Lipid-phase transitions of the strictly anaerobic bacteria Veillonella parvula and Anaerovibrio lipolytica.
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As a basis for physicochemical studies on the membranes of the strictly anaerobic bacteria Veillonella parvula, Anaerovibrio lipolytica, and Megasphaera elsdenii, the fatty acyl and alk-1-enyl moieties on the phosphoglycerides of these organism were characterized. Uncommon is the high proportion of a heptadecenoic acyl and alk-1-enyl moiety in these three lactate-fermenting bacteria. In contrast to V. parvula and A. lipolytica, M. elsdenii contains high amounts of branched-chain acyl and alk-1-enyl moieties. Freeze-etching electron microscopy showed that the lipids of the plasma membranes of V. parvula and A. lipolytica go from the liquid crystalline to the gel state upon lowering of the temperature, indicating that the membrane lipids are predominantly in the fluid state. No lipid-protein segregation could be detected in the plasma membrane of M. elsdenii. This can be explained by the abundance of branched-chain fatty acyl and alk-1-enyl residues in the membranes of this organism which may prevent lipid-protein segregation during the lipid-phase transition. (+info)
Anaeroglobus geminatus gen. nov., sp. nov., a novel member of the family Veillonellaceae.
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A hitherto unknown anaerobic coccus isolated from a post-operative fluid collection was characterized by phenotypic and phylogenetic methods. 16S rDNA sequence analysis revealed an affiliation of this isolate to the family Veillonellaceae. Also, a high level of sequence similarity was observed to some oral clone sequences of Megasphaera spp. contained in the GenBank database under designations BB166, CS025 and BS073. These clones and the unknown bacterium form a well-separated phylogenetic branch that may represent a novel lineage within the family Veillonellaceae. Based on phenotypic and phylogenetic evidence, a new genus, Anaeroglobus gen. nov., is proposed for the unknown bacterium, with one species, Anaeroglobus geminatus gen. nov., sp. nov. The type strain of Anaeroglobus geminatus is strain AIP 313.00T (= CIP 106856T = CCUG 44773T). It is also suggested that the oral clones BB166, CS025 and BS073 belong to the genus Anaeroglobus. (+info)
Sporomusa aerivorans sp. nov., an oxygen-reducing homoacetogenic bacterium from the gut of a soil-feeding termite.
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Previously undescribed, homoacetogenic bacteria were isolated from gut homogenates of the soil-feeding termite Thoracotermes macrothorax. The isolates were slightly curved, banana-shaped rods (0.6-0.7x1.3-7.0 micro m) and were motile by one or more lateral flagella. In older cultures, cells formed club-like sporangia that developed into terminal, heat-resistant endospores. Cells stained Gram-positive but were Gram-negative in the KOH test. The isolates were mesophilic and grew homoacetogenically on H(2)/CO(2) and L-lactate. Strain TmAO3(T), which was characterized further, also grew homoacetogenically on pyruvate, citrate, L-alanine, D-mannitol, ethanol, formate and methanol. Succinate was decarboxylated to propionate; fumarate, L-malate and oxaloacetate were fermented to propionate and acetate. Hexoses were not used as substrates. Resting cells had a large capacity for hydrogen-dependent oxygen reduction [826 nmol min(-1) (mg protein)(-1)], which enabled them to initiate growth in non-reduced basal medium that originally contained up to 1.5 kPa oxygen in the headspace, although growth commenced only after the medium had been rendered anoxic. Redox difference spectra of cell extracts indicated the presence of membrane-bound b-type cytochrome(s). Comparative 16S rRNA gene sequence analysis revealed that strain TmAO3(T) belongs to a subgroup of the phylum of Gram-positive bacteria that is characterized by low DNA G+C content and a Gram-negative cell wall. It is related most closely to representatives of the genus SPOROMUSA: Based on morphological and physiological properties and on 16S rRNA gene sequence similarity of 94-97 % to other Sporomusa species, the isolates are assigned to Sporomusa aerivorans sp. nov. (type strain, TmAO3(T)=DSM 13326(T)=ATCC BAA-625(T)). (+info)
Rapid screening of Veillonella by ultraviolet fluorescence.
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Among 51 strains of anaerobic gram-negative cocci belonging to the family Veillonellaceae, all strains of Veillonella (V. parvula and V. alcalescens) displayed red fluorescence under long-wave (366 nm) ultraviolet light, whereas no Acidaminococcus or Megasphaera demonstrated fluorescence. In contrast to Bacteroides melaninogenicus, growth of Veillonella does not require hemin and menadione, and flourescence is rapidly lost upon exposure to air. The fluorescent component of a strain of V. parvula examined could not be extracted in solution with water, ether, methanol, or chloroform, but was readily extracted with 0.4 N NaOH. Spectrophotofluorometrically, the fluorescence maximum of this extract was 660 nm with an excitation maximum of 300 nm, when measured at pH 7.2 and 25 C. Coupled with the Gram stain, ultraviolet fluorescence may be a useful tool for rapid screening of Veillonella and is particularly helpful for detection and, isolation of this organism from mixed culture. (+info)
Purification of electron-transferring flavoprotein from Megasphaera elsdenii and binding of additional FAD with an unusual absorption spectrum.
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Electron-transferring flavoprotein (ETF), its redox partner flavoproteins, i.e., D-lactate dehydrogenase and butyryl-CoA dehydrogenase, and another well-known flavoprotein, flavodoxin, were purified from the same starting cell paste of an anaerobic bacterium, Megasphaera elsdenii. The purified ETF contained one mol FAD/mol ETF as the sole non-protein component and bound almost one mol of additional FAD. This preparation is a better subject for investigations of M. elsdenii ETF than the previously isolated ETF, which contains varying amounts of FAD and varying percentages of modified flavins such as 6-OH-FAD and 8-OH-FAD. The additionally bound FAD shows an anomalous absorption spectrum with strong absorption around 400 nm. This spectral change is not due to a chemical modification of the flavin ring because the flavin released by KBr or guanidine hydrochloride is normal FAD. It is also not due to unknown small molecules because the same spectrum appears when ETF is reconstituted from its guanidine-denatured subunits and FAD. A similar anomalous spectrum was observed for AMP-free pig ETF under acidic conditions, suggesting a common flavin environment between pig and M. elsdenii ETFs. (+info)
Propionispora hippei sp. nov., a novel Gram-negative, spore-forming anaerobe that produces propionic acid.
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A Gram-negative, spore-forming anaerobe, KS(T), was isolated from an enrichment culture that was set up for anaerobic degradation of the aliphatic polyester poly(propylene adipate). The strain had the cellular organization of Sporomusa, vibrio-shaped cells and terminal round spores, and fermented sugars and sugar alcohols to propionic and acetic acid. Based on the morphological and physiological features as well as on a 16S rRNA gene similarity of 98 %, it was grouped with Propionispora vibrioides. A relatively low DNA-DNA hybridization value with the type strain of this species (47 %), and differences in substrate utilization and spore morphology, suggested that the strain should be classified in a separate species, Propionispora hippei sp. nov., with KS(T) as the type strain (=DSM 15287(T)=ATCC BAA-665(T)). (+info)
Thermosinus carboxydivorans gen. nov., sp. nov., a new anaerobic, thermophilic, carbon-monoxide-oxidizing, hydrogenogenic bacterium from a hot pool of Yellowstone National Park.
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A new anaerobic, thermophilic, facultatively carboxydotrophic bacterium, strain Nor1(T), was isolated from a hot spring at Norris Basin, Yellowstone National Park. Cells of strain Nor1(T) were curved motile rods with a length of 2.6-3 microm, a width of about 0.5 microm and lateral flagellation. The cell wall structure was of the Gram-negative type. Strain Nor1(T) was thermophilic (temperature range for growth was 40-68 degrees C, with an optimum at 60 degrees C) and neutrophilic (pH range for growth was 6.5-7.6, with an optimum at 6.8-7.0). It grew chemolithotrophically on CO (generation time, 1.15 h), producing equimolar quantities of H(2) and CO(2) according to the equation CO+H(2)O-->CO(2)+H(2). During growth on CO in the presence of ferric citrate or amorphous ferric iron oxide, strain Nor1(T) reduced ferric iron but produced H(2) and CO(2) at a ratio close to 1 : 1, and growth stimulation was slight. Growth on CO in the presence of sodium selenite was accompanied by precipitation of elemental selenium. Elemental sulfur, thiosulfate, sulfate and nitrate did not stimulate growth of strain Nor1(T) on CO and none of these chemicals was reduced. Strain Nor1(T) was able to grow on glucose, sucrose, lactose, arabinose, maltose, fructose, xylose and pyruvate, but not on cellobiose, galactose, peptone, yeast extract, lactate, acetate, formate, ethanol, methanol or sodium citrate. During glucose fermentation, acetate, H(2) and CO(2) were produced. Thiosulfate was found to enhance the growth rate and cell yield of strain Nor1(T) when it was grown on glucose, sucrose or lactose; in this case, acetate, H(2)S and CO(2) were produced. In the presence of thiosulfate or ferric iron, strain Nor1(T) was also able to grow on yeast extract. Lactate, acetate, formate and H(2) were not utilized either in the absence or in the presence of ferric iron, thiosulfate, sulfate, sulfite, elemental sulfur or nitrate. Growth was completely inhibited by penicillin, ampicillin, streptomycin, kanamycin and neomycin. The DNA G+C content of the strain was 51.7+/-1 mol%. Analysis of the 16S rRNA gene sequence revealed that strain Nor1(T) belongs to the Bacillus-Clostridium phylum of the Gram-positive bacteria. On the basis of the studied phenotypic and phylogenetic features, we propose that strain Nor1(T) be assigned to a new genus, Thermosinus gen. nov. The type species is Thermosinus carboxydivorans sp. nov. (type strain, Nor1(T)=DSM 14886(T)=VKM B-2281(T)). (+info)
The hydrogen-tritium exchange activity of Megasphaera elsdenii hydrogenase.
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The hydrogenase of Megasphaera elsdenii was purified to a specific activity of 350 units/mg. The hydrogen-tritium exchange assay of Hallahan et al. [Hallahan, D.L., Fernandez, V. M., Hatchikian, E. C. and Hall, D. O. (1986) Biochimie (Paris) 68, 49-54] was adapted to allow its use in the study of the M. elsdenii hydrogenase preparation. Under the assay conditions routinely employed, the enzyme's exchange activity was inhibited by Tris/HCl and MgCl2; it was stimulated by ethylene glycol. Maximal activity in this standard assay occurred at pH 7.1. The effect of the concentration of molecular hydrogen (1H2 plus 3H1H) on the exchange activity was studied. The resulting double-reciprocal plot was linear; its slope and its intercepts on the ordinate and abscissa were pH-dependent. The rate equations for a number of models of the exchange activity were derived. Each model gave rise to a linear double-reciprocal plot at constant pH, but none could explain fully the observed effects of varying pH. The experimental data corresponded most closely to the predictions of models in which protons were treated both as substrates and as regulators of the enzyme's activity. (+info)