@article{mbs:/content/journal/micro/10.1099/00221287-128-1-1, author = "Jones, J. Gwynfryn and Simon, Bernard M. and Gardener, Steven", title = "Factors Affecting Methanogenesis and Associated Anaerobic Processes in the Sediments of a Stratified Eutrophic Lake", journal= "Microbiology", year = "1982", volume = "128", number = "1", pages = "1-11", doi = "https://doi.org/10.1099/00221287-128-1-1", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-128-1-1", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "Factors affecting methanogenesis in the sediments of a eutrophic lake were studied during late summer, a period during which CH4 gas production slowed down dramatically or stopped completely. The most active methanogenesis occurred in the surface sediments and the temperature optimum for the process in these deeper sediments was 30 °C. Addition of H2 or formic acid to sediment slurries stimulated CH4 production to a greater extent than did acetic or pyruvic acid. Analysis of the kinetics of the conversion of H2 to CH4 suggested that the sediments were severely limited in H2, the concentration being considerably less than 2·5 μmol 1−1, the Km for the process. Methanogenesis was not stimulated by the addition of trace quantities of Ni2+, Co2+, MoO4 2− or Fe2+ ions but was inhibited by 0·5 mmol SO4 2− 1−1. Under natural conditions the sediments were also limited in SO4 2− and sulphate reducers acted as net H2 donors to the methanogens; addition of SO4 2− allowed the sulphate reducers to compete effectively for H2. The addition of 20 mmol Na2MoO4 1−1 to sediments inhibited methanogenesis but this was not due entirely to its effect in the H2 transfer from sulphate reducers; it also inhibited CO2 uptake by sediments and the production of CH4 from CH3COOH and CO2 by cultures of methanogens. It is therefore inadvisable to use MoO4 2− at this concentration as a specific inhibitor of sulphate reducers in such freshwater sediments. Experiments with other inhibitors of methanogens suggested that they may interact with sulphate reducers, acetogens or anaerobic bacteria involved in fatty acid decomposition. Small, sealed sediment cores, which were used to reproduce natural conditions, particularly of available H2 concentration, were injected with trace quantities of H14CO3 − and 14CH3COOH. The results suggested that more than 75% of the CH4 was derived from CO2 and the remainder from CH3COOH. The overall rates of methanogenesis in the small cores agreed well with results from the field.", }