Desulfovibrio idahonensis sp. nov., sulfate-reducing bacteria isolated from a metal(loid)-contaminated freshwater sediment.

Two novel sulfate-reducing bacteria, strains CY1T and CY2, were isolated from heavy-metal-contaminated sediments of Lake Coeur d'Alene, Idaho, USA. Strains CY1T and CY2 were found to contain c-type cytochromes and to reduce sulfate, sulfite, thiosulfate, elemental sulfur, DMSO, anthraquinone disulfonate and fumarate using lactate as an electron donor. In a comparison of 16S rRNA gene sequences, CY1T and CY2 were found to be 100% identical, but only 97 and 92.4% similar, respectively, to the type strains of Desulfovibrio mexicanus and Desulfovibrio aminophilus. Unlike these species, however, CY1T was neither able to disproportionate thiosulfate nor able to use yeast extract or amino acids as electron donors. These data, considered in conjunction with differences among strain CY1T and the two related type strains in chemotaxonomy, riboprint patterns, temperature and pH optima, support recognition of a distinct and novel species within the genus Desulfovibrio, Desulfovibrio idahonensis sp. nov., with the type strain CY1T (=DSM 15450T=JCM 14124T).

Desulfosporosinus lacus sp. nov., a sulfate-reducing bacterium isolated from pristine freshwater lake sediments.

A novel sulfate-reducing bacterium was isolated from pristine sediments of Lake Stechlin, Germany. This strain, STP12(T), was found to contain predominantly c-type cytochromes and to reduce sulfate, sulfite and thiosulfate using lactate as an electron donor. Although STP12(T) could not utilize elemental sulfur as an electron acceptor, it could support growth by dissimilatory Fe(III) reduction. In a comparison of 16S rRNA gene sequences, STP12(T) was 96.7 % similar to Desulfosporosinus auripigmenti DSM 13351(T), 96.5 % similar to Desulfosporosinus meridiei DSM 13257(T) and 96.4 % similar to Desulfosporosinus orientis DSM 765(T). DNA-DNA hybridization experiments revealed that strain STP12(T) shows only 32 % reassociation with the type strain of the type species of the genus, D. orientis DSM 765(T). These data, considered in conjunction with strain-specific differences in heavy metal tolerance, cell-wall chemotaxonomy and riboprint patterns, support recognition of strain STP12(T) (=DSM 15449(T)=JCM 12239(T)) as the type strain of a distinct and novel species within the genus Desulfosporosinus, Desulfosporosinus lacus sp. nov.

Molecular analysis of microbial community structure in an arsenite-oxidizing acidic thermal spring.

Electron microscopy (EM), denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequencing were used to examine the structure and diversity of microbial mats present in an acid-sulphate-chloride (pH 3.1) thermal (58-62 degrees C) spring in Norris Basin, Yellowstone National Park, WY, USA, exhibiting rapid rates of arsenite oxidation. Initial visual assessments, scanning EM and geochemical measurements revealed the presence of three distinct mat types. Analysis of 16S rDNA fragments with DGGE confirmed the presence of different bacterial and archaeal communities within these zones. Changes in the microbial community appeared to coincide with arsenite oxidation activity. Phylogenetic analysis of 1400 bp 16S rDNA sequences revealed that clone libraries prepared from both arsenic redox active and inactive bacterial communities were dominated by sequences phylogenetically related to Hydrogenobacter acidophilus and Desulphurella sp. The appearance of archaeal 16S rDNA sequences coincided with the start of arsenite oxidation, and sequences were obtained showing affiliation with both Crenarchaeota and Euryarchaeota. The majority of archaeal sequences were most similar to sequences obtained from marine hydrothermal vents and other acidic hot springs, although the level of similarity was typically just 90%. Arsenite oxidation in this system may result from the activities of these unknown archaeal taxa and/or the previously unreported arsenic redox activity of H. acidophilus- or Desulphurella-like organisms. If the latter, arsenite oxidation must be inhibited in the initial high-sulphide zone of the spring, where no change in the distribution of arsenite versus arsenate was observed.

Rapid oxidation of arsenite in a hot spring ecosystem, Yellowstone National Park.

Geothermal springs within Yellowstone National Park (YNP) often contain arsenic (As) at concentrations of 10-40 microM, levels that are considered toxic to many organisms. Arsenite (As(III)) is often the predominant valence state at the point of discharge but is rapidly oxidized to arsenate (As(V)) during transport in shallow surface water. The current study was designed to establish rates and possible mechanisms of As(III) oxidation and to characterize the geochemical environment associated with predominant microbial mats in a representative acid-sulfate-chloride (pH 3.1) thermal (58-62 degrees C) spring in Norris Basin, YNP. At the spring origin, total soluble As was predominantly As(III) at concentrations of 33 microM. No oxidation of As(III) was detected over the first 2.7 m downstream from the spring source, corresponding to an area dominated by a yellow filamentous S0-rich microbial mat However, rapid oxidation of As(III) to As(V) was observed between 2.7 and 5.6 m, corresponding to termination of the S0-rich mats, decreases in dissolved sulfide, and commencement of a brown Fe/As-rich mat. Rates of As(II) oxidation were estimated, yielding an apparent first-order rate constant of 1.2 min(-1) (half-life = 0.58 min). The oxidation of As(III) was shown to require live organisms present just prior to and within the Fe/As-rich mat. Complementary analytical tools used to characterize the brown mat revealed an As:Fe molar ratio of 0.7 and suggested that this filamentous microbial mat contains iron(III) oxyhydroxide coprecipitated with As(V). Results from the current work are the first to provide a comprehensive characterization of microbially mediated As(III) oxidation and the geochemical environments associated with microbial mats in acid-sulfate-chloride springs of YNP.

[Problems in obtaining antiserum to staphylococcal enterotoxin D]. / Problemi pri poluchavaneto na stafilokokov enterotoksin-D--antiserum

Experimentally were demonstrated the difficulties overcome and the possibilities of producing a Staphylococcus-enterotoxin D antiserum of a 1:80 titer. The product was shown to be suitable for work as well as for further studies. Given are the schemes of immunizing a rabbit serving as a serum producer and those for purifying the antiserum (eliminating heterologous antibodies), its titration with a microimmunodiffusion test, etc. In this connection some problems are referred to concerning the production of the amounts necessary of enterotoxin D, its purification and toxicity for test animals, etc., that are successfully solved by the authors.