Tomonori Takashina

Aciditerrimonas ferrireducens gen. nov., sp. nov., an iron-reducing thermoacidophilic actinobacterium isolated from a solfataric field.

An iron-reducing, moderately thermophilic, acidophilic actinobacterium, strain IC-180(T), isolated from a solfataric field in Hakone, Japan, was subjected to polyphasic taxonomic analysis. Strain IC-180(T) was a motile, short rod-shaped, Gram-positive bacterium that was able to grow at temperatures of 35-58 °C (optimally at 50 °C) and at pH 2.0-4.5 (optimally at pH 3.0). The strain grew aerobically and heterotrophically. It also grew anaerobically or autotrophically by dissimilatory reduction of ferric iron. No oxidation of ferrous iron was observed. Major cellular fatty acids detected were iso-C(16 : 0), anteiso-C(17 : 0) and iso-C(18 : 0); the major menaquinone was MK-9(H(8)). Phosphatidyl-N-methylethanolamine and an unknown ninhydrin-positive phosphoglycolipid were detected. The total DNA G+C content was 74.1 mol%. 16S rRNA gene sequence comparisons revealed that strain IC-180(T) was a member of the order Acidimicrobiales and clustered coherently with uncultured actinobacteria from a geothermal site and a bioreactor operated under moderately thermophilic conditions. This cluster could be distinguished from the two other clusters comprising the families of this order, Acidimicrobiaceae and Iamiaceae, respectively. Based on the properties of strain IC-180(T) determined in this polyphasic taxonomic study, this strain represents a novel species in a new genus in the order Acidimicrobiales, for which the name Aciditerrimonas ferrireducens gen. nov., sp. nov. is proposed; the type strain is IC-180(T) ( = JCM 15389(T)  = DSM 45281(T)).

Identification of carotenoids from the extremely halophilic archaeon Haloarcula japonica

The carotenoids produced by extremely halophilic archaeon Haloarcula japonica were extracted and identified by their chemical, chromatographic, and spectroscopic characteristics (UV-Vis and mass spectrometry). The composition (mol%) was 68.1% bacterioruberin, 22.5% monoanhydrobacterioruberin, 9.3% bisanhydrobacterioruberin, <0.1% isopentenyldehydrorhodopin, and trace amounts of lycopene and phytoene. The in vitro scavenging capacity of a carotenoid, bacterioruberin, extracted from Haloarcula japonica cells against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals was evaluated. The antioxidant capacity of bacterioruberin was much higher than that of β -carotene.

Athalassotoga saccharophila gen. nov., sp. nov., isolated from an acidic terrestrial hot spring, and proposal of Mesoaciditogales ord. nov. and Mesoaciditogaceae fam. nov. in the phylum Thermotogae

A novel moderately thermophilic, weakly acidophilic, heterotrophic, anaerobic, short-rod bacterium having an outer sheath-like structure (toga) was isolated from a low-salt acidic terrestrial hot spring in Oku-Shiobara, Tochigi, Japan. The strain, designated NAS-01T, grew between 30 and 60 °C (optimum 55 °C), and at pH 4.5 and 7.5 (optimum pH 5.5 to 6.0) and could not grow in media with ≥ 1 % NaCl (optimum 0 % NaCl). It utilized Fe(III), thiosulfate or l-cystine as electron acceptor for growth, and yeast extract, peptone or a variety of sugars as carbon and energy sources. The major cellular fatty acid was C16 : 0, and no lipoquinone was detected. Strain NAS-01T contained phospholipids and glycolipids, but not aminolipids. The DNA G+C content was 41.1 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the strain was included in the phylum Thermotogae, and was closely related to Mesoaciditoga lauensis. The 16S rRNA gene sequence similarity between them was 90 %, and they were deeply branched off the rest of the known Thermotogae species. On the basis of the phylogenetic and ecophysiological properties, strain NAS-01T represents a novel species of a new genus in the phylum Thermotogae, for which we propose the name Athalassotoga saccharophila gen. nov., sp. nov. The type strain of the type species is NAS-01T ( = JCM 19762T = DSM 28954T). In addition, we propose a new order and family, Mesoaciditogales ord. nov. and Mesoaciditogaceae fam. nov., respectively, to accommodate the novel genus and the closely related genus Mesoaciditoga.

Bioethanol production from steam-exploded rice husk by recombinant Escherichia coli KO11

Rice husk is one of the most abundant types of lignocellulosic biomass. Because of its significant amount of sugars, such as cellulose and hemicellulose, it can be used for the production of biofuels such as bioethanol. However, the complex structure of lignocellulosic biomass, consisting of cellulose, hemicellulose and lignin, is resistant to degradation, which limits biomass utilization for ethanol production. The protection of cellulose by lignin contributes to the recalcitrance of lignocelluloses to hydrolysis. Therefore, we conducted steam-explosion treatment as pretreatment of rice husk. However, recombinant Escherichia coli KO11 did not ferment the reducing sugar solution obtained by enzymatic saccharification of steam-exploded rice husk. When the steam-exploded rice husk was washed with hot water to remove inhibitory substances and M9 medium (without glucose) was used as a fermentation medium, E. coli KO11 completely fermented the reducing sugar solution obtained by enzymatic saccharification of hot water washing-treated steam-exploded rice husk to ethanol. We report here the efficient production of bioethanol using steam-exploded rice husk.

Diversity of thermophilic archaeal isolates from hot springs in Japan

In the light of the significance of extremophiles as model organisms to access possible extraterrestiral life, we provide a short review of the systematics of thermophilic Archaea, and introduce our exploratory research of novel thermophilic Archaea from hot springs in Japan. Up to date, we have isolated 162 strains of the thermophilic Archaea from hot springs in Japan by the enrichment method or the most probable number/PCR method, and the 16S rRNA gene sequences were determined to reveal their phylogenetic diversity. The sequence comparison illustrated that the isolates belonged to the orders Sulfolobales (117 isolates) , Thermoproteales (29 isolates), Desulfurococcales (8 isolates) and Thermoplasmatales (8 isolates), and there were six separate lineages representing new genera, and at least seven new species as predicted by the phylogenetic distance to known species. The collection of isolates not only included novel taxa but would give some implication for a necessity to reevaluate the current taxonomy of the thermophilic Archaea.