Diversity and distribution of thermophilic hydrogenogenic carboxydotrophs revealed by microbial community analysis in sediments from multiple hydrothermal environments in Japan.

In hydrothermal environments, carbon monoxide (CO) utilisation by thermophilic hydrogenogenic carboxydotrophs may play an important role in microbial ecology by reducing toxic levels of CO and providing H2 for fuelling microbial communities. We evaluated thermophilic hydrogenogenic carboxydotrophs by microbial community analysis. First, we analysed the correlation between carbon monoxide dehydrogenase (CODH)-energy-converting hydrogenase (ECH) gene cluster and taxonomic affiliation by surveying an increasing genomic database. We identified 71 genome-encoded CODH-ECH gene clusters, including 46 whose owners were not reported as hydrogenogenic carboxydotrophs. We identified 13 phylotypes showing > 98.7% identity with these taxa as potential hydrogenogenic carboxydotrophs in hot springs. Of these, Firmicutes phylotypes such as Parageobacillus, Carboxydocella, Caldanaerobacter, and Carboxydothermus were found in different environmental conditions and distinct microbial communities. The relative abundance of the potential thermophilic hydrogenogenic carboxydotrophs was low. Most of them did not show any symbiotic networks with other microbes, implying that their metabolic activities might be low.

Nocapyrones: α- and γ-pyrones from a marine-derived Nocardiopsis sp.

One new α-pyrone (nocapyrone R (1)), and three known γ-pyrones (nocapyrones B, H and L (2-4)) were isolated from the culture extract of a Nocardiopsis strain collected from marine sediment. Structures of these compounds were determined on the basis of spectroscopic data including NMR and MS. γ-Pyrones 2-4 were found to induce adiponectin production in murine ST-13 preadipocyte cells but the α-pyrone 1 had no activity. The absolute configuration of the anteiso-methyl branching in 4 was determined by HPLC comparison of a degraded product of 4 with standard samples as a 2:3 enantiomeric mixture of (R)- and (S)-isomers.

A thermophilic, hydrogenogenic and carboxydotrophic bacterium, Calderihabitans maritimus gen. nov., sp. nov., from a marine sediment core of an undersea caldera.

A hydrogenogenic, carboxydotrophic marine bacterium, strain KKC1(T), was isolated from a sediment core sample taken from a submerged marine caldera. Cells were non-motile, Gram-stain-negative, 1.0-3.0 µm straight rods, often observed with round endospores. Strain KKC1(T) grew at 55-68 °C, pH 5.2-9.2 and 0.8-14 % (w/v) salinity. Optimum growth occurred at 65 °C, pH 7.0-7.5 and 2.46 % salinity with a doubling time of 3.7 h. The isolate grew chemolithotrophically, producing H2 from carbon monoxide (CO) oxidation with reduction of various electron acceptors, e.g. sulfite, thiosulfate, fumarate, ferric iron and AQDS (9,10-anthraquinone 2,6-disulfonate). KKC1(T) grew heterotrophically on pyruvate, lactate, fumarate, glucose, fructose and mannose with thiosulfate as an electron acceptor. When grown mixotrophically on CO and pyruvate, C16 : 0 constituted almost half of the total cellular fatty acids. The DNA G+C content was 50.6 mol%. The 16S rRNA gene sequence of KKC1(T) was most closely related to those of members of the genus Moorella with similarity ranging from 91 to 89 %. Based on physiological and phylogenetic novelty, we propose the isolate as a representative of a new genus and novel species with the name Calderihabitans maritimus gen. nov., sp. nov.; the type strain of the type species is KKC1(T) ( = DSM 26464(T) = NBRC 109353(T)).

Isolation of a bacterium possessing a haloacid dehalogenase from a marine sediment core.

A monobromoacetic acid-resistant bacterium, Bacillus strain I37c, was isolated from a marine sediment core. The strain grew in a medium containing 1.8 mg mL(-1) of monobromoacetic acid. It produced constitutively a 2-haloacid dehalogenase that catalyzed the dehalogenation of monobromoacetic acid, monochloroacetic acid, and both L- and D-2-chloropropionic acid. The optimal pH and temperature for the activity measured using a partly purified enzyme were similar to those of known group I haloacid dehalogenases.

Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov., moderately halophilic bacteria isolated from a deep-sea methane cold seep.

Two Gram-positive, rod-shaped, moderately halophilic bacteria were isolated from a deep-sea carbonate rock at a methane cold seep in Kuroshima Knoll, Japan. These bacteria, strains IS-Hb4(T) and IS-Hb7(T), were spore-forming and non-motile. They were able to grow at temperatures as low as 9 degrees C and hydrostatic pressures up to 30 MPa. Based on high sequence similarity of their 16S rRNA genes to those of type strains of the genus Halobacillus, from 96.4 % (strain IS-Hb7(T) to Halobacillus halophilus NCIMB 9251(T)) to 99.4 % (strain IS-Hb4(T) to Halobacillus dabanensis D-8(T)), the strains were shown to belong to this genus. DNA-DNA relatedness values of 49.5 % and 1.0-33.0 %, respectively, were determined between strains IS-Hb4(T) and IS-Hb7(T) and between these strains and other Halobacillus type strains. Both strains showed the major menaquinone MK7 and L-orn-D-Asp cell-wall peptidoglycan type. Straight-chain C(16 : 0), unsaturated C(16 : 1)omega7c alcohol and C(18 : 1)omega7c and cyclopropane C(19 : 0) cyc fatty acids were predominant in both strains. The DNA G+C contents of IS-Hb4(T) and IS-Hb7(T) were respectively 43.3 and 42.1 mol%. Physiological and biochemical analyses combined with DNA-DNA hybridization results allowed us to place strains IS-Hb4(T) (=JCM 14154(T)=DSM 18394(T)) and IS-Hb7(T) (=JCM 14155(T)=DSM 18393(T)) in the genus Halobacillus as the respective type strains of the novel species Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov.