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     

Clostridium alkalicellum sp. nov., an Obligately Alkaliphilic Cellulolytic Bacterium from a Soda Lake in the Baikal Region

Microbiology - The first anaerobic alkaliphilic cellulolytic microorganism has been isolated from the Verkhnee Beloe soda lake (Buryatiya, Russia) with pH 10.2 and a salt content of up to 24 g/l....     

“Candidatus Contubernalis alkalaceticum,” an Obligately Syntrophic Alkaliphilic Bacterium Capable of Anaerobic Acetate Oxidation in a Coculture with Desulfonatronum cooperativum

From the silty sediments of the Khadyn soda lake (Tuva), a binary sulfidogenic bacterial association capable of syntrophic acetate oxidation at pH 10.0 was isolated. An obligately syntrophic, gram-positive, spore-forming alkaliphilic rod-shaped bacterium performs acetate oxidation in a syntrophic association with a hydrogenotrophic, alkaliphilic sulfate-reducing bacterium; the latter organism was previously isolated and characterized as the new species Desulfonatronum cooperativum. Other sulfate-reducing bacteria of the genera Desulfonatronum and Desulfonatronovibrio can also act as the hydrogenotrophic partner. Apart from acetate, the syntrophic culture can oxidize ethanol, propanol, isopropanol, serine, fructose, and isobutyric acid. Selective amplification of 16S rRNA gene fragments of the acetate-utilizing syntrophic component of the binary culture was performed; it was found to cluster with clones of uncultured gram-positive bacteria within the family Syntrophomonadaceae. The acetate-oxidizing bacterium is thus the first representative of this cluster obtained in a laboratory culture. Based on its phylogenetic position, the new acetate-oxidizing syntrophic bacterium is proposed in the Candidatus status for a new genus and species: “Candidatus Contubernalis alkalaceticum.”     

Equilibrium between the "genuine mutualists" and "symbiotic cheaters" in the bacterial population co-evolving with plants in a facultative symbiosis

The mathematical model for evolution of the plant-microbe facultative mutualistic interactions based on the partners’ symbiotic feedbacks is constructed. Using the example of rhizobia-legume symbiosis, we addressed these feedbacks in terms of the metabolic exchange resulting in the parallel improvements of the partners’ fitness (positive feedbacks). These improvements are correlated to the symbiotic efficiency dependent on the ratio of N₂-fixing bacterial strains (“genuine mutualists”) to the non- N₂-fixing strains (“symbiotic cheaters”) in the root nodules. The computer experiments demonstrated that an interplay between the frequency-dependent selection (FDS) and the Darwinian (frequency-independent) selection pressures implemented in the partners’ populations ensures an anchoring or even domination for the newly generated host-specific mutualists (which form N₂-fixing nodules only with one of two available plant genotypes) more successfully than for the non-host-specific mutualists (which form N₂-fixing nodules with both plant genotypes). The created model allows us to consider the mutualistic symbiosis as a finely balanced polymorphic system wherein the equilibrium in bacterial population may be shifted in favor of “genuine mutualists” due to the partner-stipulated selection for an improved symbiotic efficiency implemented in the plant population.     

Hydrogenosomes: convergent adaptations of mitochondria to anaerobic environments

Hydrogenosomes are membrane-bound organelles that compartmentalise the final steps of energy metabolism in a number of anaerobic eukaryotes. They produce hydrogen and ATP. Here we will review the data, which are relevant for the questions: how did the hydrogenosomes originate, and what was their ancestor? Notably, there is strong evidence that hydrogenosomes evolved several times as adaptations to anaerobic environments. Most likely, hydrogenosomes and mitochondria share a common ancestor, but an unequivocal proof for this hypothesis is difficult because hydrogenosomes lack an organelle genome - with one remarkable exception (Nyctotherus ovalis). In particular, the diversity of extant hydrogenosomes hampers a straightforward analysis of their origins. Nevertheless, it is conceivable to postulate that the common ancestor of mitochondria and hydrogenosomes was a facultative anaerobic organelle that participated in the early radiation of unicellular eukaryotes. Consequently, it is reasonable to assume that both, hydrogenosomes and mitochondria are evolutionary adaptations to anaerobic or aerobic environments, respectively.     

Barring gene expression after XIST: maintaining facultative heterochromatin on the inactive X

X chromosome inactivation refers to the developmentally regulated process of silencing gene expression from all but one X chromosome per cell in female mammals in order to equalize the levels of X chromosome derived gene expression between the sexes. While much attention has focused on the genetic and epigenetic events early in development that initiate the inactivation process, it is also important to understand the events that ensure maintenance of the inactive state through subsequent cell divisions. Gene silencing at the inactive X chromosome is irreversible in somatic cells and is achieved through the formation of facultative heterochromatin (visible as the Barr body) that is remarkably stable and faithfully preserved. Here we review the many features of inactive X chromatin in terminally differentiated cells and address the highly redundant mechanisms of maintaining the inactive X chromatin.     

Effect of subtherapeutic concentrations of tylosin on the inhibitory stringency of a mixed anaerobe continuous-flow culture of chicken microflora against Escherichia coli O157:H7

AIMS: The aim of this study was twofold: first to determine the effect of subtherapeutic concentrations of tylosin, a macrolide antibiotic used for growth promotion, on a mixed anaerobic continuous-flow fermentation culture of chicken gastrointestinal microorganisms (CCF) and secondly, to determine if these concentrations would allow persistence of Escherichia coli O157:H7 in CCF. METHODS AND RESULTS: CCF was treated with tylosin at 10.0, 20.0 and 40.0 microg ml(-1). Tylosin treatment resulted in a significant (P < 0.0001) decrease in total volatile fatty acids (VFAs) from a mean concentration of 101 +/- 10.8 micromol ml(-1) in control cultures to 32.0 +/- 6.3 and 40.2 +/- 9.6 micromol ml(-1) in 10 and 40 microg ml(-1) treated cultures, respectively. Untreated CCF challenged with E. coli O157:H7 cleared the challenge microorganism in 7 days at a rate of 0.96 log10 CFU ml(-1) day(-1). In contrast, E. coli O157:H7 persisted in all tylosin treated cultures. CONCLUSIONS: In the presence of tylosin, E. coli O157:H7 was able to persist in the CCF culture. The significant decrease in the production of VFAs may have been a contributing factor. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of low-level, growth-promoting antimicrobials may compromise the ability of normal microflora that serve as a natural host defence against infection.     

Classification and typing methods of black-pigmented Gram-negative anaerobes

Abstract Until recently, black-pigmented Gram-negative anaerobes were classified as ‘black-pigmented Bacteroides ’. At present, 11 distinct species are recognized in this group. Because of major differences with Bacteroides fragilis , the type species of the genus Bacteroides , new genera have been proposed: Porphyromonas for three asaccharolytic species, and Prevotella for the saccharolytic species. Typing methods have been developed for some species of black-pigmented Gram-negative anaerobes. These include biotyping and serotyping, but relatively few types can be distinguished with these methods. Recently, DNA restriction endonuclease analysis has been used for typing of P. gingivalis, Pr. intermedia and P. endodontalis strains. Great heterogeneity was observed within all three species. This typing method can be useful for epidemiological studies.     

用斜面法分离厌氧微生物

描述了一种在斜面上分离厌氧微生物的方法,包括培养基、稀释细菌悬浮液的点样和菌落的挑取等。用此法长出的菌落形态清晰可见,便于分离。此法简便、易行,亦可用于观察厌氧菌的斜面培养特征和菌种保藏。     

Geoalkalibacter ferrihydriticus gen. nov. sp. nov., the first alkaliphilic representative of the family Geobacteraceae, isolated from a soda lake

Investigation of iron reduction in bottom sediments of alkaline soda lakes resulted in the isolation of a new obligately anaerobic iron-reducing bacterium, strain Z-0531, from Lake Khadyn (Tuva, Russia) sediment samples. The cells of strain Z-0531 are short (1.0–1.5 by 0.3–0.5 μm), motile, non-spore-forming, gram-negative rods. The isolate is an obligate alkaliphile, developing in the pH range of 7.8–10.0, with an optimum at pH 8.6. It does not require NaCl but grows at NaCl concentrations of 0–50 g/l. It can oxidize acetate with such electron acceptors as amorphous Fe(III) hydroxide (AFH), EDTA-Fe(III), anthraquinone-2,6-disulfonate (quinone), Mn(IV), and S⁰. On medium with EDTA-Fe(III), the isolate can oxidize, apart from acetate, ethanol, pyruvate, oxalate, arginine, tartrate, lactate, propionate, and serine. H₂ is not utilized. The reduced products formed during growth with AFH are siderite or magnetite, depending on the growth conditions. The isolate is incapable of fermenting sugars, peptides, and amino acids. Yeast extract or vitamins are required as growth factors. The organism is capable of dinitrogen fixation and harbors the nifH gene. The DNA G+C content is 55.3 mol %. 16S rRNA analysis places strain Z-0531 into the family Geobacteraceae. Its closest relative (93% similarity) is Desulfuromonas palmitatis. Based on phenotypic distinctions and phylogenetic position, it is proposed that this strain be assigned to the new genus and species Geoalkalibacter ferrihydriticus gen. nov., sp. nov. (Z-0531^T-DSMZ-17813-VKMB-2401). Original Russian Text ? D.G. Zavarzina, T.V. Kolganova, E.S. Boulygina, N.A. Kostrikina, T.P. Tourova, G.A. Zavarzin, 2006, published in Mikrobiologiya, 2006, Vol. 75, No. 6, pp. 775–785.