Composition of the archaeal community involved in methane production during the decomposition of Microcystis blooms in the laboratory.

We investigated the microbial processes involved in methane (CH(4)) production from Microcystis bloom scums at different temperatures. A Microcystis slurry was collected from Lake Taihu and incubated in airtight bottles at 15, 25, and 35 °C. The production of CH(4) was monitored, and the emission rate was calculated. The dynamics of the methanogenic community were analyzed by terminal restriction fragment length polymorphism analysis of archaeal 16S rRNA genes. Phylogenetic information for the methanogens was obtained by cloning and sequencing selected samples. Significant CH(4) emission from the Microcystis scums was delayed by approximately 12 days by the natural oxygen depletion process, and CH(4) production was enhanced at higher temperatures. Phylogenetic analysis indicated that the archaeal community was composed of Methanomicrobiales, Methanobacteriaceae, and a novel cluster of Archaea. An apparent succession of the methanogenic community was demonstrated, with a predominance of Methanobacteriaceae at higher temperatures. Higher temperatures enhanced the methanogenic transformation of the Microcystis biomass and the phylogenetic dominance of hydrogenotrophic methanogens, suggesting that H(2) and CO(2) might be the primary substrates for CH(4) production during Microcystis decomposition without the participation of lake sediment. This work provides insight into the microbial components involved in Microcystis biomass fermentation in controlled systems.