrelation between the pathways of isoprenoid biosynthesis and carbon source catabolism in anaerobic and facultatively anaerobic bacteria]

Data on the interrelation between the pathways of the carbon source catabolism and isoprenoid biosynthesis in anaerobic and facultatively anaerobic bacteria were obtained. Two pathways of isoprenoid biosynthesis (nonmevalonate and mevalonate) were revealed in the representatives of the genus Clostridium. The non-mevalonate pathway of isoprenoid biosynthesis and the glycolytic pathway of substrate oxidation are typical of glucose-grown bacteria, whereas the pentose phosphate cycle operates in xylose-grown bacteria. The mevalonate pathway of isoprenoid biosynthesis was revealed in strain Clostridium thermosaccharolyticum DSM 571 grown in the presence of mevinolin, as well as in a number of lactic acid bacteria. Mevinolin is known to react with the lactate dehydrogenase complex, preventing reduction of pyruvate. The nonmevalonate pathway of isoprenoid biosynthesis was revealed in Bifidobacterium bifidum. The role of different metabolic pathways in isoprenoid biosynthesis is discussed.

[Microbiological analysis of cryopegs from the Varandei Peninsula, Barents Sea]

The paper deals with the microbiological characterization of water-saturated horizons in permafrost soils (cryopegs) found on the Varandei Peninsula (Barents Sea coast), 4-20 m deep. The total quantity of bacteria in the water of cryopegs was 3.5 x 10(8) cells/ml. The population of cultivated aerobic heterotrophic bacteria was 3-4 x 10(7) cells/ml and the number of anaerobic heterotrophic bacteria varied from 10(2) to 10(5) cells/ml depending on cultivation temperature and salinity. Sulfate-reducing bacteria and methanogenic archaea were found as hundreds and tens of cells per ml of water, respectively. A pure culture of a sulfate-reducing strain B15 was isolated from borehole 21 and characterized. Phylogenetic analysis has shown that the new bacterium is a member of the genus Desulfovibrio with Desulfovibrio mexicanus as its closest relative (96.5% similarity). However, the significant phenotypic differences suggest that strain B15 is a new species of sulfate-reducing bacteria.

Microbial populations in Antarctic permafrost: biodiversity, state, age, and implication for astrobiology

Antarctic permafrost soils have not received as much geocryological and biological study as has been devoted to the ice sheet, though the permafrost is more stable and older and inhabited by more microbes. This makes these soils potentially more informative and a more significant microbial repository than ice sheets. Due to the stability of the subsurface physicochemical regime, Antarctic permafrost is not an extreme environment but a balanced natural one. Up to 10(4) viable cells/g, whose age presumably corresponds to the longevity of the permanently frozen state of the sediments, have been isolated from Antarctic permafrost. Along with the microbes, metabolic by-products are preserved. This presumed natural cryopreservation makes it possible to observe what may be the oldest microbial communities on Earth. Here, we describe the Antarctic permafrost habitat and biodiversity and provide a model for martian ecosystems.

Novel psychrophilic anaerobic spore-forming bacterium from the overcooled water brine in permafrost: description Clostridium algoriphilum sp. nov

A gram-positive, motile, strict anaerobic spore-forming bacterium was isolated from the over-cooled brine in the permafrost. The optimal temperature for isolate growth was 5-6 degrees C at pH 6.8-7.2. The bacterium was growing on the medium rich in saccharides and disaccharides. Out of polysaccharides tested, only xylan sustained the growth. Fermentation of the hexoses led to the formation of acetate, butyrate, lactate, H2,CO2 and some formate and ethanol. Cell wall peptidoglycan contained meso-diaminopimelic acid. The major fatty acids of the cell wall were C(14:0) and C(16:1c9). The content of G-C pairs in DNA was 31.4 mol%. As phylogenetic analysis has shown, it is closely linked to the members of cluster 1 of Clostridium. It differs from the other species of the genus by the substrates necessary for the growth, products forming as a result of the fermentation and content of the fatty acids in the cell wall. Thus, it was suggested to describe this strain as a new species named Clostridium algoriphilum. Type strain 14D1 was deposited into the Russian Collection of the Microorganisms VKM B-2271T and German Collection of the Microorganisms DSM 16153T .

[Prevalence of nonmevalonate and mevalonate pathways for isoprenoid biosynthesis among bacteria of different systematic groups]

The effect of fosmidomycin and mevinoline, inhibitors of the nonmevalonate and the mevalonate pathway of isoprenoid biosynthesis, respectively, on the growth of 34 anaerobic and 10 aerobic prokaryotic strains was studied. Fosmidomycin at the concentrations used was shown to inhibit the growth of 9 (of 10) representatives of the family Microbacteriaceae, 4 (of 5) strains of Thermoanaerobacter, and 11 (of 12) strains of Clostridium, whereas mevinoline inhibited the growth of lactobacilli (Carnobacterium), methanogenic and sulfate-reducing bacteria insensitive to fosmidomycin. During the late growth phase, four strains of actinobacteria (of nine) accumulate the compound, which, upon oxidation, generates a long-lived free radical; three strains synthesize 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC). It was concluded that the difference in the sensitivity of the organisms to fosmidomycin and mevinoline might serve as a test to differentiate several representatives of the family Microbacteriaceae. The use of mevinoline for inhibiting methanogens in ecological investigations seems to be promising.

[Analysis of the anaerobic microbial community capable of degrading p-toluene sulphonate]

Three strains of Clostridium sp., 14 (VKM B-2201), 42 (VKM B-2202), and 21 (VKM B-2279), two methanogens, Methanobacterium formicicum MH (VKM B-2198) and Methanosarcina mazei MM (VKM B-2199), and one sulfate-reducing bacterium, Desulfovibrio sp. SR1 (VKM B-2200), were isolated in pure cultures from an anaerobic microbial community capable of degrading p-toluene sulfonate. Strain 14 was able to degrade p-toluene sulfonate in the presence of yeast extract and bactotryptone and, like strain 42, to utilize p-toluene sulfonate as the sole sulfur source with the production of toluene. p-Toluene sulfonate stimulated the growth of Ms. mazei MM on acetate. The sulfate-reducing strain Desulfovibrio sp. SR1 utilized p-toluene sulfonate as an electron acceptor. The putative scheme of p-toluene sulfonate degradation by the anaerobic microbial community is discussed.

[Methanogenic sarcina from an anaerobic microbial community degrading p-toluene sulfonate]

The methanogenic strain MM isolated from an anaerobic microbial community degrading p-toluene sulfonate showed optimal values of temperature and pH for growth equal to 37 degrees C and 6.3-6.9, respectively. The doubling times of the isolate grown on methanol, acetate, and methylamines under the optimal conditions were 8.8, 19.1, and 10.3-28.1 h, respectively. The growth of strain MM was observed only when the cultivation medium contained casamino acids or p-toluene sulfonate. The G + C content of the DNA of the isolate was 40.3 mol%. This, together with DNA-DNA hybridization data, allowed the new isolate to be identified as a strain of the species Methanosarcina mazei. The new isolate differed from the known representatives of this species in that it was resistant to alkylbenzene sulfonates and able to demethylate p-toluene sulfonate when grown on acetate.

[Methane production by the sulfate-reducing bacterium Desulfosarcina variabilis]

The sulfate-reducing bacterium Desulfosarcina variabilis VKM B-1694 was found to produce up to 1.62 mumol methane per mg protein when grown on different substrates. The role of methanogenesis and the physicochemical factors determining this process in sulfate-reducing bacteria are discussed.

Toxic effect of surfactants and probable products of their biodegradation on methanogenesis in an anaerobic microbial community

Surfactants used in household and various industries, are rather toxic; therefore, the accumulation of these compounds in the environment through wastewaters has challenged the problem of their biodegradation. In this research, an attempt was made to assess the toxic effect of various surfactants and the likely products of their biodegradation on the acetoclastic methanogens of an anaerobic microbial community. Among the substances investigated, cationic surfactants were found to be most toxic to methanogens: 154 mg/l alkamon DS and 345 mg/l catamin AB induced a 50% inhibition of methanogenesis. Toxicity studies of some aromatic and cyclic compounds, as the probable products of biodegradation of alkylbenzene sulfonate surfactants, showed that methanogenesis in the microbial community under study are rather tolerant to high concentrations of these compounds.