Effects of hydrogen pressure during growth and effects of pregrowth with hydrogen on acetate degradation by Methanosarcina species. [Methanosarcina barkeri; Methanosarcina mazei]

Methanosarcina barkeri 227 and Methanosarcina mazei S-6 grew with acetate as the substrate; little effect of H/sub 2/ on the rate of aceticlastic growth was found in the presence of various H/sub 2/ pressures between 2 and 810 Pa. Physical (H/sub 2/ addition or flushing the headspace to remove H/sub 2/) and biological (H/sub 2/-producing or -utilizing bacteria in cocultures) methods were used for controlling H/sub 2/ pressure in Methanosarcina cultures growing on acetate. Added H/sub 2/ (ca. 100 Pa) was removed rapidly (a few hours) by M. barkeri and slowly (within a day) by M. mazei. When the H/sub 2/ produced by the aceticlastic methanogens was removed by coculturing with an H/sub 2/-using Desulfovibrio sp., the H/sub 2/ pressure was about 2.2 Pa. Under these conditions the stoichiometry of aceticlastic methanogenesis did not change. H/sub 2/-grown inocula of M. barkeri grew with acetate as the sole catabolic substrate if the inoculum culture was transferred during logarithmic growth to acetate-containing medium or if the transfer was accomplished with 1 or 2 days after exhaustion of H/sub 2/. H/sub 2/-grown cultures incubated for 4 or more days after exhaustion of H/sub 2/ were able to grow with H/sub 2/ but notmore » with acetate as the sole catabolic substrate. Addition of small quantities of H/sub 2/ to acetate-containing medium permitted these cultures to initiate growth on acetate.« less