title: Identification and genome reconstruction of abundant distinct taxa in microbiomes from one thermophilic and three mesophilic production-scale biogas plants.
abstract: BACKGROUND
  Biofuel production from conversion of biomass is indispensable in the portfolio of renewable energies. Complex microbial communities are involved in the anaerobic digestion process of plant material, agricultural residual products and food wastes. Analysis of the genetic potential and microbiology of communities degrading biomass to biofuels is considered to be the key to develop process optimisation strategies. Hence, due to the still incomplete taxonomic and functional characterisation of corresponding communities, new and unknown species are of special interest.
  
  
  RESULTS
  Three mesophilic and one thermophilic production-scale biogas plants (BGPs) were taxonomically profiled using high-throughput 16S rRNA gene amplicon sequencing. All BGPs shared a core microbiome with the thermophilic BGP featuring the lowest diversity. However, the phyla Cloacimonetes and Spirochaetes were unique to BGPs 2 and 3, Fusobacteria were only found in BGP3 and members of the phylum Thermotogae were present only in the thermophilic BGP4. Taxonomic analyses revealed that these distinctive taxa mostly represent so far unknown species. The only exception is the dominant Thermotogae OTU featuring 16S rRNA gene sequence identity to Defluviitoga tunisiensis L3, a sequenced and characterised strain. To further investigate the genetic potential of the biogas communities, corresponding metagenomes were sequenced in a deepness of 347.5 Gbp in total. A combined assembly comprised 80.3 % of all reads and resulted in the prediction of 1.59 million genes on assembled contigs. Genome binning yielded genome bins comprising the prevalent distinctive phyla Cloacimonetes, Spirochaetes, Fusobacteria and Thermotogae. Comparative genome analyses between the most dominant Thermotogae bin and the very closely related Defluviitoga tunisiensis L3 genome originating from the same BGP revealed high genetic similarity. This finding confirmed applicability and reliability of the binning approach. The four highly covered genome bins of the other three distinct phyla showed low or very low genetic similarities to their closest phylogenetic relatives, and therefore indicated their novelty.
  
  
  CONCLUSIONS
  In this study, the 16S rRNA gene sequencing approach and a combined metagenome assembly and binning approach were used for the first time on different production-scale biogas plants and revealed insights into the genetic potential and functional role of so far unknown species.
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Stolze
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.|Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bremges
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.|Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Madis
authors.initials: M
authors.lastname: Rumming
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.|Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Henke
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Irena
authors.initials: I
authors.lastname: Maus
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Alfred
authors.initials: A
authors.lastname: Pühler
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.|Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Sczyrba
authors.affiliation: Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schlüter
keywords: 16S rRNA gene; Anaerobic digestion; Biogas; Cloacimonetes (WWE1); Fusobacteria; Genome binning; Metagenomics; Microbial community; Spirochaetes; Thermotogae