Thermovorax subterraneus, gen. nov., sp. nov., a thermophilic hydrogen-producing bacterium isolated from geothermally active underground mine

Abstract

A thermophilic, rod-shaped, motile, Gram-positive, spore-forming bacterium strain 70B(T) was isolated from a geothermally active underground mine in Japan. The temperature and pH range for growth was 50-81 degrees C (optimum 71 degrees C) and 6.2-9.8 (optimum pH 7-7.5), respectively. Growth occurred in the presence 0-2% NaCl (optimum 1% NaCl). Strain 70B(T) could utilize glucose, fructose, mannose, mannitol, pyruvate, cellobiose and tryptone as substrates. Thiosulfate was used as electron acceptor. Major whole-cell fatty acids were iso-C(15:0), C(16:0) DMA (dimethyl acetal), C(16:0) and anteiso-C(15:0). The G+C mol% of the DNA was 44.2%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the closest relatives of strain 70B(T) were Thermosediminibacter oceani DSM 16646(T) (94% similarity) and Thermosediminibacter litoriperuensis DSM 16647 (93% similarity). The phenotypic, chemotaxonomic and phylogenetic properties suggest that strain 70B(T) represents a novel species in a new genus, for which the name Thermovorax subterraneus gen. nov., sp. nov. is proposed. The type strain of Thermovorax subterraneus is 70B(T) (=DSM 21563 = JCM 15541).

Draft genome sequence of Thermovorax subterraneus 70BT, a thermophile isolated from a geothermally active underground mine that produces hydrogen

“…Thermovorax subterraneus 70B T (= DSM 21563 T = JCM 15541 T ) was isolated from a geothermally active underground mine located in Japan [1] . Strain 70B T is a Gram-positive, rod-shaped, and motile thermophile that grows optimally at 71°C with pH 7.0–7.5.…”

“…A heat treatment analysis at 95°C for 25 minutes does not destroy the strain, indicating that it is heat stable. An earlier study had examined strain 70B T phenotypically, chemotaxonomically, and phylogenetically (16S rRNA gene) against close strains from other genera [1] . As of now, strain 70B T is classified under the class Clostridia , the order Thermosediminibacterales , and the family Thermosediminibacteraceae .…”

“…According to the research group that isolated strain 70B T earlier, the bacterium was able to produce hydrogen gas [1] . Compared to mesophilic bacteria, thermophilic bacteria generate a higher yield of biohydrogen in dark fermentation [7] .…”

Thermophilic biohydrogen production: how far are we?

“…Recent reviews list many of those microorganisms involved (Kengen et al 2009; van Niel et al 2011), so here, only a selection of the best performers is given (Tables 1 and 2). Most of these organisms were isolated from extremely hot and reducing conditions (Fiala and Stetter 1986; Huber et al 1986; Rainey et al 1994; Xue et al 2001; Mäkinen et al 2009), under which they produce reduced metabolic end products, including H 2 , as an electron sink for reducing equivalents (Thauer et al 1977). …”

Comparison of mesophilic and thermophilic anaerobic hydrogen production by hot spring enrichment culture

“…Koskinen et al (2008) studied hot spring enrichments for hydrogen production in the temperature range of 37 Ce70 C and reported 45 C was optimal for H 2 production (1.67 mol H 2 /mol glucose) [7]. Mä kinen et al (2009) studied hydrogen production by a thermophilic strain, Thermovorax subterraneus, isolated from a geothermally active underground mine and reported that optimum temperature was 71 C [8].…”