No abstract

Enterococcus sp. K-4, with a bacteriocin-like activity against E. faecium, was isolated from grass silage in Thailand. Morphological, physiological, and phylogenetic studies clearly identified strain K-4 as a strain of E. faecalis. Strain K-4 produced a maximal amount of bacteriocin at 43-45 degrees C. We purified, for the first time, the bacteriocin produced at high temperature by E. faecalis to homogeneity, using adsorption on cells of the producer strain and reversed-phase liquid chromatography. The bacteriocin, designated enterocin SE-K4, is a peptide of about 5 kDa as measured by SDS-PAGE, and Mass spectrometry analysis found the molecular mass of 5356.2, which is in good agreement. The amino acid sequencing of the N-terminal end of enterocin SE-K4 showed apparent sequence similarity to class IIa bacteriocins. Enterocin SE-K4 was active against E. faecium, E. faecalis, Bacillus subtilis, Clostridium beijerinckii, and Listeria monocytogenes. Enterocin SE-K4 is very heat stable.

A combined use of molecular ecological techniques and geochemical surveys revealed that thermophilic or hyperthermophilic microorganisms living in geothermal environments are likely to be implicated in the formation of biogenic siliceous deposits. Electron microscopic observations indicated that numerous microorganism-like fabrics were preserved in naturally occurring siliceous deposits such as siliceous sinter, geyserite, and silica scale, which suggests microbial contribution to silica precipitation. Molecular phylogenetic analyses suggested that extreme thermophilic bacteria within the genera Thermus and Hydrogenobacter are predominant components among the indigenous microbial community in siliceous deposits formed in pipes and equipment of Japanese geothermal power plants. These bacteria seem to actively contribute to the rapid formation of huge siliceous deposits. Additionally, in vitro examination suggested that Thermus cells induced the precipitation of supersaturated amorphous silica during the exponential growth phase, concomitant with the production of a specific cell envelope protein. Dissolved silica in geothermal hot water may be a significant component in the maintenance of position and survival of microorganisms in limited niches.

A Gram-positive, coccus-shaped, lactic acid bacterium, strain NGRI 0510Q T , was isolated from ryegrass silage produced in Okinawa Prefecture, Japan. The cell is non-spore-forming, nonmotile, and occurs in pairs or tetrads. The strain is homofermentative and produces D-and L-lactic acid from glucose. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain NGRI 0510Q T belongs to the genus Pediococcus and clusters within the Pediococcus acidilactici and Pediococcus pentosaceus group, with 98.2 and 96.9 % sequence identity, respectively. DNA-DNA relatedness between strain NGRI 0510Q T and P. acidilactici JCM 8797 T and P. pentosaceus JCM 5890 T was 19.3 and 17.3 %, respectively. Based on its phenotypic characteristics, phylogenetic relationship and DNA-DNA relatedness, NGRI 0510Q T (5JCM 15055 T 5DSM 19927 T ) represents the type strain of a novel species, for which the name Pediococcus lolii sp. nov. is proposed.

At Steep Cone hot spring, Lower Geyser Basin, Yellowstone National Park, a mound of siliceous deposits called "siliceous sinter" forms from discharged boiling geothermal water that is supersaturated with amorphous silica. Electron-probe microanalyzer (EPMA) observations suggested that silica is deposited on the surface of the cells and that microorganisms affect the formation of the siliceous sinter. EPMA signals and backscattered electron images of sinter samples taken at the inner wall of the boiling pool revealed framboidal pyrite structures associated with a network of silicified microbial structures. The structure of bacterial community in a beigecolored sinter sediment (75.8°C, pH 8.6) was studied by molecular clone type phylogenetic analysis of PCR-mediated 16S rDNA fragments. The bacterial rDNA clones found indicated the presence of a complex community in the sinter sediment. Sequences closely related to the genera Thermus and Saccharomonospora were dominated; evidence of indigenous microbial components.