Oceanithermus desulfurans sp. nov., a novel thermophilic, sulfur-reducing bacterium isolated from a sulfide chimney in Suiyo Seamount

Abstract

A novel thermophilic, microaerophilic, sulfur-reducing bacterium designated strain St55BT was isolated from a sulfide chimney in the hydrothermal field of Suiyo Seamount (Izu-Bonin Arc, Western Pacific). Cells of the isolate were rod-shaped and tended to form a chain-link circular structure (a rotund body) at exponential phase under good growth conditions. The isolate was a chemoheterotroph requiring yeast extract for growth. Although strain St55B T used oxygen as an electron acceptor, it could not form colonies in an oxygen concentration of more than 5 % (v/v). The isolate also used nitrate, nitrite or elemental sulfur in the absence of oxygen. A phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was closely related to Oceanithermus profundus, belonging to the phylum 'Deinococcus-Thermus' (sequence similarity 99?5 %). However, strain St55B T differed from O. profundus in terms of usage of electron donors, cellular fatty acid profile and DNA G+C content. In addition, a DNA-DNA hybridization test indicated low relatedness between the isolate and O. profundus. For the reasons given above, the name Oceanithermus desulfurans sp. nov. is proposed for strain St55BDeep-sea hydrothermal vents have been discovered globally. In such environments, there are the peculiar ecosystems that are completely independent of sunlight and which include thermophilic chemoautotrophs as primary producers. Chimney structures and neighbouring sulfide mounds in hydrothermal areas are able to support metabolically diverse micro-organisms because of the fact that mixing of reduced hydrothermal fluid with oxic deep-sea water provides sharp physical and chemical gradients. Culture-independent analyses based on a 16S rRNA gene clone sequence revealed that various micro-organisms inhabit such environments (Corre et al., 2001;Marteinsson et al., 1995;Takai & Horikoshi, 1999;Takai et al., 2001Takai et al., , 2003. In recent years, many novel thermophilic bacteria have been found in and around these hydrothermal vents (Alain et al., 2002b; Götz et al., 2002;Huber et al., 2002;Jeanthon et al., 2002; Miroshnichenko et al., 2003a, b;Nakagawa et al., 2003;Sako et al., 2003;Vetriani et al., 2004; Wery et al., 2001). , 2003b). These novel species of the Thermaceae, recently proposed in rapid succession, are all 'true' marine organisms that require NaCl for growth. Before these marine species were found, all species in this family (belonging to the genera Thermus and Meiothermus) were inhabitants of freshwater environments, or were isolated from marine environments but were merely halotolerant and not halophilic (Marteinsson et al., 1995). These marine species were rod-shaped micro-organisms able to grow by respiration with oxygen as a terminal electron acceptor. However, the two species O. profundus and V. mediatlanticus are relatively sensitive to oxygen, and grow well at oxygen concentrations of less than 6 % (v/v) and 4-8 % (v/v), respectively (Miroshnichenko et al., 2003a, b). The microaerophiles are also able to u...

From Metagenomics to Pure Culture: Isolation and Characterization of the Moderately Halophilic Bacterium Spiribacter salinus gen. nov., sp. nov

“…Some of the spirals were surrounded by an external envelope, as observed in Fig. 4B and D. These resembled the rotund bodies often observed in Vibrio marinus (46), Oceanithermus (47,48), and some species of the genus Thermus, such as Thermus aquaticus (49), and in a regulation-defective S-layer mutant of Thermus thermophilus, in which round multicellular bodies surrounded by a common envelope were observed as the culture approached the stationary phase (50,51). However, in strain M19-40 T , it seems that only a single spiral cell is included within such an envelope.…”

Complete genome sequence of the aerobic, heterotroph Marinithermus hydrothermalis type strain (T1T) from a deep-sea hydrothermal vent chimney

“…Growth was not observed in anaerobic or autotrophic culture conditions [1]. However, it should be noted that according to Mori and colleagues [32] this was tested only in the presence of sulfide. Steinsbu and colleagues [3] argue that it is therefore possible that M. hydrothermalis has the capability of anaerobic growth under unreduced conditions, as has been observed for Rhabdothermus arcticus , Vulcanithermus mediatlanticus , O. profundus and O. desulfurans [3,32-34].…”

Complete genome sequence of Oceanithermus profundus type strain (506T)

“…The presence of unsaturated branched-chain fatty acids is a distinctive feature of members of the genera Oceanithermus, Vulcanithermus and Rhabdothermus within the family Thermaceae . The unsaturated fatty acid content of the isolate is also higher (33-37%) as compared to the closest relative O. desulfurans (18%) [3]. …”

“…Together with O. desulfurans , there are currently two species placed in the genus [1,3]. The generic name derives from the Latin noun oceanus, meaning ocean and the Neo-Latin masc.…”

“…There are no further cultivated strains of this species known. The other member of the genus, O. desulfurans, is a thermophilic, sulfur-reducing bacterium isolated from a sulfide chimney in Suiyo Seamount, in the Western Pacific [3]. Here we present a summary classification and a set of features for O. profundus 506 T , together with the description of the complete genomic sequencing and annotation.…”