New species of psychrophilic acetogens: Acetobacterium bakii sp. nov., A. paludosum sp. nov., A. fimetarium sp. nov.

Three strains of new acetogenic bacteria were isolated from several low temperature environments. Cells were gram-positive, oval-shaped flagellated rods. The organisms fermented H₂/CO₂, CO, formate, lactate, and several sugars to acetate. Strains Z-4391 and Z-4092 grew in the temperature range from 1 to 30°C with an optimum at 20°C; strain Z-4290 grew in the range from 1 to 35°C with an optimum at 30°C. The DNA G+C content of strains Z-4391, Z-4092, and Z-4290 was 42.1, 41.7, and 45.8 mol% respectively.     

Diversity of H2/CO2-Utilizing Acetogenic Bacteria from Fecesof Non-Methane-Producing Humans

The purpose of this work was to study H₂/CO₂-utilizing acetogenic population in the colons of non-methane-producing individuals harboring low numbers of methanogenic archaea. Among the 50 H₂-consuming acetogenic strains isolated from four fecal samples and an in vitro semi-continuous culture enrichment, with H₂/CO₂ as sole energy source, 20 were chosen for further studies. All isolates were Gram-positive strict anaerobes. Different morphological types were identified, providing evidence of generic diversity. All acetogenic strains characterized used H₂/CO₂ to form acetate as the sole metabolite, following the stoichiometric equation of reductive acetogenesis. These bacteria were also able to use a variety of organic compounds for growth. The major end product of glucose fermentation was acetate, except for strains of cocci that mainly produced lactate. Yeast extract was not necessary, but was stimulatory for growth and acetogenesis from H₂/CO₂. Received: 28 December 1995 / Accepted: 30 January 1996     

Sulfate reduction with methanol by a thermophilic consortium obtained from a methanogenic reactor

 An enrichment culture obtained from anaerobic granular sludge of a bench-scale anaerobic reactor degraded methanol at 65°C via sulfate reduction and acetogenesis. Sulfate reduction was the dominant process (S^2-/acetate=2.5). No methane formation was observed. Approximately 30% of the methanol was converted by acetogenic bacteria to acetate, while the remainder was degraded by these bacteria to H₂ and CO₂ in syntrophy with hydrogen-consuming sulfate-reducing bacteria. Pure cultures of sulfate-reducing and acetogenic bacteria were isolated and characterized. Received: 4 December 1995 / Received revision: 15 April 1996 / Accepted: 22 April 1996     

Methanocorpusculaceae fam. nov., represented by Methanocorpusculum parvum,Methanocorpusculum sinense spec. nov. and Methanocorpusculum bavaricum spec. nov.

Two new methanogenic bacteria, Methanocorpusculum sinense spec. nov. strain DSM 4274 from a pilot plant for treatment of distillery wastewater in Chengdu (Province Sichuan, China), and Methanocorpusculum bavaricum spec. nov. strain DSM 4179, from a wastewater pond of the sugar factory in Regensburg (Bavaria, FRG) are described. Methanocorpusculum strains are weakly motile and form irregularly coccoid cells, about 1 μm in diameter. The cell envelope consists of a cytoplasmic membrane and a S-layer, composed of hexagonally arranged glycoprotein subunits with molecular weights of 90000 (Methanocorpusculum parvum), 92000 (M. sinense), and 94000 (M. bavaricum). The center-to-center spacings are 14.3 nm, 15.8 nm and 16.0 nm, respectively. Optimal growth of strains is obtained in the mesophilic temperature range and at a pH around 7. Methane is produced from H₂/CO₂, formate, 2-propanol/CO₂ and 2-butanol/CO₂ by M. parvum and M. bavaricum, whereas M. sinense can only utilize H₂/CO₂ and formate. Growth of M. sinense and M. bavaricum is dependent on the presence of clarified rumen fluid. The G+C content of the DNA of the three strains is ranging from 47.7–53.6 mol% as determined by different methods. A similar, but distinct polar lipid pattern indicates a close relationship between the three Methanocorpusculum species. The polyamine patterns of M. parvum, M. sinense and M. bavaricum are similar, but distinct from those of other methanogens and are characterized by a high concentration of the otherwise rare 1,3-diaminopropane. Quantitative comparison of the antigenic fingerprint of members of Methanocorpusculum revealed no antigenic relationship with any one of the reference methanogens tested. On the basis of the distant phylogenetic position of M. parvum and the data presented in this paper a new family, the Methanocorpusculaceae fam. nov., is defined.     

Clostridium mayombei sp. nov., an H2/CO2 acetogenic bacterium from the gut of the African soil-feeding termite,Cubitermes speciosus

Clostridium mayombei sp. nov., a previously undescribed H₂-oxidizing CO₂-reducing acetogenic bacterium, was isolated from gut contents of the African soilfeeding termite, Cubitermes speciosus. Cells were anaerobic, Gram positive, catalase and oxidase negative, endospore-forming motile rods which measured 1×2 – 6 m and which had a DNA base composition of 25.6 mol% G+C (strain SFC-5). Optimum conditions for growth on H₂+CO₂ were at 33°C and pH 7.3, and under these conditions cells produced acetate according to the equation: 4 H₂+2 CO₂CH₃COOH+2 H₂O. Other substrates supporting good growth included carbohydrates (e.g. glucose, xylose, starch), sugar alcohols, and organic and amino acids, and with these substrates acetate was almost always the principle fermentation product. Comparative analysis of 16S rRNA nucleotide sequences confirmed that C. mayombei was closely related to various members of the genus Clostridium. However, morphological and physiological differences between C. mayombei and other homoacetogenic clostridia were deemed significant enough to warrant creation of a new taxon. Results are discussed in light of the diversity of H₂/CO₂ acetogens recently isolated from various termites, and in terms of the relative importance of H₂/CO₂ acetogenesis to termite nutrition.     

Ruminococcus hydrogenotrophicus sp. nov., a new H2/CO2-utilizing acetogenic bacterium isolated from human feces

A new H₂/CO₂-utilizing acetogenic bacterium was isolated from the feces of a non-methane-excreting human subject. The two strains S5a33 and S5a36 were strictly anaerobic, gram-positive, non-sporulating coccobacilli. The isolates grew autotrophically by metabolizing H₂/CO₂ to form acetate as sole metabolite and were also able to grow heterotrophically on a variety of organic compounds. The major end product of glucose and fructose fermentation was acetate; the strains also formed ethanol, lactate and, to a lesser extent, isobutyrate and isovalerate. The G+C content of DNA of strain S5a33 was 45.2 mol%. 16S rRNA gene sequencing demonstrated that the two acetogenic isolates were phylogenetically identical and represent a new subline within Clostridium cluster XIVa. Based on phenotypic and phylogenetic considerations, a new species, Ruminococcus hydrogenotrophicus, is proposed. The type strain of R. hydrogenotrophicus is S5a33 (DSM 10507). Furthermore, H₂/CO₂ acetogenesis appeared to be a common property of most of the species phylogenetically closely related to strain S5a33 (Clostridium coccoides, Ruminococcus hansenii, and Ruminococcus productus). Received: 11 April 1996 / Accepted: 11 June 1996     

Sporomusa termitida sp. nov., an H2/CO2-utilizing acetogen isolated from termites

H₂-oxidizing CO₂-reducing acetogenic bacteria were isolated from gut contents of Nasutitermes nigriceps termites. Isolates were strictly anaerobic, Gram negative, endospore-forming, straight to slightly curved rods (0.5–0.8×2–8 m) that were motile by means of lateral flagella. Cells were oxidase negative, but catalase positive and possessed a b-type cytochrome(s) associated with the cell membrane. Cells grew anaerobically with H₂+CO₂ as energy source and catalyzed a total synthesis of acetate from this gas mixture. H₂ uptake by a representative isolate (strain JSN-2) displayed a K _m=6 M and V _max=380 nmol x min^-1 x mg protein^-1. Other substrates used as energy sources for growth and acetogenesis included CO, methanol, betaine, trimethoxybenzoate, and various other organic acids. Succinate was also fermented, but propionate was formed from this substrate instead of acetate. Of a variety of sugars and sugar alcohols tested, only mannitol supported growth. Cells grew optimally at 30° C and pH 7.2 and required yeast extract or a source of amino acids (e.g. Casamino acids) for good growth. During initial enrichment and isolation, cells appeared sensitive to various reducing agents commonly employed in media for anaerobes. The DNA base composition of strain JSN-2 was 48.6 mol% G+C. On the bases of cell morphology, substrate utilization spectrum, and DNA base composition, strain JSN-2 is here-with proposed as the type strain of the new species Sporomusa termitida.Journal article no. 12513 from the Michigan Agricultural Experiment Station     

Desulfolutivibrio sulfoxidireducens gen. nov., sp. nov., isolated from a pyrite-forming enrichment culture and reclassification of Desulfovibrio sulfodismutans as Desulfolutivibrio sulfodismutans comb. nov

Two strains of sulfate-reducing bacteria (J.5.4.2-L4.2.8^T and J.3.6.1-H7) were isolated from a pyrite-forming enrichment culture and were compared phylogenetically and physiologically to the closest related type strain Desulfovibrio sulfodismutans DSM 3696^T. The isolated strains were vibrio-shaped, motile rods that stained Gram-negative. Growth occurred from 15 to 37 °C and within a pH range of 6.5–8.5. Both strains used sulfate, thiosulfate, sulfite, and dimethyl sulfoxide (DMSO) as electron acceptor when grown with lactate. Lactate was incompletely oxidized to acetate. Formate and H₂ were used as electron donor in the presence of acetate. Dismutation of thiosulfate and pyrosulfite was observed. The two new isolates differed from D. sulfodismutans by the utilization of DMSO as electron acceptor, 82% genome-wide average nucleotide identity (ANI) and 32% digital DNA-DNA hybridization (dDDH), thus representing a novel species. The type strain of the type species Desulfovibrio desulfuricans Essex6^T revealed merely 88% 16S rRNA gene identity and 49% genome-wide average amino acid identity (AAI) to the new isolates as well as to D. sulfodismutans. Furthermore, the dominance of menaquinone MK-7 over MK-6 and the dominance of ai-C_15:0 fatty acids were observed not only in the two new isolated strains but also in D. sulfodismutans. Therefore, the definition of a new genus is indicated for which the name Desulfolutivibrio is proposed. We propose for strains J.5.4.2-L4.2.8^T and J.3.6.1-H7 the name Desulfolutivibrio sulfoxidireducens gen. nov. sp. nov. with strain J.5.4.2-L4.2.8^T defined as type strain. In addition, we propose the reclassification of Desulfovibrio sulfodismutans as Desulfolutivibrio sulfodismutans comb. nov.     

Acetonema longum gen.nov.sp.nov., an H2/CO2 acetogenic bacterium from the termite,Pterotermes occidentis

A previously undescribed, H₂-oxidizing CO₂-reducing acetogenic bacterium was isolated from gut contents of the wood-feeding termite, Pterotermes occidentis. Cells of representative strain APO-1 were strictly anaerobic, Gram-negative, endospore-forming motile rods which measured 0.30–0.40×6–60 m. Cells were catalase positive, oxidase negative, and had 51.5 mol percent G+C in their DNA. Optimum conditions for growth on H₂+CO₂ were at 30–33°C and pH (initial) 7.8, and under these conditions cells formed acetate according to the equation: 4 H₂+2 CO₂CH₃COOH+2 H₂O. Other energy sources supporting good growth of strain APO-1 included glucose, ribose, and various organic acids. Acetate and butyrate were major fermentation products from most organic compounds tested, however propionate, succinate, and 1,2-propanediol were also formed from some substrates. Based on comparative analysis of 16S rRNA nucleotide sequences, strain APO-1 was related to, but distinct from, members of the genus Sporomusa. Moreover, physiological and morphological differences between strain APO-1 and the six known species of Sporomusa were significant. Consequently, it is proposed herewith that a new genus, Acetonema, be established with strain APO-1 as the type strain of the new species, Acetonema longum. A. longum may contribute to the nutrition of P. occidentis by forming acetate, propionate and butyrate, compounds which are important carbon and energy sources for termites.     

Assessment of Reductive Acetogenesis with Indigenous Ruminal Bacterium Populations and Acetitomaculum ruminis

The objective of this study was to evaluate the role of reductive acetogenesis as an alternative H₂ disposal mechanism in the rumen. H₂/CO₂-supported acetogenic ruminal bacteria were enumerated by using a selective inhibitor of methanogenesis, 2-bromoethanesulfonic acid (BES). Acetogenic bacteria ranged in density from 2.5 × 10⁵ cells/ml in beef cows fed a high-forage diet to 75 cells/ml in finishing steers fed a high-grain diet. Negligible endogenous acetogenic activity was demonstrated in incubations containing ruminal contents, NaH¹³CO₃, and 100% H₂ gas phase since [U-¹³C]acetate, as measured by mass spectroscopy, did not accumulate. Enhancement of acetogenesis was observed in these incubations when methanogenesis was inhibited by BES and/or by the addition of an axenic culture of the rumen acetogen Acetitomaculum ruminis 190A4 (10⁷ CFU/ml). To assess the relative importance of population density and/or H₂ concentration for reductive acetogenesis in ruminal contents, incubations as described above were performed under a 100% N₂ gas phase. Both selective inhibition of methanogenesis and A. ruminis 190A4 fortification (>10⁵ CFU/ml) were necessary for the detection of reductive acetogenesis under H₂-limiting conditions. Under these conditions, H₂ accumulated to 4,800 ppm. In contrast, H₂ accumulated to 400 ppm in incubations with active methanogenesis (without BES). These H₂ concentrations correlated well with the pure culture H₂ threshold concentrations determined for A. ruminis 190A4 (3,830 ppm) and the ruminal methanogen 10-16B (126 ppm). The data demonstrate that ruminal methanogenic bacteria limited reductive acetogenesis by lowering the H₂ partial pressure below the level necessary for H₂ utilization by A. ruminis 190A4.     

New types of acetate-oxidizing,sulfate-reducing Desulfobacter species,D. hydrogenophilus sp. nov., D. latus sp. nov., and D. curvatus sp. nov.

Sulfate-reducing bacteria with oval to rod-shaped cells (strains AcRS1, AcRS2) and vibrio-shaped cells (strains AcRM3, AcRM4, AcRM5) differing by size were isolated from anaerobic marine sediment with acetate as the only electron donor. A vibrio-shaped type (strain AcKo) was also isolated from freshwater sediment. Two strains (AcRS1, AcRM3) used ethanol and pyruvate in addition to acetate, and one strain (AcRS1) grew autotrophically with H₂, sulfate and CO₂. Higher fatty acids or lactate were never utilized. All isolates were able to grow in ammonia-free medium in the presence of N₂. Nitrogenase activity under such conditions was demonstrated by the acetylene reduction test. The facultatively lithoautotrophic strain (AcRS1), a strain (AcRS2) with unusually large cells (2×5 m), and a vibrio-shaped strain (AcRM3) are described as new Desulfobacter species, D. hydrogenophilus, D. latus, and D. curvatus, respectively.     

Anaerobic biodegradation of methyl esters byAcetobacterium woodii andEubacterium limosum

Summary The ability ofAcetobacterium woodii andEubacterium limosum to degrade methyl esters of acetate, propionate, butyrate, and isobutyrate was examined under growing and resting-cell conditions. Both bacteria hydrolyzed the esters to the corresponding carboxylates and methanol under either condition. Methanol was further oxidized to formate under growing but not resting conditions. Unlike the metabolism of phenylmethylethers, no H₂ requirement was evident for ester biotransformation. The hydrolysis of methyl carboxylates is thermodynamically favorable under standard conditions and the mixotrophic metabolism of ester/CO₂ allowed for bacterial growth. These results suggest that the degradation of methyl carboxylates may be a heretofore unrecognized nutritional option for acetogenic bacteria.     

Lithoautotrophic growth of sulfate-reducing bacteria,and description of Desulfobacterium autotrophicum gen. nov., sp. nov.

The capacity of mesophilic sulfate-reducing bacteria to grow lithoautotrophically with H₂, sulfate and CO₂ was investigated with enrichment cultures and isolated species. (a) Enrichments in liquid mineral media with H₂, sulfate and CO₂ consistently yielded mixed cultures of nonautotrophic, acetate-requiring Desulfovibrio species and autotrophic, acetate-producing Acetobacterium species (cell ratio approx. 20:1). (b) By direct dilution of mud samples in agar, various non-sporing sulfate reducers were isolated in pure cultures that did grow autotrophically. Two oval cell types (strains HRM2, HRM4) and one curved cell type (strain HRM6) from marine sediment were studied in detail. The strains grew in mineral medium supplemented only with vitamins (biotin, p-aminobenzoate, nicotinate). Carbon autotrophy was evident (i) from comparative growth experiments with non-autotrophic, acetate-requiring species, (ii) from high cell densities ruling out a cell synthesis from organic impurities in the mineral media, and (iii) by demonstrating that 96–99% of the cell carbon was derived from ¹⁴C-labelled CO₂. Autotrophic growth occurred with a doubling time of 16–20 h at 24–28°C. Formate, fatty acids up to palmitate, ethanol, lactate, succinate, fumarate, malate and other organic acids were also used and completely oxidized. The three strains possessed cytochromes of the b-and c-type, but no desulfoviridin. Strain HRM2 is described as a new species of a new genus, Desulfobacterium autotrophicum. (c) The capacity for autotrophic growth was also tested with sulfate-reducing bacteria that originally had been isolated on organic substrates. The incompletely oxidizing, non-sporing types such as Desulfovibrio and Desulfobulbus species and Desulfomonas pigra were confirmed to be obligate heterotrophs that required acetate for growth with H₂ and sulfate. In contrast, several of the completely oxidizing sulfate reducers were facultative autotrophs, such as Desulfosarcina variabilis, Desulfonema limicola, Desulfococcus niacini, and the newly isolated Desulfobacterium vacuolatum and Desulfobacter hydrogenophilus. The only incompletely oxidizing sulfate reducer that could grow autotrophically was the sporing Desulfotomaculum orientis, which obtained 96% of its cell carbon from ¹⁴C-labelled CO₂. Desulfovibrio baarsii and Desulfococcus multivorans may also be regarded as types of facultative autotrophs; they could not oxidize H₂, but grew on sulfate with formate as the only organic substrate.     

Thermalkalibacillus uzonensis gen. nov. sp. nov, a novel aerobic alkali-tolerant thermophilic bacterium isolated from a hot spring in Uzon Caldera, Kamchatka

A novel thermophilic, alkali-tolerant, and CO-tolerant strain JW/WZ-YB58^T was isolated from green mat samples obtained from the Zarvarzin II hot spring in the Uzon Caldera, Kamchatka (Far East Russia). Cells were Gram-type and Gram stain-positive, strictly aerobic, 0.7–0.8 μm in width and 5.5–12 μm in length and produced terminal spherical spores of 1.2–1.6 μm in diameter with the mother cell swelling around 2 μm in diameter (drumstick-type morphology). Cells grew optimally at pH^25°C 8.2–8.4 and temperature 50–52°C and tolerated maximally 6% (w/v) NaCl. They were strict heterotrophs and could not use either CO or CO₂ (both with or without H₂) as sole carbon source, but tolerated up to 90% (v/v) CO in the headspace. The isolate grew on various complex substrates such as yeast extract, on carbohydrates, and organic acids, which included starch, d-galactose, d-mannose, glutamate, fumarate and acetate. Catalase reaction was negative. The membrane polar lipids were dominated by branched saturated fatty acids, which included iso-15:0 (24.5%), anteiso-15:0 (18.3%), iso-16:0 (9.9%), iso-17:0 (17.5%) and anteiso-17:0 (9.7%) as major constituents. The DNA G+C content of the strain is 45 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain JW/WZ-YB58^T is distantly (<93% similarity) related to members of Bacillaceae. On the basis of 16S rRNA gene sequence, physiological and phenotypic characteristics, the isolate JW/WZ-YB58^T (ATCC BAA-1258; DSM 17740) is proposed to be the type strain for the type species of the new taxa within the family Bacillaceae, Thermalkalibacillus uzoniensis gen. nov. sp. nov. The Genbank accession number for the 16S rRNA gene sequence is DQ221694.The Genbank accession number for the 16S rRNA gene sequence of strain JW/WZ-YB58^T is DQ221694.     

The influence of ruminal concentrations of O2 and CO2 on fermentative metabolism of the rumen entodiniomorphid ciliateEudiplodinium maggii

The effects of ruminal concentrations of CO₂ and O₂ on glucose-stimulated and endogenous fermentation of the rumen ciliateEudiplodinium maggii were investigated. The principal metabolic products were butyrate, acetate, lactate, propionate, H₂, and CO₂.¹³C NMR spectroscopy revealed glycerol to be an important, but previously unidentified, fermentation product of this organism. Glucose uptake and metabolite formation rates were influenced by the headspace composition during protozoal incubations. Glucose uptake was most rapid in the presence of low O₂ in N₂ (1–3 µM O₂ dissolved in the protozoal suspension). Pathways located in the hydrogenosomes were O₂ sensitive, and low O₂ concentrations resulted in lowered acetate, H₂, and CO₂ formation. The presence of high CO₂ (65% gaseous headspace by volume) resulted in elevated acetate and butyrate formation; fumarate and propionate were similarly found to accumulate at higher concentration than previously detected in the supernatants. Results suggest that under conditions similar to those prevailing in the rumen (i.e., high CO₂),Eu. maggii produces higher levels of important ruminal volatile fatty acids, and thus its relative contribution to rumen metabolism may have been underestimated.     

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids II. Incomplete oxidation of propionate by Desulfobulbus propionicus gen. nov., sp. nov.

A new type of sulfate-reducing bacteria with ellipsoidal to lemon-shaped cells was regularly enriched from anaerobic freshwater and marine mud samples when mineral media with propionate and sulfate were used. Three strains (1pr3, 2pr4, 3pr10) were isolated in pure culture. Propionate, lactate and alcohols were used as electron donors and carbon sources. Growth on H₂ required acetate as a carbon source in the presence of CO₂. Stoichiometric measurements revealed that oxidation of propionate was incomplete and led to acetate as an endproduct. Instead of sulfate, strain 1pr3 was shown to reduce sulfite and thiosulfate to H₂S; nitrate also served as electron acceptor and was reduced to ammonia. With lactate or pyruvate, all three strains were able to grow without external electron acceptor and formed propionate and acetate as fermentation products. None of the strains contained desulfoviridin. In strain 1pr3 cytochromes of the b- and c-type were identified. Strain 1pr3 is described as type strain of the new species and genus, Desulfobulbus propionicus.     

Treponema bryantii sp. nov., a rumen spirochete that interacts with cellulolytic bacteria

A saccharolytic spirochete that associated and interacted with cellulolytic bacteria was isolated from bovine rumen fluid. Isolation was accomplished by means of a procedure involving serial dilution of a sample of rumen fluid into a cellulose-containing agar medium. Clear zones appeared within the medium as a result of cellulose hydrolysis by rumen bacteria. The saccharolytic spirochete and a cellulolytic bacterium later identified as a strain of Bacteroides succinogenes were isolated from the clear zones. The spirochete did not utilize cellulose, but grew in coculture with the cellulolytic bacterium in cellulose-containing media. When cocultured in these media the spirochete used, as fermentable substrates, soluble sugars released from cellulose by the cellulolytic bacterium. In cellulosecontaining agar medium the spirochete enhanced cellulose breakdown by the B. succinogenes strain. Electron microscopy showed that the helical spirochete cells possessed an outer sheath, a protoplasmic cylinder, and two periplasmic fibrils. Under a CO₂ atmosphere, in a reduced medium containing inorganic salts, rumen fluid, glucose, and NaHCO₃, the spirochete grew to a final density of 1.9×10⁹ cells/ml. Succinate, acetate, and formate were products of the fermentation of glucose by growing cells. CO₂ (HCO₃ ^-), branched short-chain fatty acids, folic acid, biotin, niacinamide, thiamine, pyridoxal, and a carbohydrate were required for growth of the spirochete. The results of this study indicated that the rumen spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema bryantii.Abbreviations cpm counts per minute - GC guanine plus cytosine - T_m melting temperature - PC protoplasmic cylinder - PF pertplasmic fibrils (axial fibrils) - OS outer sheath - ID insertion disk     

Syntrophococcus sucromutans sp. nov. gen. nov. uses carbohydrates as electron donors and formate,methoxymonobenzenoids or Methanobrevibacter as electron acceptor systems

Most probable number (MPN) estimates indicated that a mean of 4.3×10⁷ and 5×10⁶ bacteria per ml of rumen fluid from a predominantly alfalfa hay-fed steer demethoxylated ferulate and syringate, respectively. After further enrichment from an MPN tube of the highest dilution showing demethoxylation of syringate, strain S195 was isolated using roll tubes with syringate as an added energy source. S195 was an anaerobic, Gram-negative, nonmotile coccus, 1 to 1.3 m in diameter, and was unique in using various carbohydrates as electron donor with acetate as the sole organic product. One of the following electron acceptor systems allowed growth (organic products in parentheses): Methanobrevibacter simithii (CH₄), formate (acetate), 3,4,5-trimethoxybenzoate and syringate (acetate and gallate), vanillate (acetate and protocatechuate), vanillin (acetate, protocatechuic aldehyde and protocatechuate), ferulate (acetate, caffeate and hydrocaffeate), caffeate (hydrocaffeate). Strain S195 required 30% (v/v) rumen fluid in the medium for good growth. S195 was placed in a new genus and species, Syntrophococcus sucromutans, of the family Veillonellaceae.Abbreviations G+C Guanine plus cytosine - MPN most probable number - OD optical density     

A new H2 / CO2-using acetogenic bacterium from the rumen: Description of Ruminococcus schinkii sp. nov.

Abstract Two strains of H2 / CO2-using acetogenic bacteria were isolated from the rumen of suckling lambs. Both strains displayed a coccobacillar morphology and possessed a Gram-positive type cell wall. Numerous organic substrates, including some O-methylated aromatic compounds, were used heterotrophically. 16S rRNA gene sequencing demonstrated that the two acetogenic isolates were phylogenetically identical and represent a new subline within Clostridium cluster XIVa. Based on phenotypic and phylogenetic considerations a new species, Ruminococcus schinkii sp. nov., is proposed.