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The identification of dominant microbes in anaerobic mercury (Hg) methylation, methylmercury (MeHg) demethylation, and methane oxidation as sulfate-reducing bacteria, methanogens or, probably, anaerobic methanotrophic archaea (ANMEs) is of great interest. To date, however, the interrelationship of bacteria and archaea involved in these processes remains unclear. Here, we demonstrated the dynamics of microorganisms participating in these processes. Anaerobic fixed-bed reactors were operated with swine manure and sludge to produce methane stably, and then, sulfate (reactor C), sulfate and Hg(II) (reactor H), and sulfate and MeHg (reactor M) were added, and the reactors were operated for 120 d, divided equally into four periods, P1–P4. The bacterial compositions changed nonsignificantly, whereas Methanosaeta in reactors H and M decreased significantly, revealing that it was irrelevant for Hg transformation. The abundances of Syntrophomonadaceae , Methanoculleus , Candidatus Methanogranum and Candidatus Methanoplasma increased continuously with time; these species probably functioned in these processes, but further evidence is needed. Desulfocella and Desulfobacterium dominated first but eventually almost vanished, while the dominant archaeal genera Methanogenium , Methanoculleus and Methanocorpusculum were closely related to ANME–1 and ANME–2. PLS-DA results indicated that both bacteria and archaea in different periods in the three reactors were clustered separately, implying that the microbial compositions in the same periods were similar and changed markedly with time. [Display omitted] • Methanosaeta decreased significantly after adding Hg and was unrelated to Hg transformation. • Desulfocella and Desulfobacterium dominated first but finally almost vanished. • The dominant archaeal genera were closely related to ANME–1 and ANME–2. • Microbes in different periods clustered separately, showing a significant change with time. [ABSTRACT FROM AUTHOR]

To strengthen mass heat transfer in dry fermentation and avoid the high shear forces breaking microbial flora. A reactor is designed to rotate itself instead of mechanical stirring. Its performance was verified by comparing it with the common stirring of dry digestion and wet digestion. The results showed that the designed reactor could effectively overcome the existing problems of stirring dry digestion. The total solids removal rate was up to 68.74%, which was 18% higher than that of wet digestion. Acetic acid and propionic acid were the main volatile fatty acids in dry digestion, and acetic acid and butyric acid were higher in wet digestion. The high diversity of fermentation bacteria integrated with hydrotrophic methanogens in the designed dry reactor resulted in its better performance. The information provided will be useful to research the anaerobic treatment of solid municipal waste. • A reactor used rotating instead of stirring was designed for dry fermentation. • The designed reactor performed well in the dry fermentation of kitchen waste. • More functional bacteria and hydrotrophic methanogens lead to good fermentation. • Methahnosarcina dominated in both designed dry reactor and common wet reactor. • Proteiniphilum and Enterococcus dominated in the designed reactor. [ABSTRACT FROM AUTHOR]