MEDIUM-REDUCTANT DIRECTED EXPRESSION OF METHYL COENZYME-M REDUCTASE ISOENZYMES IN METHANOBACTERIUM-THERMOAUTOTROPHICUM (STRAIN DELTA-H)

Methanobacterium thermoautotrophicum was grown in a chemostat under va rious controlled conditions in the presence of either sodium sulfide o r sodium thiosulfate. After establishment of the steady state, cells w ere taken and examined for expression of the mRNA transcripts coding f or the different forms of methyl coenzyme M reductase (MCR) and methyl ene tetrahydomethanopterin dehydrogenase (MDH). MCR isoenzyme II expre ssion varied most markedly. Expression was found not only to depend on known parameters temperature, pH and gassing rate, but also on the me dium composition, especially the reductant present. (C) 1997 Federatio n of European Biochemical Societies.