Premium
Genetic analysis of mch mutants in two Methanosarcina species demonstrates multiple roles for the methanopterin‐dependent C‐1 oxidation/reduction pathway and differences in H 2 metabolism between closely related species
Author(s) -
Guss Adam M.,
Mukhopadhyay Biswarup,
Zhang Jun Kai,
Metcalf William W.
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04514.x
Subject(s) - methanosarcina barkeri , methanosarcina , methanomicrobiales , biology , mutant , operon , biochemistry , hydrogenase , methanogenesis , methanol , microbiology and biotechnology , gene , enzyme , archaea , genetics , bacteria , chemistry , organic chemistry
Summary A mutation in the mch gene, encoding the enzyme 5,10‐methenyl tetrahydromethanopterin (H 4 MPT) 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 H 2 /CO 2 , methanol, or acetate as carbon and energy sources, but does grow in media with methanol/H 2 /CO 2 , demonstrating its ability to utilize H 2 as a source of electrons for reduction of methyl groups. Cell suspension experiments showed that methanogenesis from methanol or from H 2 /CO 2 is blocked in the mutant, explaining the lack of growth on these substrates. The corresponding mutation in Methanosarcina acetivorans C2A, which cannot grow on H 2 /CO 2 , 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 H 2 . 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 H 2 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 H 2 ‐dependent methyl reduction.