Abstract 1403 Metabolic response to light-induced stress in methane-producing microorganisms

Sunlight benefits the development of life on Earth; however, sunlight can also have harmful effects in microorganisms such as disruption of biomolecules, mutations, and cell death. Methane-producing microorganisms, also known as methanogens or methanogenic archaea, are light-sensitive microorganisms from the Domain Archaea that generate around one billion tons of methane each year in oxygen-free environments. Sunlight inhibits the growth of methanogens in laboratory cultures, bioreactors, and natural environments, but the molecular mechanisms are unclear. We cultivated Methanosarcina acetivorans, a model methanogen isolated from coastal sediments, in oxygen-free conditions and under constant light exposure. We incubated cell cultures for 4 weeks in three light intensities (high-light, low-light, and no light) and two temperatures (22 and 28 degrees Celsius). Cell growth was determined following biomass and methane production. Our results suggest that Methanosarcina acetivorans is sensitive to blue or near-ultraviolet light and the response involves a series of changes in central and energy metabolism. When M. acetivorans was cultured at mesophilic temperature (22 degrees Celsius), constant exposure to low light and high light decreased drastically the total production of biomass and methane, compared to cells cultured in dark conditions (no light). Light exposure also changed the expression of some putative genes encoding proteins involved in the direct response to light-induced stress, but also in carbon fixation and anabolic pathways. These results contribute to our understanding of the mechanisms of energy conservation and carbon assimilation in methanogens under environmental stress conditions, and have potential applications in biotechnology and astrobiology. This work was supported by UConn MCB StartUp funds and Scholarship Facilitation Fund (SFF #4656550) Award from UConn Office of the Vice President for Research, as well as the UConn Chapter of the Ronald E. McNair Scholars Federal TRIO program.