title: Phylogenetic analysis of nitrate- and sulfate-reducing bacteria in a hydrogen-fed biofilm.
abstract: Using two membrane biofilm reactors in which hydrogen (H₂) was the only exogenous electron donor, we studied the microbial community structure of biofilms composed primarily of denitrifying bacteria (DB) and sulfate-reducing bacteria (SRB). In steady-state EDvSS, H₂ availability was restricted and varied. In steady-state EAvSS, the input nitrate (NO₃⁻) concentration was varied relative to a fixed sulfate (SO₄²⁻) concentration. SRB co-existed with DB, even when SO₄²⁻ reduction was absent due to restricted H₂ availability. UniFrac and principal coordinate analysis indicated that H₂ availability and electron-acceptor loadings framed the microbial community structure, with H₂ availability having a greater impact. In EDvSS, restricted H₂ availability favored heterotrophic DB (i.e. Burkholderiales) compared with autotrophic DB (e.g. Hydrogenophilales and Rhodocyclales). In EAvSS, SO₄²⁻ reduction lowered the relative abundance of some DB (e.g. Hydrogenophilales), and the biofilm was colonized by Desulfovibrionales and Bacteroidales. Reinforcing the impact of H₂ availability, EAvSS showed a higher microbial diversity and more even distribution among microbial groups than did EDvSS. Thus, the biofilm community in a H₂-fed biofilm with DB and SRB became more heterotrophic when the H₂ availability was constrained, while low NO₃⁻ loading allowed more SO₄²⁻ reduction, causing a shift to more SRB.
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, Tempe, AZ 85287-5701, USA.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Zehra Esra
authors.initials: ZE
authors.lastname: Ilhan
authors.forename: Dae-Wook
authors.initials: DW
authors.lastname: Kang
authors.forename: Bruce
authors.initials: B
authors.lastname: Rittmann
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
mesh_terms: D052818:Autotrophic Processes; D001419:Bacteria / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism*; D018441:Biofilms; D058440:Denitrification; D052836:Heterotrophic Processes; D006859:Hydrogen / Q000378:metabolism*; D056265:Microbial Interactions; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D013431:Sulfates / Q000378:metabolism*
chemical_list: D009566:Nitrates; D013431:Sulfates; D006859:Hydrogen