Characterization of Methanosarcina barkeri MST and 227, Methanosarcina mazei S-6T, and Methanosarcina vacuolata Z-761T

Abstract

Members of the genus Methanosarcina are recognized as major aceticlastic methanogens, and several species which thrive in low-salt, pH-neutral culture medium at mesophilic temperatures have been described. However, the environmental conditions which support the fastest growth of these species (Methanosarcina barkeri MST [T = type strain] and 227, Methanosarcina mazei S-6T, and Methanosarcina vacuolata Z-761T) have not been reported previously. Although the members of the genus Methanosarcina are widely assumed to grow best at pH values near neutrality, we found that some strains prefer acidic pH values. M. vacuolata and the two strains of M. barkeri which we tested were acidophilic when they were grown on H, plus methanol, growing most rapidly at pH 5 and growing at pH values as low as 4.3. M. mazei grew best at pH values near neutrality. We found that all of the strains tested grew most rapidly at 37 to 42°C on all of the growth substrates which we tested. None of the strains was strongly halophilic, although the growth of some strains was slightly stimulated by small amounts of added NaCI. The catabolic substrates which supported most rapid growth were H, plus methanol; this combination sometimes allowed growth of a strain under extreme environmental conditions which prevented growth on other substrates. The cell morphology of all strains was affected by growth conditions.Although Methanosarcina species have been the subjects of extensive metabolic studies, other aspects of the characterization of these organisms do not meet even the minimal standards for description of methanogenic taxa (9). In this study we examined the physiology of the following three mesophilic, aceticlastic species: Methanosarcina barkeri, Methanosarcina mazei, and Methanosarcina vacuolata. Methanosarcina acetivorans, the only other mesophilic and aceticlastic Methanosarcina species, was not included in this study because it has been well characterized (35).The original type strain of M. barkeri, isolated by C. G. T. P. Schnellen (32a), has been lost. In 1966, Bryant isolated strain MS (lo), which has been adopted as the type strain (4). Although this strain is one of the most extensively studied methanogens, previous studies have not included definitive determinations of its responses to environmental conditions such as pH, temperature, and salinity. Strain 227 (25) is another extensively studied strain which DNA hybridization studies (37) indicate is a member of M. barkeri. Methanogenic cocci were first described by Groenewege (12) in 1920 and were later observed by Kluyver and van Niel (17). These cocci were physiologically similar to M . barkeri, but because of morphological differences between the cocci and M . barkeri, Kluyver and van Niel proposed a new genus (Methanococcus) for the cocci. Later Barker (6) studied a purified, nonaxenic culture and named it Methanococcus mazei. Pure cultures of this species were not available until more than 40 years later. Zhilina and Zavarzin (44) also studied an aceticlastic enrichment culture w...

Monitoring of the microbial community composition in saline aquifers during CO2 storage by fluorescence in situ hybridisation

“…Methanogenic archaea are highly resistant microorganisms that may use only hydrogen and CO 2 as energy and carbon sources and do not require other organic substrates. Interestingly, certain strains of methanogenic archaea have been shown to grow at low pH (Maestrojuan and Boone, 1991). Furthermore, resent studies revealed shifts in methanogenic community to the H 2 -dependent methanogenesis at low pH (Kotsyurbenko et al, 2007).…”

Isolation and Characterization of Methanohalophilus portucalensis sp. nov. and DNA Reassociation Study of the Genus Methanohalophilus

“…Members of the genus Methanohalophilus are moderately halophilic, growing fastest in the presence of 0.5 to 2.5 M NaCl (23), and members of the genus Methanohalobium are extremely halophilic, growing fastest in the presence of NaCl concentrations greater than 2 M (36). No genus other than these four contains halophilic met hylotrophic met hanogens; although several halophiles were reported in the closely related genus Methanosarcina (2,28), other studies indicated that these species are halotolerant rather than halophilic (12,13). The genus Halomethanococcus has also been proposed (33), but we do not include it in our taxonomy because we have been unable to obtain the type strain of the only species described in this genus (Halomethanococcus doii) and because the name Halomethanococcus may be a subjective synonym of Methanohalophilus.…”

“…Methane was quantified by gas chromatographic analysis of samples collected at the pressure of the vessels, thereby giving values for amount of methane per volume of headspace rather than per volume of gas under standard conditions. Samples were collected in pressure lock syringes and were detected by thermal conductivity (1) or by a sampling loop with flame ionization detection (12). Specific growth rates were calculated by least-squares analysis of the rate of increase of the logarithm of accumulated methane level.…”

Isolation and characterization of a new Methanosarcina mazei strain GFJ07 from a mountain forest pond

“…Although it was reported that M. barkeri, M. mazei, and M. vacuolata could be distinguished from other methanogens by the characteristics that they can produce ISSN (print): 1823-8262, ISSN (online): 2231 methane from trimethylamine, methanol, H2-CO2 and acetate (Maestrojuan and Boone, 1991), It was found later that strains of M. mazei could not metabolize H2-CO2 (Cairó et al, 1992;Clarens et al, 1993). Thus, the standard for using H2-CO2 to distinguish M. mazei from other species is inaccurate.…”

“…Specific growth rate was calculated from the methane production curves during exponential phase (Maestrojuan and Boone, 1991) and three parallel cultures were analyzed. Methane production were determined by gas chromatogragh (Techcomp GC7890II) equipped with a thermal conductivity detector and GDX-502 column.…”