title: Comparative analysis of taxonomic, functional, and metabolic patterns of microbiomes from 14 full-scale biogas reactors by metagenomic sequencing and radioisotopic analysis.
abstract: BACKGROUND
  Biogas production is a very complex process due to the high complexity in diversity and interactions of the microorganisms mediating it, and only limited and diffuse knowledge exists about the variation of taxonomic and functional patterns of microbiomes across different biogas reactors, and their relationships with the metabolic patterns. The present study used metagenomic sequencing and radioisotopic analysis to assess the taxonomic, functional, and metabolic patterns of microbiomes from 14 full-scale biogas reactors operated under various conditions treating either sludge or manure.
  
  
  RESULTS
  The results from metagenomic analysis showed that the dominant methanogenic pathway revealed by radioisotopic analysis was not always correlated with the taxonomic and functional compositions. It was found by radioisotopic experiments that the aceticlastic methanogenic pathway was dominant, while metagenomics analysis showed higher relative abundance of hydrogenotrophic methanogens. Principal coordinates analysis showed the sludge-based samples were clearly distinct from the manure-based samples for both taxonomic and functional patterns, and canonical correspondence analysis showed that the both temperature and free ammonia were crucial environmental variables shaping the taxonomic and functional patterns. The study further the overall patterns of functional genes were strongly correlated with overall patterns of taxonomic composition across different biogas reactors.
  
  
  CONCLUSIONS
  The discrepancy between the metabolic patterns determined by metagenomic analysis and metabolic pathways determined by radioisotopic analysis was found. Besides, a clear correlation between taxonomic and functional patterns was demonstrated for biogas reactors, and also the environmental factors that shaping both taxonomic and functional genes patterns were identified.
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, 200433 Shanghai, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Luo
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs Lyngby, Denmark.
authors.forename: Ioannis A
authors.initials: IA
authors.lastname: Fotidis
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs Lyngby, Denmark.
authors.forename: Irini
authors.initials: I
authors.lastname: Angelidaki
keywords: Biogas reactors; Functional patterns; Metagenomic sequencing; Methanogenic pathway; Taxonomic patterns