Carboxydobrachium pacificum gen. nov., sp. nov., a new anaerobic, thermophilic, CO-utilizing marine bacterium from Okinawa Trough.

Abstract

A new anaerobic, thermophilic, CO-utilizing marine bacterium, strain JM T , was isolated from a submarine hot vent in Okinawa Trough. Cells of strain JM T were non-motile thin straight rods, sometimes branching, with a cell wall of the Gram-positive type, surrounded with an S-layer. Chains of three to five cells were often observed. The isolate grew chemolithotrophically on CO, producing equimolar quantities of H 2 and CO 2 (according to the equation COMH 2 O 4 CO 2 MH 2 ) and organotrophically on peptone, yeast extract, starch, cellobiose, glucose, galactose, fructose and pyruvate, producing H 2 , acetate and CO 2 . Growth was observed from 50 to 80 SC with an optimum at 70 SC. The optimum pH was 68-71. The optimum concentration of sea salts in the medium was 205-255 g l V1 . The generation time under optimal conditions was 71 h. The DNA GMC content was 33 mol %. Growth of isolate JM T was not inhibited by penicillin, but ampicillin, streptomycin, kanamycin and neomycin completely inhibited growth. The results of 16S rDNA sequence analysis revealed that strain JM T belongs to the Thermoanaerobacter phylogenetic group within the Bacillus-Clostridium subphylum of Gram-positive bacteria but represents a separate branch of this group. On the basis of morphological and physiological features and phylogenetic data, this isolate should be assigned to a new genus, for which the name Carboxydobrachium is proposed. The type species is Carboxydobrachium pacificum ; the type strain is JM T (l DSM 12653 T ).Keywords : submarine hot vents, carbon monoxide utilization, thermophilic anaerobe, Carboxydobrachium pacificum INTRODUCTIONDeep-sea hydrothermal fields are inhabited by unique microbial communities that rely on the energy of reduced inorganic compounds of volcanic origin (Jannasch, 1995). Many thermophilic prokaryotes have been isolated from such habitats over the past decade . However, most of these organisms were hyperthermophilic archaea of the Euryarchaeota and Crenarchaeota kingdoms. Among them were methanogens of genera Methanopyrus (Kurr et al., 1991) and Methanococcus (Jones et al., 1983 ;Jeanthon et al., 1998) reducers of the genus Archaeoglobus (Burggraf et al., 1990 ; Huber et al., 1997) ; Pyrolobus fumarii, oxidizing molecular hydrogen either aerobically or via nitrate reduction (Blo$ chl et al., 1997) ; and numerous anaerobic organotrophs belonging to the genera Staphylothermus (Fiala et al., 1986), Thermococcus (Kobayshi et al., 1994 ; Gonza! lez et al., 1995, etc.), Pyrococcus (Erauso et al., 1993 ; Gonza! lez et al., 1998) and Pyrodictium (Pley et al., 1991). The information on the presence of thermophilic bacteria in the microbial communities of deep-sea hot vents is up to now much more sparse. The presence of organotrophic anaerobes and aerobes belonging to the genera Thermotoga, Thermus and Bacillus in deep-sea hydrothermal habitats has been reported (Marteinsson et al., 1995(Marteinsson et al., , 1996a T. G. Sokolova and others esiensis has been isolated in pure culture (Antoine et al., 1997). ...

Thermosinus carboxydivorans gen. nov., sp. nov., a new anaerobic, thermophilic, carbon-monoxide-oxidizing, hydrogenogenic bacterium from a hot pool of Yellowstone National Park

“…Determinations of CO, gaseous products of metabolism, short-chain organic acids and alcohols were performed by GC as described previously (Sokolova et al, 2001). H 2 S was determined by colorimetric reaction (Trüper & Schlegel, 1964).…”

“…Carboxydothermus hydrogenoformans was the first anaerobic, thermophilic, non-photosynthetic bacterium found that performed this process (Svetlichny et al, 1991). Later, several other organisms performing the reaction of anaerobic CO oxidation with CO 2 and H 2 production were described (Svetlichny et al, 1994;Sokolova et al, 2001Sokolova et al, , 2004. Strain Nor1 T is similar to Caldanaerobacter subterraneus subsp.…”

“…Strain Nor1 T is similar to Caldanaerobacter subterraneus subsp. pacificus (formerly Carboxydibrachium pacificum) (Sokolova et al, 2001;Fardeau et al, 2004) in its ability to ferment some carbohydrates. However, they differ in the ability to reduce ferric iron.…”

“…These are representatives of the bacterial genera Carboxydothermus (Svetlichny et al, 1991(Svetlichny et al, , 1994, Caldanaerobacter (formerly Carboxydibrachium pacificum) (Sokolova et al, 2001;Fardeau et al, 2004) and Carboxydocella (Sokolova et al, 2002). Recently, a hyperthermophilic archaeon of the genus Thermococcus capable of growth at the expense of the same reaction was isolated from deepsea hydrothermal vents (Sokolova et al, 2004).…”

“…Caldanaerobacter subterraneus subsp. pacificus, isolated from a deep-sea hydrothermal vent in the Okinawa Trough, besides having the capacity for anaerobic CO oxidation/H 2 formation, is capable of growing on several fermentable substrates (Sokolova et al, 2001). Thermococcus strain AM4 grows on CO producing H 2 , or chemo-organotrophically with elemental sulfur (Sokolova et al, 2004).…”