title: Reorganization of the bacterial and archaeal populations associated with organic loading conditions in a thermophilic anaerobic digester.
abstract: Organic loading conditions are an important factor influencing reactor performances in methanogenic bioreactors. Yet the underlying microbiological basis of the process stability, deterioration, and recovery remains to be understood. Here, structural responses of the bacterial and archaeal populations to the change of organic loading conditions in a thermophilic anaerobic digester were investigated by process analyses and 16S rRNA gene-based molecular approaches. The biogas was produced stably without the accumulation of volatile fatty acids (VFAs) at low organic loading rates (OLRs) in the beginning of reactor operation. Increasing OLR in stages disrupted the stable reactor performance, and high OLR conditions continued the deteriorated performance with slight biogas production and high accumulation of VFAs. Thereafter, the gradual decrease of OLR resulted in the recovery from the deterioration, giving rise to the stable performance again. The stable performances before and after the high OLR conditions conducted were associated with compositionally similar but not identical methanogenic consortia. The bacterial and archaeal populations were synchronously changed at both the transient phases toward the deteriorated performance and in recovery process, during which the dynamic shift of aceticlastic and hydrogenotrophic methanogens including the recently identified Methanomassiliicoccus might contribute to the maintenance of the methanogenic activity. The distinctive bacterial population with a high predominance of Methanobacterium formicicum as archaeal member was found for the deteriorated performance. The results in this study indicate the coordinated reorganization of the bacterial and archaeal populations in response to functional states induced by the change of organic loading conditions in the anaerobic digester.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan. Electronic address: hori-tomo@aist.go.jp.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hori
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Haruta
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 675-8501, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sasaki
authors.affiliation: Dairy Research Division, National Agricultural Research Center for Hokkaido Region, National Agricultural and Food Research Organization, 1 Hitsujigaoka, Sapporo 062-8555, Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Hanajima
authors.affiliation: Kajima Technical Research Institute, 2-19-1 Tobitakyu, Chofu-shi, Tokyo 182-0036, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ueno
authors.affiliation: Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ogata
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Research Center of Bioenergy and Bioremediation, Southwest University, BeiBei District, Chongqing 400715, China.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D056804:Biofuels / Q000032:analysis; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D005232:Fatty Acids, Volatile; D008697:Methane / Q000378:metabolism; D017014:Methanobacterium / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D056804:Biofuels; D005232:Fatty Acids, Volatile; D012336:RNA, Ribosomal, 16S; D008697:Methane
keywords: 16S rRNA gene-based molecular approach; Anaerobic digester; Methanogenic population; Organic loading condition; Reorganization