Methanocaldococcus indicus sp. nov., a novel hyperthermophilic methanogen isolated from the Central Indian Ridge

Abstract

An autotrophic, hyperthermophilic methanogen, strain SL43 T , was isolated from a deep-sea hydrothermal chimney sample collected on the Central Indian Ridge at a depth of 2420 m. The coccoid, surface-layer-carrying, Gram-negative-staining cells were heavily flagellated and exhibited a slight tumbling motility. The temperature range for growth at pH 6?5 was 50-86 6C, with optimum growth at 85 6C. The optimum pH for growth was 6?6 and the optimum NaCl concentration for growth was 30 g l "1 . The novel isolate used H 2 and CO 2 as the only substrates for growth and produced methane. Selenium and yeast extract stimulated growth significantly. In the presence of CO 2 and H 2 , the organism reduced elemental sulfur to hydrogen sulfide. Growth was inhibited by chloramphenicol and rifampicin, but not by ampicillin, kanamycin, penicillin or streptomycin. The G+C content of the genomic DNA was 30?7 mol%. On the basis of 16S rRNA gene sequence analysis, this organism was most closely related to Methanocaldococcus infernus ME T (3?2 % distance). Its phylogenetic distinctiveness was confirmed by RFLP analysis of the 16S rDNA, a reliable tool for differentiating hyperthermophilic methanococci. On the basis of phylogenetic and physiological characteristics, it is proposed that strain SL43 T (=DSM 15027 T =JCM 11886 T ) be designated as the type strain of a novel species, Methanocaldococcus indicus sp. nov.On the basis of differences in 16S rRNA gene sequences and the diversity of temperature growth ranges, the strictly anaerobic, methane-producing members of the order Methanococcales have recently been separated into two families, the mesophilic and thermophilic members of the Methanococcaceae (optimal temperature ¡70 u C) and the hyperthermophilic members of the Methanocaldococcaceae (Whitman et al., 2001). The family Methanocaldococcaceae includes two new genera, Methanocaldococcus and Methanotorris (Whitman & Jeanthon, 2002). Members of these genera possess less than 93 % 16S rRNA gene sequence similarity and have been exclusively isolated from deep-sea hydrothermal vents. Within the genus Methanocaldococcus, the 16S rRNA sequence similarity between species is greater than 95 %.

Growth kinetics and energetics of a deep‐sea hyperthermophilic methanogen under varying environmental conditions

“…Methanocaldococcus spp. are cosmopolitan members of deep‐sea hydrothermal vent communities that typically grow optimally at 80–85°C (Jones et al ., ; Jeanthon et al ., 1998; 1999a,b; L'Haridon et al ., ; Mehta and Baross, ; Ver Eecke et al ., ). Bioenergetic models of growth and maintenance have been made for hydrogenotrophic methanogenesis between −20°C and 130°C (Hoehler, ).…”

Indian Ocean Hydrothermal Systems: Seafloor Hydrothermal Activities, Physical and Chemical Characteristics of Hydrothermal Fluids, and Vent-Associated Biological Communities

“…Immediately after the discovery of the Kairei hydrothermal field, many new genera and species of deep-sea vent chemolithoautotrophs were isolated and described (L'Haridon et al 2003;Moussard et al 2004;Takai et al 2004cTakai et al , d, 2008. A hyperthermophilic hydrogenotrophic methanogen, Methanocaldococcus indicus (L' Haridon et al 2003), and an extremely thermophilic hydrogenotrophic methanogen, Methanotorris formicicus (Takai et al 2004c), identified in the Kairei hydrothermal field represent new species of Methanococcales and important primary producers of chemolithotrophic microbial communities.…”

Methanocaldococcus villosus sp. nov., a heavily flagellated archaeon that adheres to surfaces and forms cell–cell contacts

“…Methanocaldococcus jannaschii DSM 2661 T (Jones et al, 1983), Methanotorris igneus DSM 5666 T (Burggraf et al, 1990) and Methanothermococcus thermolithotrophicus DSM 2095 T (Huber et al, 1982) were available from our in-house culture collection. Methanocaldococcus fervens DSM 4213 T (Jeanthon et al, 1999), Methanocaldococcus indicus DSM 15027 T (L'Haridon et al, 2003), Methanocaldococcus infernus DSM 11812 T (Jeanthon et al, 1998) and Methanocaldococcus vulcanius DSM 12094 T (Jeanthon et al, 1999) were obtained from the Deutsche Sammlung von Mikroorganismen und Zellkulturen (Braunschweig, Germany). For comparative studies, all strains were grown in MJ medium.…”

“…All strains of the genus Methanocaldococcus described so far have been isolated from deep submarine habitats, e.g. hydrothermally heated material (Zhao et al, 1988) or chimney samples (Jones et al, 1983;Jeanthon et al, 1998Jeanthon et al, , 1999L'Haridon et al, 2003), whereas the genus Methanotorris was originally described from a shallow submarine hydrothermal vent (Burggraf et al, 1990). In general, their requirement for selenium and the high motility of cells allow differentiation of the genus Methanocaldococcus from Methanotorris (Whitman et al, 2001).…”

“…Gram staining and susceptibility to lysis by hypotonic solution and detergents were performed as described previously (Boone & Whitman, 1988). The organism stained Gramnegative, and cells of the mid-to late-exponential growth phase lysed rapidly in distilled water, hypotonic solution or 0.01 % (w/v) SDS, as described for Methanocaldococcus (Jeanthon et al, 1999;L'Haridon et al, 2003).…”