Effects of Hydrogen Pressure during Growth and Effects of Pregrowth with Hydrogen on Acetate Degradation by Methanosarcina Species

Abstract

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