title: Microbial communities mediating algal detritus turnover under anaerobic conditions.
abstract: BACKGROUND
  Algae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored.
  
  
  RESULTS
  Here, we characterized the microbial communities mediating the degradation ofChlorella vulgaris(Chlorophyta),Charasp. strain IWP1 (Charophyceae), and kelpAscophyllum nodosum(phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O' the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13-16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genusClostridium, or familyVeillonellaceaewithin the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched included the uncultured groups VadinBC27 and WCHB1-69 within the Bacteroidetes, genusSpirochaetaand the uncultured group SHA-4 within Spirochaetes,Ruminococcaceae,Lachnospiraceae,Yongiibacter,Geosporobacter, andAcidaminobacterwithin the Firmicutes, and generaKluyvera,Pantoea,EdwardsiellaandAeromonas,andButtiauxellawithin the Gamma-Proteobaceteria order Enterobacteriales.
  
  
  CONCLUSIONS
  Our results represent the first systematic survey of microbial communities mediating turnover of algal biomass under anaerobic conditions, and highlights the diversity of lineages putatively involved in the degradation process.
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Morrison
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Chelsea L
authors.initials: CL
authors.lastname: Murphy
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Kristina
authors.initials: K
authors.lastname: Baker
authors.affiliation: Grand River Dam Authority , Vinita , OK , USA.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Zamor
authors.affiliation: Grand River Dam Authority , Vinita , OK , USA.
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Nikolai
authors.affiliation: Department of Integrative Biology, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Shawn
authors.initials: S
authors.lastname: Wilder
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Mostafa S
authors.initials: MS
authors.lastname: Elshahed
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
authors.forename: Noha H
authors.initials: NH
authors.lastname: Youssef
keywords: Algal detritus; Anaerobic degradation; Enrichment