title: Effects of heat shocks on microbial community structure and microbial activity of a methanogenic enrichment degrading benzoate.
abstract: In anaerobic digesters, temperature fluctuation could lead to process instability and failure. It is still not well understood how digester microbiota as a whole respond to heat shock, and what specific organisms are vulnerable to perturbation or responsible for process recovery after perturbation. To address these questions, a mesophilic benzoate-degrading methanogenic culture enriched from digester was subjected to different levels of heat shock. Three types of methane production profiles after perturbation were observed in comparison to the control: uninhibited, inhibited with later recovery, and inhibited without recovery. These responses were correlated with the microbial community compositions based on the analyses of 16S rRNA and 16S rRNA gene. Specifically, the primary benzoate-degrading syntroph was highly affected by heat shock, and its abundance and activity were both crucial to the restoration of benzoate degradation after heat shock. In contrast, methanogens were stable regardless whether methane production was inhibited. Populations related to 'Candidatus Cloacimonetes' and Firmicutes showed stimulated growth. These observations indicated distinct physiological traits and ecological niches associated with individual microbial groups. The results obtained after exposure to heat shock can be critical to more comprehensive characterization of digester ecology under perturbations.
  
  
  CONCLUSIONS
  Anaerobic digestion is an essential step in municipal wastewater treatment owing to its striking capacity of reducing wasted sludge and recovering energy. However, as an elaborate microbial process, it requires constant temperature control and is sensitive to heat shock. In this study, we explored the microbial response to heat shock of a methanogenic culture enriched from anaerobic digester sludge. Microorganisms that were vulnerable to perturbation or responsible for process recovery after perturbation were identified.
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: R
authors.initials: R
authors.lastname: Mei
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.|Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Narihiro
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Nobu
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA. wtliu@illinois.edu.
authors.forename: W-T
authors.initials: WT
authors.lastname: Liu
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D001565:Benzoates / Q000378:metabolism*; D019149:Bioreactors; D019605:Euryarchaeota / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000068536:Bacillota / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D006358:Hot Temperature; D008697:Methane / Q000096:biosynthesis*; D020560:Proteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D018508:Water Purification / Q000379:methods
chemical_list: D001565:Benzoates; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D008697:Methane
keywords: 16S rRNA; 16S rRNA gene; anaerobic digestion; heat shock; high-throughput sequencing; methane production; microbial community structure