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1Departments of Environmental Science and Engineering
2Chemical and Biological Sciences
3Oregon Graduate Institute of Science & Technology, 19600 N. W. von Neumann Drive, Beaverton, Oregon 97006-1999; School of Public Health, University of California, Los Angeles, California 90024
4LaboratÓrio Nacional de Engenharia e Tecnologia Indústrial, Estrada das Palmeiras, 2745 Queluz, Portugal
* Corresponding author.
ABSTRACT
Six strains of coccoid, halophilic methanogens were isolated from various salinaria and natural hypersaline environments. These isolates (strains FDF-1T [T = type strain], FDF-2, SF-2, Ret-1, SD-1, and Cas-1) grew on media containing methanol and mono-, di-, and trimethylamines as catabolic substrates, but not on media containing dimethyl sulfide, methane thiol, H2, formate, or acetate; when cells were provided with H2 in addition to methanol or trimethylamine, they grew on the medium containing a methyl substrate but did not catabolize H2. All of the strains were capable of growth in mineral medium to which trimethylamine was added as a catabolic substrate, although some strains were greatly stimulated by biotin or p-aminobenzoate. DNA reassociation and denaturing electrophoresis of whole-cell proteins indicated that strains FDF-1T, FDF-2, SF-2, and Ret-1, together with previously described strains SF-1, Z-7302, Z-7401, Z-7401, and Z-7405, belong to a new taxon named Methanohalophilus portucalensis sp. nov; FDF-1 (= OCM 59) is the type strain. These strains grew fastest at temperatures near 40°C and, in medium containing 0.5 to 2.5 M NaCI, at pH values near 7. The two new strains excluded from the species on the basis of the results of phylogenetic tests, strains Cas-1 and SD-1, also differed from M. portucalensis in some minor physiological characteristics. Strain Cas-1 was less halophilic (fastest growth occurred in the presence of 0.5 to 1 M NaCI), and strain SD-1 was slightly alkaliphilic (fastest growth occurred at pH 7.8). The DNA reassociation study also showed that Methanohalophilus mahii SLPT exhibited 52% sequence similarity with Methanohalophilus halophilus Z-7982T, supporting the classification of these organisms as separate but closely related species.
Present address: Instituttet for Bioteknologi, Danmarks Tekniske Højskole, DK-2800 Lyngby, Denmark. This article has been cited by other articles:
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  C.-J. Shih and M.-C. Lai Analysis of the AAA+ chaperone clpB gene and stress-response expression in the halophilic methanogenic archaeon Methanohalophilus portucalensis Microbiology, August 1, 2007; 153(8): 2572 - 2583. [Abstract] [Full Text] [PDF]
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 P. J. Waldron, S. T. Petsch, A. M. Martini, and K. Nusslein Salinity Constraints on Subsurface Archaeal Diversity and Methanogenesis in Sedimentary Rock Rich in Organic Matter Appl. Envir. Microbiol., July 1, 2007; 73(13): 4171 - 4179. [Abstract] [Full Text] [PDF]
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 M.-C. Lai, T.-Y. Hong, and R. P. Gunsalus Glycine Betaine Transport in the Obligate Halophilic Archaeon Methanohalophilus portucalensis J. Bacteriol., September 1, 2000; 182(17): 5020 - 5024. [Abstract] [Full Text]
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 K. Horikoshi Alkaliphiles: Some Applications of Their Products for Biotechnology Microbiol. Mol. Biol. Rev., December 1, 1999; 63(4): 735 - 750. [Abstract] [Full Text] [PDF]
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M.-C. Lai, D.-R. Yang, and M.-J. Chuang Regulatory Factors Associated with Synthesis of the Osmolyte Glycine Betaine in the Halophilic Methanoarchaeon Methanohalophilus portucalensis Appl. Envir. Microbiol., February 1, 1999; 65(2): 828 - 833. [Abstract] [Full Text]
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