title: Effects of multiple electron acceptors on microbial interactions in a hydrogen-based biofilm.
abstract: To investigate interactions among multiple electron acceptors in a H2-fed biofilm, we operated a membrane biofilm reactor with H2-delivery capacity sufficient to reduce all acceptors. ClO4(-) and O2 were input electron acceptors in all stages at surface loadings of 0.08 ± 0.006 g/m(2)-d (1.0 ± 0.7 e(-) meq/m(2)-d) for ClO4(-) and 0.51 g/m(2)-d (76 e(-) meq/m(2)-d) for O2. SO4(2-) was added in Stage 2 at 3.77 ± 0.39 g/m(2)-d (331 ± 34 e(-) meq/m(2)-d), and NO3(-) was further added in Stage 3 at 0.72 ± 0.03 g N/m(2)-d (312 ± 13 e(-) meq/m(2)-d). At steady state for each stage, ClO4(-), O2, and NO3(-) (when present in the influent) were completely reduced; measured SO4(2-) reduction decreased from 78 ± 4% in Stage 2 to 59 ± 4% in Stage 3, when NO3(-) was present. While perchlorate-reducing bacteria (PRB), assayed by qPCR targeting the pcrA gene, remained stable throughout, sulfate-reducing bacteria (SRB), assayed by the dsrA gene, increased almost 3 orders of magnitude when significant SO4(2-) reduction occurred in stage 2. The abundance of denitrifying bacteria (DB), assayed by the nirK and nirS genes, increased in Stage 3, while SRB remained at high numbers, but did not increase. Based on pyrosequencing analyses, β-Proteobacteria dominated in Stage 1, but ε-Proteobacteria became more important in Stages 2 and 3, when the input of multiple electron acceptors favored genera with broader electron-accepting capabilities. Sulfuricurvum (a sulfur oxidizer and NO3(-) reducer) and Desulfovibrio (a SO4(2-) reducer) become dominant in Stage 3, suggesting redox cycling of sulfur in the biofilm.
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, Arizona 85287-5701, United States.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
authors.forename: Zehra Esra
authors.initials: ZE
authors.lastname: Ilhan
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
mesh_terms: D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms; D019149:Bioreactors; D004269:DNA, Bacterial / Q000235:genetics; D006859:Hydrogen / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010472:Perchlorates / Q000737:chemistry; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013431:Sulfates / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D009566:Nitrates; D010472:Perchlorates; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D006859:Hydrogen; D010100:Oxygen; C494474:perchlorate