ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
A mutation in the mch gene, encoding the enzyme 5,10-methenyl tetrahydromethanopterin (H4MPT) cyclohydrolase, was constructed in vitro and recombined onto the chromosome of the methanogenic archaeon Methanosarcina barkeri. The resulting mutant does not grow in media using H2/CO2, methanol, or acetate as carbon and energy sources, but does grow in media with methanol/H2/CO2, demonstrating its ability to utilize H2 as a source of electrons for reduction of methyl groups. Cell suspension experiments showed that methanogenesis from methanol or from H2/CO2 is blocked in the mutant, explaining the lack of growth on these substrates. The corresponding mutation in Methanosarcina acetivorans C2A, which cannot grow on H2/CO2, could not be made in wild-type strains, but could be made in strains carrying a second copy of mch, suggesting that M. acetivorans is incapable of methyl group reduction using H2. M. acetivorans mch mutants could also be constructed in strains carrying the M. barkeri ech hydrogenase operon, suggesting that the block in the methyl reduction pathway is at the level of H2 oxidation. Interestingly, the ech-dependent methyl reduction pathway of M. acetivorans involves an electron transport chain distinct from that used by M. barkeri, because M. barkeri ech mutants remain capable of H2-dependent methyl reduction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.2005.04514.x
