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1 Subground Animalcule Retrieval (SUGAR) Project, Frontier Research System for Extremophiles, Japan Marine Science & Technology Center, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan
2 Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy, Los Angeles, CA 90089-0740, USA
Correspondence
Ken Takai
kent{at}jamstec.go.jp
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Published online ahead of print on 12 December 2003 as DOI 10.1099/ijs.0.02887-0.
The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain Mc-S-70T is AB100884.
Graphs showing the effects of temperature, pH and NaCl concentration on growth of Methanotorris formicicus are available as supplementary figures A, B and C, respectively, in IJSEM Online.
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TOPABSTRACTMAIN TEXTREFERENCES |
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; Huber et al., 1982; Jeanthon et al., 1998, 1999a, b; Jones et al., 1983b, 1989; L'Haridon et al., 2003; Stetter, 1996; Takai et al., 2002; Zhao et al., 1988). A number of strains from deep-sea hydrothermal environments have recently been added to the list: Methanocaldococcus jannaschii strain JAL-1T, Methanocaldococcus vulcanius strain M7T, Methanocaldococcus fervens strain AG86T and Methanocaldococcus infernus strain MET were isolated from the East Pacific Rise, Guaymas Basin and the Mid-Atlantic Ridge (MAR) (Jeanthon et al., 1998, 1999a; Jones et al., 1983b, 1989; Zhao et al., 1988); Methanocaldococcus indicus strain SL43T from the Central Indian Ridge (CIR) (L'Haridon et al., 2003); and Methanothermococcus okinawensis strain IH1T from the Western Pacific Okinawa Trough (Takai et al., 2002). Although physiological and molecular properties have not been described, Jeanthon et al. (1999b) have also succeeded in isolating many hyperthermophilic methanogens potentially belonging to the genus Methanotorris from deep-sea hydrothermal environments in the Guaymas Basin and MAR.
Historically, the systematics of methanococci has been hindered by the absence of information on the reliability of phenotypic characters (Keswani et al., 1996). Recently, Whitman et al. (2001) reclassified the order Methanococcales based on a polyphasic taxonomic characterization. The newly proposed classification fits well with phylogenetic relationships associated with thermophilic behaviour among the order Methanococcales, and the subsequent isolation of a novel species of the genus Methanothermococcus has strengthened the phylogenetic affiliation of members of the genus Methanothermococcus (Takai et al., 2002). However, the genus Methanotorris is still represented by only one species, Methanotorris igneus strain Kol 5T, which was isolated from a coastal hydrothermal environment in Iceland (Burggraf et al., 1990). In addition, none of the extremely thermophilic members, which are defined as micro-organisms capable of growth above 80 °C and optimally above 70 °C, has been obtained from any habitat, although many hyperthermophilic or thermophilic entities are listed in the order Methanococcales (L'Haridon et al., 2003; Takai et al., 2002; Whitman et al., 2001). In this study, an extremely thermophilic strain of the genus Methanotorris was isolated from a black smoker chimney at the Kairei field in the CIR.
Samples from a black smoker vent were obtained from the Kairei field, CIR (25° 19·23'S; 70° 02·42'E), at a depth of 2421 m by the manned submersible Shinkai 6500 in a dive (dive no. 659) performed in February 2002. The Kairei hydrothermal field in the CIR was discovered by Japanese scientists in 2000 (Hashimoto et al., 2001). A bulk chimney sample with a vent emission temperature of >250 °C was brought to the sea surface in a sample box, which is part of the equipment of the Shinkai 6500, and immediately divided into two sections (surface layer of the chimney and vent orifice surface) as described by Takai et al. (2001). The chimney was mainly composed of crystalline or amorphous chalcopyrite. Each of the subsample sections (approx. 10 g) was suspended in 20 ml sterilized MJ synthetic sea water (Takai et al., 1999) containing 0·05 % (w/v) sodium sulfide in a 100 ml glass bottle (Schott Glaswerke) and tightly sealed with a butyl rubber cap under a gas phase of 100 % N2 (100 kPa). These suspended portions of the subsamples were inoculated (0·1 % volume of the medium) onto MMJ medium (Takai et al., 2002) with 5 mM CaCl2 under a gas phase of 80 % H2 and 20 % CO2 (300 kPa). The cultures were incubated at 70 and 85 °C in dry ovens onboard.
Growth of hyperthermophilic or thermophilic micro-organisms was observed in MMJ medium with 5 mM CaCl2 after 2 days incubation at both 70 and 85 °C. Based on DAPI (4',6-diamidino-2-phenylindole)-stained direct cell counting of the subsamples (Porter & Feig, 1980), the chimney surface layer contained 8·9x107 cells (g wet weight)–1, whereas the vent orifice surface had 1·0x105 cells (g wet weight)–1. These results were similar to previously demonstrated results on a black smoker chimney structure from the Manus Basin deep-sea hydrothermal field (Takai et al., 2001). All enrichment cultures grown at 70 and 85 °C contained highly motile or non-motile irregular cocci. Since these irregular cocci had autofluorescence under UV- and blue-excitation by epifluorescence microscopy, the hyperthermophiles or thermophiles were probably methanogens, most likely members of the order Methanococcales. Characterization of the gas phase after growth using a GC (Micro GC CP2002; GL Sciences) revealed that methanogenesis occurred in all enrichment cultures grown at 70 and 85 °C. Pure cultures were obtained using the dilution-to-extinction technique at 70 or 85 °C with the same medium used for the enrichment (Takai & Horikoshi, 2000). At least five series of dilution-to-extinction purifications were performed. The partial sequence of the 16S rRNA gene from each of the isolates was determined and used for sequence similarity analysis as described previously (Takai et al., 2001). One strain, designated Mc-S-70T, was characterized further. The purity of the isolate was confirmed routinely by microscopic examination and by repeated partial sequencing of the 16S rRNA gene using several PCR primers (Lane, 1985). Potential contamination of heterotrophic thermophiles was also tested using media for strict heterotrophs such as MJYP and MJYPS (Takai et al., 2000).
Cells were routinely observed under a phase-contrast Olympus BX51 microscope with the SPOT RT Slider CCD camera system (Diagnostic Instruments). Transmission electron microscopy of negatively stained cells and thin sections of cells was carried out as described by Zillig et al. (1990). Cells grown in MMJ medium supplemented with 5 mM CaCl2 at 70 °C in the mid-exponential phase of growth were negatively stained with 2 % (w/v) uranyl acetate and observed under a JEOL JEM-1210 electron microscope at an accelerating voltage of 120 kV. Cells of strain Mc-S-70T were Gram-negative, irregular cocci, which were about 0·8–1·5 µm diameter in the exponential growth phase (Fig. 1a, b). Motility was not evident in laboratory cultures, although several thin, long flagella were observed by electron microscopy (Fig. 1a). These morphological features were quite similar to those of Methanotorris igneus strain Kol 5T (Burggraf et al., 1990). In static culture with MMJ medium supplemented with 5 mM CaCl2, strain Mc-S-70T grew as an aggregate without causing turbidity in the liquid. Formation of an aggregate in static culture might be associated with non-motility of strain Mc-S-70T. This was a distinctive growth characteristic, which was not common among other Methanococcales strains tested (Methanocaldococcus jannaschii strain JAL-1T, Methanotorris igneus strain Kol 5T, Methanothermococcus okinawensis strain IH1T, Methanothermococcus thermolithotrophicus strain SN-1T and Methanococcus maripaludis strain JJT). Methanocaldococcus jannaschii strain JAL-1T (=JCM 10045T), Methanothermococcus thermolithotrophicus strain SN-1T (=JCM 10549T) and Methanococcus maripaludis strain JJT (=JCM 10722T) were obtained from the Japan Collection of Microorganisms (Wako, Japan) and Methanotorris igneus strain Kol 5T (=DSM 5666T) was purchased from the Deutsche Sammlung von Mikrooganismen und Zellkulturen (Braunschweig, Germany). All strains were cultivated under optimal conditions, as described previously (Burggraf et al., 1990; Huber et al., 1982; Jones et al., 1983a, b; Takai et al., 2002).
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) using an Olympus BX51 microscope with the SPOT RT Slider CCD camera system. All experiments described below were conducted in duplicate.
Strain Mc-S-70T grew only under strictly anaerobic culture conditions and was strongly sensitive to oxygen. It was an autotrophic methanogen utilizing hydrogen and carbon dioxide as the sole energy and carbon sources. During growth, hydrogen and carbon dioxide levels in the headspace gas decreased and methane was produced (approx. 100 p.p.m. H2, 3000 p.p.m. CO2 and 95 % CH4 in the gas phase after 2 days incubation). The maximum cell yield in the presence of H2 and CO2 in MMJ medium with 5 mM CaCl2 was 5·0x108 cells ml–1. If the concentration of calcium ions in MMJ medium was decreased to 0·2 mM, the maximum cell yield was reduced to 7·0x107 cells ml–1. Mc-S-70T grew on formate (10 mM) in the absence of H2 (8·0x107 cells ml–1 after 2 days incubation) in MMJ medium with 5 mM CaCl2, indicating that strain Mc-S-70T was able to utilize formate as an alternative energy source. Acetate (20 mM), methanol (0·05 %, v/v), ethanol (0·05 %, v/v), dimethyl sulfide (0·2 % v/v), trimethylamine (0·2 %, v/v), yeast extract (0·02 %, w/v), peptone (0·02 %, w/v), tryptone (0·02 %, w/v), Casamino acids (0·02 %, w/v) and an amino acid mixture (containing 0·001 %, w/v, each of 20 amino acids) did not replace the growth requirement for H2 or stimulate growth in the presence of H2 and CO2. The following nitrogen sources were used to replace the 5 mM ammonium ion in MMJ medium (with 220 kPa H2 and 80 kPa CO2 in the gas phase): 5 mM nitrate; 0·5 mM nitrite; and 100 kPa N2. Ammonium ion was the most effective nitrogen source: the maximum cell yield obtained was 5·0x108 cells ml–1. Both nitrate and N2 also served as nitrogen sources and their maximum cell yields were 1·6x108 and 2·4x108 cells ml–1, respectively. Nitrite did not serve as a nitrogen source. The presence of 10 mM magnetite (Fe3O4) and 10 mM thiosulfate (
) had no effect on growth and 3 % (w/v) elemental sulfur (S0) slightly inhibited growth. Selenium, tungsten and vitamin mixture were neither stimulatory nor required for growth. Utilization of formate as a growth substrate and methanogenesis were distinctive features of strain Mc-S-70T compared to Methanotorris igneus strain Kol 5T.
The effects of temperature, pH and NaCl concentration on growth were tested. With MMJ medium supplemented with 5 mM CaCl2, strain Mc-S-70T grew at 55–83 °C, showing optimal growth at 75 °C; the generation time at 75 °C and pH 6·7 was about 30 min (see Fig. A, available as supplementary material in IJSEM Online). No growth was observed at 45 or 85 °C. To determine the effect of pH on growth, the pH of MMJ medium containing 5 mM CaCl2 was adjusted to various levels with 10 mM acetate/acetic acid buffer (pH 4·0–5·0), MES (pH 5·0–6·0), PIPES (pH 6·0–7·0), HEPES (pH 7·0–7·5) and Tris (pH 8·0–9·5). Growth of strain Mc-S-70T at 70 °C occurred at pH 6·0–8·5, with optimum growth at about pH 6·7 (see Fig. B, available as supplementary material in IJSEM Online). The pH was stable during the cultivation period. The effect of NaCl concentration on growth was determined using MMJ medium with 5 mM CaCl2 containing different amounts of NaCl. Strain Mc-S-70T grew in 4–60 g NaCl l–1, with optimum growth at 24 g NaCl l–1, 70 °C and pH 6·7 (see Fig. C, available as supplementary material in IJSEM Online). Compared with Methanotorris igneus strain Kol 5T, strain Mc-S-70T had a lower optimal growth temperature, a lower shifted growth temperature range and a slightly higher shifted pH range.
The sensitivity of strain Mc-S-70T to antibiotics such as chloramphenicol (50, 100 and 200 µg ml–1), streptomycin (100 and 200 µg ml–1), kanamycin (100 and 200 µg ml–1), ampicillin (100 and 200 µg ml–1) and rifampicin (50 and 100 µg ml–1) was tested at 70 °C. A simultaneous experiment was performed with Methanotorris igneus strain Kol 5T at 80 °C. Methanotorris igneus strain Kol 5T and strain Mc-S-70T showed the same antibiotic resistance pattern. Both strains were resistant to streptomycin (up to 200 µg ml–1), kanamycin (up to 200 µg ml–1) and rifampicin (up to 50 µg ml–1), but sensitive to chloramphenicol (50 µg ml–1) and rifampicin (100 µg ml–1). Susceptibility to lysis by SDS and a hypotonic solution was tested as described previously (Boone & Whitman, 1988). Cells of strain Mc-S-70T lysed with 0·1 % (w/v) SDS solution and hypotonic solutions [10–1 diluted MJ(–N) synthetic sea water (Takai et al., 2000) and distilled water].
Hydrocarbon chains in core ether lipids were analysed by a combined method described by Koga et al. (1993) and DeLong et al. (1998). Total lipid was extracted from lyophilized cells of strain Mc-S-70T (50 mg) harvested in late-exponential growth phase by the method of Nishihara & Koga (1987) and Koga et al. (1993). Then, hydrocarbon chains were prepared by HI degradation followed by LiAlH4 reduction as described by DeLong et al. (1998). The resulting hydrocarbons were analysed by GLC (model GC-380; GL-Science) equipped with a mass spectrometer (GCMS-QP5050; Shimadzu) at a temperature increasing from 100 to 320 °C at a rate of 4 °C min–1. A simultaneous experiment was performed with Methanotorris igneus strain Kol 5T, Methanocaldococcus jannaschii strain JAL-1T and Methanothermococcus okinawensis strain IH1T. The hydrocarbon chains of strain Mc-S-70T were C20 (76·9 %), derived from archaeol and hydroxyarchaeol, and C40 (23·1 %), derived from caldarchaeol and cyclic archaeol. No C40 isoprenoid containing cyclopentane and cyclohexane rings was detected in strain Mc-S-70T. Compared to hydrocarbons in Methanotorris igneus strain Kol 5T (C20, 55·4 %; C40, 44·6 %), Methanocaldococcus jannaschii strain JAL-1T (C20, 19·6 %; C40, 80·4 %) and Methanothermococcus okinawensis strain IH1T (C20, 37·8 %; C40, 63·2 %), a lower proportion of C40 isoprenoid was found in strain Mc-S-70T.
Genomic DNA of strain Mc-S-70T was prepared as described by Marmur & Doty (1962). The DNA G+C content was determined by direct analysis of deoxyribonucleotides by HPLC (Tamaoka & Komagata, 1984). The G+C content of the genomic DNA of strain Mc-S-70T was 33·3 mol%, which is slightly higher than that of Methanotorris igneus strain Kol 5T (Table 1).
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; Lane, 1985) as described previously (Takai et al., 2002). The nearly complete sequence (1374 bp) of the 16S rRNA gene from strain Mc-S-70T was directly sequenced from both strands using the dideoxynucleotide chain-termination method with a DNA sequencer model 3100 (Perkin Elmer/Applied Biosystems). The 16S rRNA gene sequence was analysed using the gapped-BLAST search algorithm (Altschul et al., 1997; Benson et al., 1998) and was most closely related (97·8 %) to that of Methanotorris igneus strain Kol 5T (Burggraf et al., 1990). This suggested that strain Mc-S-70T belongs to the genus Methanotorris.
The nearly complete sequence was manually realigned to 16S rRNA gene data from the Ribosomal Data Project II (Maidak et al., 2000), based on alignments determined using the SEQUENCE ALIGNER program of RDP-II. Phylogenetic analyses were restricted to nucleotide positions that could be unambiguously aligned. Evolutionary distance matrix analysis (using the Kimura two-parameter method, the least-squares distance method and transition/transversion rate of 2·0) and neighbour-joining analysis were performed using the PHYLIP package (version 3.5; obtained from J. Felsenstein, University of Washington, Seattle, WA, USA) (Fig. 2). Bootstrap analysis was performed to provide confidence estimates for phylogenetic tree topologies. The phylogenetic tree indicated that strain Mc-S-70T is closely related to Methanotorris igneus strain Kol 5T, as determined by sequence similarity analysis (Fig. 2).
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. The mean hybridization value was 5·1 %, indicating that strain Mc-S-70T could be genotypically differentiated from the previously described species of the genus Methanotorris.
Strain Mc-S-70T was isolated from a black smoker chimney of a deep-sea hydrothermal vent at a depth of 2421 m at the Kairei field, CIR. Phylogenetic analysis indicated that strain Mc-S-70T is most closely related to Methanotorris igneus strain Kol 5T, which was isolated from a coastal hydrothermal environment in Iceland (Burggraf et al., 1990), and was probably a member of the genus Methanotorris. However, many of the physiological characteristics of strain Mc-S-70T differed from those of Methanotorris igneus strain Kol 5T (Table 1
). Strain Mc-S-70T is the first extreme thermophile found within the order Methanococcales that grows optimally at 75 °C, which is approximately 10 °C lower than the optimum of Methanotorris igneus strain Kol 5T (Table 1). In addition, Methanotorris igneus strain Kol 5T is known as the most acidiphilic thermophilic methanogen (Wiegel, 2002), having an optimal pH for growth of pH 5·7, whereas strain Mc-S-70T grows optimally at neutral pH (Table 1). Another distinctive feature is the utilization of formate as a substrate for growth and methanogenesis in strain Mc-S-70T (Table 1). All the hyperthermophilic members of the order Methanococcales known so far, other than a hyperthermophilic isolate (strain CS-1) from the Guaymas Basin (Jones et al., 1989), are unable to use formate as a sole energy source (Whitman et al., 2001). In sharp contrast, all thermophilic and mesophilic entities of the order Methanococcales can utilize formate as a sole energy source, providing a similar growth yield to H2 (Whitman et al., 2001). In strain Mc-S-70T, formate gives considerably lower growth yield than H2, but can serve as an alternative energy source (Table 1). The extremely thermophilic behaviour and formate utilization of strain Mc-S-70T are important physiological features that support genetic differentiation between strain Mc-S-70T and Methanotorris igneus strain Kol 5T by DNA–DNA relatedness. These may also represent intermediate traits during evolution of the order Methanococcales from hyperthermophile to mesophile. On the basis of these physiological and genetic properties, it is proposed that the isolate is classified as a novel species of the genus Methanotorris, Methanotorris formicicus sp. nov., with Mc-S-70T as the type strain.
Description of Methanotorris formicicus sp. nov.
Methanotorris formicicus (for.mi'ci.cus. N.L. neut. n. acidum formicum formic acid; N.L. neut. adj. formicicus pertaining to formic acid).
Irregular coccus, mean diameter of 0·8–1·5 µm. Cells occur singly or in pairs. Non-motile, but with a few thin, long flagella, which are easily removed from the cell. Strictly anaerobic and obligately methanogenic. The temperature range for growth is 55–83 °C (optimum of 75 °C). The pH range for growth is pH 6·0–8·5 (optimum of pH 6·7). NaCl is required for growth, which occurs in 4–60 g NaCl l–1 (optimum growth at 24 g l–1). Grows using molecular hydrogen or formate as an electron donor and carbon dioxide as an electron acceptor and a carbon source. Ammonium, molecular nitrogen and nitrate serve as nitrogen sources. Vitamins, selenium, tungsten, magnetite (Fe3O4) and thiosulfate do not stimulate growth. Resistant to ampicillin (200 µg ml–1), kanamycin (200 µg ml–1), rifampicin (50 µg ml–1) and streptomycin (200 µg ml–1), but sensitive to chloramphenicol (50 µg ml–1) and rifampicin (100 µg ml–1). Susceptible to lysis by 0·1 % (w/v) SDS solution and hypotonic solutions. Major hydrocarbon chains of core lipids are C20 (76·9 %) and C40 (23·1 %). 16S rRNA gene sequence exhibits 97·8 % similarity to that of Methanotorris igneus strain Kol 5T. DNA–DNA relatedness to Methanotorris igneus strain Kol 5T is low.
The type strain is Mc-S-70T (=JCM 11930T=ATCC BAA-687T), isolated from a black smoker chimney in the Kairei field, Central Indian Ridge, Indian Ocean. Its genomic DNA G+C content is 33·3 % (HPLC method).
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ACKNOWLEDGEMENTS |
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REFERENCES |
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TOPABSTRACTMAIN TEXTREFERENCES |
|---|
Benson, D. A., Boguski, M. S., Lipman, D. J., Ostell, J. & Ouellette, B. F. F. (1998). GenBank. Nucleic Acids Res 26, 1–7.
Boone, D. R. & Whitman, W. B. (1988). Proposal of minimal standards for describing new taxa of methanogenic bacteria. Int J Syst Bacteriol 38, 212–219.
Burggraf, S., Fricke, H., Neuner, A., Kristjansson, J. K., Rouvier, P., Mandelco, L., Woese, C. R. & Stetter, K. O. (1990). Methanococcus igneus sp. nov., a novel hyperthermophilic methanogen from a shallow submarine hydrothermal system. Syst Appl Microbiol 13, 263–269.[Medline]
DeLong, E. F. (1992). Archaea in coastal marine environments. Proc Natl Acad Sci U S A 89, 5685–5689.
DeLong, E. F., King, L. L., Massana, R., Cittone, H., Murray, A., Schleper, C. & Wakeham, G. (1998). Dibiphytanyl ether lipids in nonthermophilic crenarchaeotes. Appl Environ Microbiol 64, 1133–1138.
Ezaki, T., Hashimoto, Y. & Yabuuchi, E. (1989). Fluorometric deoxyribonucleic acid-deoxyribonucleic acid hybridization in microdilution wells as an alternative to membrane filter hybridization in which radioisotopes are used to determine genetic relatedness among bacterial strains. Int J Syst Bacteriol 39, 224–229.
Hashimoto, J., Ohta, S., Gamo, T. & 7 other authors (2001). First hydrothermal vent communities from the Indian Ocean discovered. Zool Sci 18, 717–721.[CrossRef]
Huber, H., Thomm, M., König, H., Thies, G. & Stetter, K. O. (1982). Methanococcus thermolithotrophicus, a novel thermophilic lithotrophic methanogen. Arch Microbiol 132, 47–50.[CrossRef]
Jeanthon, C., L'Haridon, S., Reysenbach, A. L., Vernet, M., Messner, P., Sleytr, U. B. & Prieur, D. (1998). Methanococcus infernus sp. nov., a novel hyperthermophilic lithotrophic methanogen isolated from a deep-sea hydrothermal vent. Int J Syst Bacteriol 48, 913–919.
Jeanthon, C., L'Haridon, S., Reysenbach, A.-L., Corre, E., Vernet, M., Messner, P., Sleytr, U. B. & Prieur, D. (1999a). Methanococcus vulcanius sp. nov., a novel hyperthermophilic methanogen isolated from East Pacific Rise, and identification of Methanococcus sp. DSM 4213T as Methanococcus fervens sp. nov. Int J Syst Bacteriol 49, 583–589.
Jeanthon, C., L'Haridon, S., Pradel, N. & Prieur, D. (1999b). Rapid identification of hyperthermophilic methanococci isolated from deep-sea hydrothermal vents. Int J Syst Bacteriol 49, 591–594.
Jones, W. J., Paynter, M. J. B. & Gupta, R. (1983a). Characterization of Methanococcus maripaludis sp. nov., a new methanogen isolated from salt marsh sediment. Arch Microbiol 135, 91–97.[CrossRef]
Jones, W. J., Leigh, J. A., Mayer, F., Woese, C. R. & Wolfe, R. S. (1983b). Methanococcus jannaschii sp. nov., an extremely thermophilic methanogen from a submarine hydrothermal vent. Arch Microbiol 136, 254–261.[CrossRef]
Jones, W. J., Stugard, C. E. & Jannasch, H. W. (1989). Comparison of thermophilic methanogens from submarine hydrothermal vents. Arch Microbiol 151, 314–318.[CrossRef]
Keswani, J., Orkand, S., Premachandran, U., Mandelco, L., Franklin, M. J. & Whitman, W. B. (1996). Phylogeny and taxonomy of mesophilic Methanococcus spp. and comparison of rRNA, DNA hybridization, and phenotypic methods. Int J Syst Bacteriol 46, 727–735.
Koga, Y., Akagawa-Matsushita, M., Ohga, M. & Nishihara, M. (1993). Taxonomic significance of the distribution of component parts of polar ether lipids in methanogens. Syst Appl Microbiol 16, 342–351.
Lane, D. J. (1991). 16S/23S rRNA sequencing. In Nucleic Acid Techniques in Bacterial Systematics, pp. 115–175. Edited by E. Stackebrandt & M. Goodfellow. Chichester: John Wiley.
L'Haridon, S., Reysenbach, A.-L., Banta, A., Messner, P., Schumann, P., Stackebrandt, E. & Jeanthon, C. (2003). Methanocaldococcus indicus sp. nov., a novel hyperthermophilic methanogen isolated from the Central Indian Ridge. Int J Syst Evol Microbiol 53, 1931–1935.
Maidak, B. L., Cole, J. R., Lilburn, T. G. & 9 other authors (2000). The RDP (Ribosomal Database Project) continues. Nucleic Acids Res 28, 173–174.
Marmur, J. & Doty, P. (1962). Determination of the base composition of deoxyribonucleic acid from its thermal denaturation temperature. J Mol Biol 4, 109–118.
Nishihara, M. & Koga, Y. (1987). Extraction and composition of polar lipids from the archaebacterium, Methanobacterium thermoautotrophicum: effective extraction of tetraether lipids by an acidified solvent. J Biochem Tokyo 101, 997–1005.
Porter, K. G. & Feig, Y. S. (1980). The use of DAPI for identifying and counting microflora. Limnol Oceanogr 25, 943–948.
Stetter, K. O. (1996). Hyperthermophilic procaryotes. FEMS Microbiol Rev 18, 149–158.[CrossRef]
Takai, K. & Horikoshi, K. (2000). Thermosipho japonicus sp. nov., an extremely thermophilic bacterium isolated from a deep-sea hydrothermal vent in Japan. Extremophiles 4, 9–17.[Medline]
Takai, K., Inoue, A. & Horikoshi, K. (1999). Thermaerobacter marianensis gen. nov., sp. nov., an aerobic extremely thermophilic marine bacterium from the 11 000 m deep Mariana Trench. Int J Syst Bacteriol 49, 619–628.
Takai, K., Sugai, A., Itoh, T. & Horikoshi, K. (2000). Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney. Int J Syst Evol Microbiol 50, 489–500.[Abstract]
Takai, K., Komatsu, T., Inagaki, F. & Horikoshi, K. (2001). Distribution of archaea in a black smoker chimney structure. Appl Environ Microbiol 67, 3618–3629.
Takai, K., Inoue, A. & Horikoshi, K. (2002). Methanothermococcus okinawensis sp. nov., a thermophilic, methane-producing archaeon isolated from a Western Pacific deep-sea hydrothermal vent system. Int J Syst Evol Microbiol 52, 1089–1095.[Abstract]
Tamaoka, J. & Komagata, K. (1984). Determination of DNA base composition by reversed-phase high-performance liquid chromatography. FEMS Microbiol Lett 25, 125–128.
Whitman, W. B., Boone, D. R. & Koga, Y. (2001). Order Methanococcales. In Bergey's Manual of Systematic Bacteriology, 2nd edn, vol. 1, pp. 236–246. Edited by D. R. Boone, R. W. Castenholz & G. Garrity. Berlin/Heidelberg, Germany: Springer.
Wiegel, J. (2002). Thermophiles: anaerobic alkalithermophiles. In Encyclopedia of Environmental Microbiology, pp. 3127–3140. Edited by G. Bitton. New York: Wiley.
Zhao, H., Wood, A. G., Widdel, F. & Bryant, M. P. (1988). An extremely thermophilic Methanococcus from a deep-sea hydrothermal vent and its plasmid. Arch Microbiol 150, 178–183.[CrossRef]
Zillig, W., Holz, I., Janekovic, D. & 7 other authors (1990). Hyperthermus butylicus, a hyperthermophilic sulfur-reducing archaebacterium that ferments peptides. J Bacteriol 172, 3959–3965.
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