Desulfuromonas palmitatis sp. nov., a marine dissimilatory Fe(III) reducer that can oxidize long-chain fatty acids

Studies on the microorganisms living in hydrocarbon-contaminated sediments in San Diego Bay, California led to the isolation of a novel Fe(III)-reducing microorganism. This organism, designated strain SDBY1, was an obligately anaerobic, non-motile, non-flagellated, gram-negative rod. Strain SDBY1 conserves energy to support growth from the oxidation of acetate, lactate, succinate, fumarate, laurate, palmitate, or stearate. H₂ was also oxidized with the reduction of Fe(III), but growth with H₂ as the sole electron donor was not observed. In addition to various forms of soluble and insoluble Fe(III), strain SDBY1 also coupled growth to the reduction of fumarate, Mn(IV), or S⁰. Air-oxidizedminus dithionite-reduced difference spectra exhibited peaks at 552.8, 523.6, and 422.8 nm, indicative ofc-type cytochrome(s). Strain SDBY1 shares physiological characteristics with organisms in the generaGeobacter, Pelobacter, andDesulfuromonas. Detailed analysis of the 16S rRNA sequence indicated that strain SDBY1 should be placed in the genusDesulfuromonas. The new species nameDesulfuromonas palmitatis is proposed.D. palmitatis is only the second marine organism found (afterD. acetoxidans) to oxidize multicarbon organic compounds completely to carbon dioxide with Fe(III) as an electron acceptor and provides the first pure culture model for the oxidation of long-chain fatty acids coupled to Fe(III) reduction.     

Propionate-Degrading Bacterium, Syntrophobacter wolinii sp. nov. gen. nov., from Methanogenic Ecosystems

A new genus and species of a nonmotile gram-negative rod, Syntrophobacter wolinii, is the first bacterium described which degrades propionate only in coculture with an H₂-using organism and in the absence of light or exogenous electron acceptors such as O₂, sulfate, or nitrate. It was isolated from methanogenic enrichments from an anaerobic municipal sewage digestor, using anaerobic roll tubes containing a medium with propionate as the energy source in association with an H₂-using, sulfate-reducing Desulfovibrio sp. which cannot utilize fatty acids other than formate. S. wolinii produced acetate and, presumably, CO₂ and H₂ (or formate) from propionate. In media without sulfate and with Methanospirillum hungatei, a methanogen that uses only H₂-CO₂ or formate as an energy source, acetate, methane, and, presumably, CO₂ were produced from propionate and only small amounts of Desulfovibrio sp. were present. Isolation in coculture with the methanogen was not successful. S. wolinii does not use other saturated fatty acids as energy sources.     

Desulfotomaculum geothermicum sp. nov., a thermophilic,fatty acid-degrading,sulfate-reducing bacterium isolated with H2 from geothermal ground water

A strictly anaerobic, thermophilic, fatty acids-degrading, sporulating sulfate-reducing bacterium was isolated from geothermal ground water. The organism stained Gram-negative and formed gas vacuoles during sporulation. Lactate, ethanol, fructose and saturated fatty acids up to C₁₈ served as electron donors and carbon sources with sulfate as external electron acceptor. Benzoate was not used. Stoichiometric measurements revealed a complete oxidation of part of butyrate although growth with acetate as only electron donor was not observed. The rest of butyrate was oxidized to acetate. The strain grew chemolithoautotrophically with hydrogen plus sulfate as energy source and carbon dioxide as carbon source without requirement of additional organic carbon like acetate. The strain contained a c-type cytochrome and presumably a sulfite reductase P582. Optimum temperature, pH and NaCl concentration for growth were 54°C, pH 7.3–7.5 and 25 to 35 g NaCl/l. The G+C content of DNA was 50.4 mol %. Strain BSD is proposed as a new species of the spore-forming sulfate-reducing genus Desulfotomaculum, D. geothermicum.     

Psychromonas antarcticus gen. nov., sp. nov., a new aerotolerant anaerobic, halophilic psychrophile isolated from pond sediment of the McMurdo Ice Shelf, Antarctica

A gram-negative, rod- to oval-shaped, aerotolerant anaerobic bacterium was isolated from an anaerobic enrichment inoculated with sediment taken from below the cyanobacterial mat of a high-salinity pond near Bratina Island on the McMurdo Ice Shelf, Antarctica. The organism was positive for terminal oxidase and catalase and was motile by means of a polar flagellum. Optimal growth of anaerobic cultures occurred at 12° C, at pH 6.5, and at an NaCl concentration of 3% (w/v). Of a variety of polysaccharides tested, only starch and glycogen supported growth. No growth was observed on cellulosic substrates and xylan, and the organism was unable to attack esculin. Monosaccharides and disaccharides, including the cyanobacterial cell-wall constituent N-acetyl glucosamine, were fermented. Per 100 mol of hexose, the following products (in mol) were formed: acetate, 60; formate, 130; ethanol, 56; lactate, 73; CO₂, 15; and butyrate, 2. Propionate, ethanol, n-propanol, n-butanol and succinate were not detectable in the culture medium (< 1 mol per 100 mol of monomer). Hydrogen was not detected in the head space (detection limit < 10^–5 atm). Growth yields in aerobic static liquid cultures were slightly higher than those in anaerobic culture, and fermentation favoured acetate at the expense of electron sink products. Growth was inhibited in aerobic shaking cultures, and the organism did not utilize nitrate or sulfate as electron acceptors. The G+C content of the DNA from the bacterium was 42.8 mol%. A phylogenetic analysis indicated that the organism is a member of the γ-subgroup of Proteobacteria, but that it is distinct from other members of this group based on the sequence of its 16S rRNA gene, mol% G+C, morphology, and physiological and biochemical characteristics. It is designated as a new genus and species; the type strain is star-1 (DSM 10704). Received: 17 June 1996 / Accepted: 13 October 1997     

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     

Anaerobic degradation of acetone by Desulfococcus biacutus spec. nov.

From anaerobic digestor sludge of a waste water treatment plant, a gram-negative, strictly anaerobic sulfate-reducing bacterium was isolated with acetone as sole organic substrate. The bacterium was characterized as a new species, Desulfococcus biacutus. The strain grew with acetone with doubling times of 72 h to 120 h; the growth yield was 12.0 (±2.1) g · [mol acetone]^-1. Acetone was oxidized completely, and no isopropanol was formed. In labelling studies with ¹⁴CO₂, cell lipids (including approx. 50% PHB) of acetone-grown cells became labelled 7 times as high as those of 3-hydroxy-buyrate-grown cells. Enzyme studies indicated that acetone was degraded via acetoacetyl-CoA, and that acetone was channeled into the intermediary metabolism after condensation with carbon dioxide to a C₄-compound, possibly free acetoacetate. Acetoacetyl-CoA is cleaved by a thiolase reaction to acetyl-CoA which is completely oxidized through the carbon monoxide dehydrogenase pathway. Strain KMRActS was deposited with the Deutsche Sammlung von Mikroorganismen, Braunschweig, under the number DSM 5651.     

Zymobacter palmae gen. nov., sp. nov., a new ethanol-fermenting peritrichous bacterium isolated from palm sap

Zymobacter palmae gen. nov., sp. nov. was proposed for a new ethanol-fermenting bacterium that was isolated from palm sap in Okinawa Prefecture, Japan. The bacterium is gram-negative, facultatively anaerobic, catalase-positive, oxidase-negative, nonspore-forming and peritrichously flagellated. It requires nicotinic acid for growth. It ferments hexoses, -linked di- and tri-saccarides, and sugar alcohols (fructose, galactose, glucose, mannose, maltose, melibiose, saccharose, raffinose, mannitol and sorbitol). Fifteen percent of maltose in broth medium is effectively fermented, whereas glucose with a concentration higher than 10% delayed growth initiation and decreased growth rates. Maltose is fermented to produce ethanol and CO₂ with a trace amount of acids. Approximately 2 mol of ethanol are produced from 1 mol moiety of hexose of maltose. The organism possesses ubiquinone-9. The G+C content of the DNA is 55.8+-0.4 mol%. Major cellular fatty acids were palmitic and oleic acids and cyclopropanic acid of C_19:0. Characteristic hydroxylated acid was 3-hydroxy dodecanoic acid. The bacterium is distinct from other ethanol-fermenting bacteria belonging to the genera Zymomonas Kluyver and van Niel 1936 and Saccharobacter Yaping et al. 1990 with respect to chemotaxonomic and other phenotypic characters to warrant to compose a new genus and a new species. The type strain is strain T109 (= IAM 14233).Abbreviation IAM IAM Culture Collection, Institute of Applied Microbiology. The University of Tokyo     

Syntrophomonas wolfei gen. nov. sp. nov., an Anaerobic, Syntrophic, Fatty Acid-Oxidizing Bacterium

An anaerobic, nonphototrophic bacterium that β-oxidizes saturated fatty acids (butyrate through octanoate) to acetate or acetate and propionate using protons as the electron acceptor (H₂ as electron sink product) was isolated in coculture with either a non-fatty acid-degrading, H₂-utilizing Desulfovibrio sp. or methanogens. Three strains of the bacterium were characterized and are described as a new genus and species, Syntrophomonas wolfei. S. wolfei is a gram-negative, slightly helical rod with round ends that possesses between two to eight flagella laterally inserted along the concave side of the cell. It has a multilayered cell wall of the gram-negative type. The presence of muramic acid, inhibition of growth by penicillin, and increased sensitivity of the cells to lysis after treatment with lysozyme indicate that peptidoglycan is present in the cell wall. Cells of S. wolfei contain poly-β-hydroxybutyrate. Isoheptanoate was degraded to acetate, isovalerate, and H₂. Carbohydrates, proteinaceous materials, alcohols, or other tested organic compounds do not support growth. Common electron acceptors are not utilized with butyrate as the electron donor. Growth and degradation of fatty acids occur only in syntrophic association with H₂-using bacteria. The most rapid generation time obtained by cocultures of S. wolfei with Desulfovibrio and Methanospirillum hungatei is 54 and 84 h, respectively. The addition of Casamino Acids but neither Trypticase nor yeast extract stimulated growth and resulted in a slight decrease in the generation time of S. wolfei cocultured with M. hungatei. The addition of H₂ to the medium stopped growth and butyrate degradation by S. wolfei.     

Sporomusa,a new genus of gram-negative anaerobic bacteria including Sporomusa sphaeroides spec. nov. and Sporomusa ovata spec. nov.

A new genus of strictly anaerobic, gram-negative, banana-shaped bacteria is described. Cells formed spores and were motile by means of up to 15 laterally inserted flagella. Nitrate or sulfate were not used as electron acceptor. Organic substrates that were fermented included N-methyl compounds, such as betaine, N,N-dimethylglycine and sarcosine, primary alcohols, hydroxy fatty acids, and 2,3-butanediol. In addition, molecular hydrogen and carbon dioxide were fermented to acetate. The latter was the characteristic fermentation product in general. During growth on betaine, trimethylamine was formed in addition. The degradation of N,N-dimethylglycine yielded acetate, monomethylamine, and trimethylamine. The presence of cytochrome b and of ubiquinone in the cells was shown. The deoxyribonuleic acid base composition of the strains was between 41.3 and 47.4 mol% guanine plus cytosine. The name Sporomusa is proposed for this new genus. On the basis of the DNA-DNA homology values obtained, the shape of the spores and some other properties, the isolated strains were assigned to two species. Names proposed: Sporomusa sphaeroides and Sporomusa ovata. The type species is S. sphaeroides and the type strains are strain E, DSM 2875 (S. sphaeroides) and strain H1, DSM 2662 (S. ovata).Dedicated to Prof. H. G. Schlegel on the occasion of his 60th birthday     

Characterization of Aquamicrobium defluvii gen. nov. sp. nov., a thiophene-2-carboxylate-metabolizing bacterium from activated sludge

A gram-negative bacterium was isolated from activated sewage sludge with thiophene-2-carboxylate as the sole source of carbon and with nitrate as an electron acceptor. The isolate, strain NKK, was a motile, oxidase- and catalase-positive, rod-like bacterium with a G+C content of 61.7 mol%. Besides nitrate, oxygen could serve as a terminal electron acceptor. Among many carbon sources tested, only a few sugars, fatty acids, and thiophene-2-carboxylate supported growth. Other heterocyclic compounds were not used. The sulfur atom of thiophene-2-carboxylate was oxidized to thiosulfate when cells were grown aerobically, or to elemental sulfur when cells were grown anaerobically with nitrate. Nitrate was reduced to nitrite. Growth on thiophene-2-carboxylate was dependent on the addition of molybdate to the medium. Tungstate, a specific antagonist of molybdate, inhibited growth on thiophene-2-carboxylate at concentrations > 10^–7 M. Three inducible enzymes involved in the metabolism of thiophene-2-carboxylate were detected: an ATP-, CoA-, thiophene-2-carboxylate- and Mg²⁺-dependent thiophene-2-carboxyl-CoA ligase (AMP-forming), a molybdenum-containing thiophene-2-carboxyl-CoA dehydrogenase, and a thiophene-2-carboxyl-CoA thioesterase. The sequence of the 16S rRNA gene suggested a classification of strain NKK within the α-subgroup of the Proteobacteria as a new genus and species, Aquamicrobium defluvii gen. nov. sp. nov. (DSM 11603), closely related to Mesorhizobium sp. and Phyllobacterium sp., but representing a distinct lineage equal in depth to those of the two mentioned genera. Aquamicrobium defluvii can be distinguished from both genera by a distinct spectrum of substrates, the maximal growth temperature, and a different salt tolerance. Received: 8 September 1997 / Accepted: 14 November 1997     

Syntrophus aciditrophicus sp. nov., a new anaerobic bacterium that degrades fatty acids and benzoate in syntrophic association with hydrogen-using microorganisms

Strain SB^T is a new, strictly anaerobic, gram-negative, nonmotile, non-sporeforming, rod-shaped bacterium that degrades benzoate and certain fatty acids in syntrophic association with hydrogen/formate-using microorganisms. Strain SB^T produced approximately 3 mol of acetate and 0.6 mol of methane per mol of benzoate in coculture with Methanospirillum hungatei strain JF1. Saturated fatty acids, some unsaturated fatty acids, and methyl esters of butyrate and hexanoate also supported growth of strain SB^T in coculture with Desulfovibrio strain G11. Strain SB^T grew in pure culture with crotonate, producing acetate, butyrate, caproate, and hydrogen. The molar growth yield was 17 ± 1 g cell dry mass per mol of crotonate. Strain SB^T did not grow with fumarate, iron(III), polysulfide, or oxyanions of sulfur or nitrogen as electron acceptors with benzoate as the electron donor. The DNA base composition of strain SB^T was 43.1 mol% G+C. Analysis of the 16 S rRNA gene sequence placed strain SB^T in the δ-subdivision of the Proteobacteria, with sulfate-reducing bacteria. Strain SB^T was most closely related to members of the genus Syntrophus. The clear phenotypic and genotypic differences between strain SB^T and the two described species in the genus Syntrophus justify the formation of a new species, Syntrophus aciditrophicus. Received: 2 June 1998 / Accepted: 16 November 1998     

Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra- and trichloroethene in an anaerobic respiration

The highly enriched anaerobic bacterium that couples the reductive dechlorination of tetrachloroethene to growth, previously referred to as PER-K23, was obtained in pure culture and characterized. The bacterium, which does not form spores, is a small, gram-negative rod with one lateral flagellum. It utilized only H₂ as an electron donor and tetrachloroethene and trichloroethene as electron acceptors in an anaerobic respiration process; it could not grow fermentatively. Acetate served as a carbon source in a defined medium containing iron as the sole trace element, the two vitamins thiamine and cyanocobalamin, and the three amino acids arginine, histidine, and threonine. The cells contained menaquinones and b-type cytochromes. The G+C content of the DNA was 45.3 ± 0.3 mol%. The cell wall consisted of type-A3γ peptidoglycan with ll-diaminopimelic acid and one glycine as an interpeptide bridge. The cells are surrounded by an S-layer; an outer membrane was absent. Comparative sequence analysis of the 16S rRNA sequence showed that PER-K23 is related to gram-positive bacteria with a low G+C content of the DNA. Based on the cytological, physiological, and phylogenetic characterization, it is proposed to affiliate the isolate to a new genus, Dehalobacter, with PER-K23 as the type strain of the new species Dehalobacter restrictus. Received: 14 July 1997 / Accepted: 27 November 1997     

Anaerobic oxidation of fatty acids by Clostridium bryantii sp. nov., a sporeforming,obligately syntrophic bacterium

From marine and freshwater mud samples strictly anaerobic, Gram-positive, sporeforming bacteria were isolated which oxidized fatty acids in obligately syntrophic association with H₂-utilizing bacteria. Even-numbered fatty acids with up to 10 carbon atoms were degraded to acetate and H₂, odd-numbered fatty acids with up to 11 carbon atoms including 2-methylbutyrate were degraded to acetate, propionate and H₂. Neither fumarate, sulfate, thiosulfate, sullur, nor nitrate were reduced. A marine isolate, strain CuCal, is described as type strain of a new species, Clostridium bryantii sp. nov.     

Fermentation of 2,3-butanediol by Pelobacter carbinolicus sp. nov. and Pelobacter propionicus sp. nov., and evidence for propionate formation from C2 compounds

From anaerobic enrichments with 2,3-butanediol as sole substrate pure cultures of new Gram-negative, strictly anaerobic, non-sporeforming bacteria were isolated. Similar isolates were obtained with acetoin as substrate. From marine muds in saltwater medium a short rod (strain Gra Bd 1) was isolated which fermented butanediol, acetoin and ethylene glycol to acetate and ethanol. The DNA base ratio of this strain was 52.3 mol% guanine plus cytosine.From freshwater sediments and sewage sludge, a different type of short rod (strain Ott Bd 1) was isolated in freshwater medium, which fermented butanediol, acetoin, ethanol, lactate and pyruvate stoichiometrically to acetate and propionate. Propanol and butanol were oxidized to the respective fatty acids with concomitant reduction of acetate and bicarbonate to propionate. The DNA base ratio of strain Ott Bd 1 was 57.4 mol% guanine plus cytosine. No other substrates were used by the isolates, and no other products could be detected. In cocultures with Acetobacterium woodii or Methanospirillum hungatei, strain Gra Bd 1 also grew on ethanol, propanol, and butanol by fermenting these alcohols to the respective fatty acids and molecular hydrogen. Cytochromes could not be detected in any of the new isolates. Since both types of bacteria can not be affiliated to any of the existing genera and species, the new species Pelobacter carbinolicus and Pelobacter propionicus are proposed. The mechanism of butanediol degradation and propionate formation from acetate as well as the ecological importance of both processes are discussed.     

Complete oxidation of catechol by the strictly anaerobic sulfate-reducing Desulfobacterium catecholicum sp. nov.

From an anaerobic enrichment culture with vanillate as substrate, a catechol-degrading lemon-shaped nonsporing sulfate-reducing bacterium, strain NZva20, was isolated in pure culture. Growth occurred in defined, bicarbonate-buffered, sulfide-reduced freshwater medium with catechol as sole electron donor and carbon source. Catechol was completely oxidized to CO₂ with an average growth yield of 31 g cell dry mass per mol of catechol, corresponding to 9.5 g cell dry mass per mol of sulfate reduced. Further substrates utilized as electron donors and carbon sources were resorcinol, hydroquinone, benzoate and several other aromatic compounds, hydrogen plus carbon dioxide, formate, lactate, pyruvate, alcohols including methanol, dicarboxylic acids, acetate, propionate and higher fatty acids up to 18 carbon atoms. Instead of sulfate, sulfite, thiosulfate, dithionite or nitrate served as electron acceptors. Nitrate was reduced to ammonium. Strain NZva20 is the first bacterium in which the complete oxidation of organic substrates is linked to the ammonification of nitrate. Elemental sulfur was not utilized as electron acceptor. In the absence of an electron acceptor slow growth occurred on pyruvate or fumarate. The G+C content of the DNA of strain NZva20 was 52.4 mol%. Cytochromes were present. Desulfoviridin could not be detected. Strain NZva20 is described as type strain of a new species, Desulfobacterium catecholicum sp. nov.Affectionately dedicated to Professor Ralph S. Wolfe on the occassion of his 65th birthday     

Isolation and characterization of Dehalospirillum multivorans gen. nov., sp. nov., a tetrachloroethene-utilizing,strictly anaerobic bacterium

A strictly anaerobic bacterium dechlorinating tetrachloroethene (perchloroethylene, PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) was isolated from activated sludge with pyruvate plus PCE as energy substrates. The organism, called Dehalospirillum multivorans, is a gram-negative spirillum that does not form spores. The G+C content of the DNA was 41.5 mol%. According to 16S rRNA gene sequence analysis, D. multivorans represents a new genus and a new species belonging to the epsilon subdivision of Proteobacteria. Quinones, cytochromes b and c, and corrinoids were extracted from the cells. D. multivorans grew in defined medium with PCE and H₂ as sole energy sources and acetate as carbon source; the growth yield under these conditions was 1.4g of cell protein per mol chloride released. Alternatively to PCE, fumarate and nitrate could serve as electron acceptors; sulfate could not replace fumarate, nitrate, or PCE in this respect. In addition to H₂, the organism utilized a variety of electron donors for dechlorination (pyruvate, lactate, ethanol, formate, glycerol). Upon growth on pyruvate plus PCE, the main fermentation products formed were acetatc, lactate, DCE, and H₂. At optimal pH (7.3–7.6) and temperature (30°C), and in the presence of pyruvate (20mM) and PCE (160M), a dechlorination rate of about 50 nmol min^-1 (mg cell protein)^-1 and a doubling time of about 2.5h were obtained with growing cultures. The ability to reduce PCE to DCE appears to be constitutive under the experimental conditions applied since cultures growing in the absence of PCE for several generations immediately started dechlorination when transferred to a medium containing PCE. The organism may be useful for bioremediation of environments polluted with tetrachloroethene.Abbreviations PCE Perchloroethylene, tetrachloroethene - TCE Trichloroethene - DCE cis-1,2-Dichloroethene - CHC Chlorinated hydrocarbon     

THE BIOGENESIS OF MITOCHONDRIA : III. The Lipid Composition of Aerobically and Anaerobically Grown Saccharomyces cerevisiae as Related to the Membrane Systems of the Cells

The growth conditions known to influence the occurrence of mitochondrial profiles and other cell membrane systems in anaerobic cells of S. cerevisiae have been examined, and the effect of the several growth media on the lipid composition of the organism has been determined. The anaerobic cell type containing neither detectable mitochondrial profiles nor the large cell vacuole may be obtained by the culture of the organism on growth-limiting levels of the lipids, ergosterol, and unsaturated fatty acids. Under these conditions, the organism has a high content of short-chain saturated fatty acids (10:0, 12:0), phosphatidyl choline, and squalene, compared with aerobically grown cells, and it is especially low in phosphatidyl ethanolamine and the glycerol phosphatides (phosphatidyl glycerol + cardiolipin). The high levels of unsaturated fatty acids normally found in the phospholipids of the aerobic cells are largely replaced by the short-chain saturated acids, even though the phospholipid fraction contains virtually all of the small amounts of unsaturated fatty acid present in the anaerobic cells. Such anaerobic cells may contain as little as 0.12 mg of ergosterol per g dry weight of cells while the aerobic cells contain about 6 mg of ergosterol per g dry weight. Anaerobic cell types containing mitochondrial profiles can be obtained by the culture of the organism in the presence of excess quantities of ergosterol and unsaturated fatty acids. Such cells have increased levels of total phospholipid, ergosterol, and unsaturated fatty acids, although these compounds do not reach the levels found in aerobic cells. The level of ergosterol in anaerobic cells is markedly influenced by the nature of the carbohydrate in the medium; those cells grown on galactose media supplemented with ergosterol and unsaturated fatty acids have well defined mitochondrial profiles and an ergosterol content (2 mg per g dry weight of cells) three times that of equivalent glucose-grown cells which have poorly defined organelle profiles. Anaerobic cells which are low in ergosterol synthesize increased amounts of squalene.     

Halonatronum saccharophilum gen. nov. sp. nov.: A New Haloalkaliphilic Bacterium of the Order Haloanaerobiales from Lake Magadi

A new alkaliphilic and moderately halophilic chemoorganotrophic anaerobic bacterium (strain Z-7986), which is spore-forming, rod-shaped, and has a gram-negative cell wall pattern, was isolated from the coastal lagoon mud of the highly mineralized Lake Magadi (Kenya). The organism is an obligatorily carbonate- and sodium chloride-dependent motile peritrichously flagellated rod that grows within a 3–17% NaCl concentration range (with an optimum at 7–12% NaCl) and within a pH range of 7.7–10.3 (with an optimum at pH values of 8–8.5). It is a moderate thermophile with a broad temperature optimum at 36–55°C; maximum growth temperature is 60°C. The bacterium catabolizes glucose, fructose, sucrose, maltose, starch, glycogen, N-acetyl-D-glucosamine, and, to a slight degree, peptone and yeast extract. Its anabolism requires yeast extract or casamino acids. Glucose fermentation yields formate, acetate, ethanol, H₂, and CO₂. The bacterium is sulfide-tolerant and capable of the nonspecific reduction of S⁰ to H₂S. The G+C content of the DNA is 34.4 mol %. The analysis of the 16S rRNA sequence revealed that strain Z-7986 belongs to the order Haloanaerobiales and represents a new genus in the family Halobacteroidaceae. We suggest the name Halonatronum saccharophilum gen. nov. sp. nov. The type strain of this species is Z-7986^T (= DSM13868, = Uniqem*211).     

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.