title: Pyrosequencing analysis yields comprehensive assessment of microbial communities in pilot-scale two-stage membrane biofilm reactors.
abstract: We studied the microbial community structure of pilot two-stage membrane biofilm reactors (MBfRs) designed to reduce nitrate (NO3(-)) and perchlorate (ClO4(-)) in contaminated groundwater. The groundwater also contained oxygen (O2) and sulfate (SO4(2-)), which became important electron sinks that affected the NO3(-) and ClO4(-) removal rates. Using pyrosequencing, we elucidated how important phylotypes of each "primary" microbial group, i.e., denitrifying bacteria (DB), perchlorate-reducing bacteria (PRB), and sulfate-reducing bacteria (SRB), responded to changes in electron-acceptor loading. UniFrac, principal coordinate analysis (PCoA), and diversity analyses documented that the microbial community of biofilms sampled when the MBfRs had a high acceptor loading were phylogenetically distant from and less diverse than the microbial community of biofilm samples with lower acceptor loadings. Diminished acceptor loading led to SO4(2-) reduction in the lag MBfR, which allowed Desulfovibrionales (an SRB) and Thiothrichales (sulfur-oxidizers) to thrive through S cycling. As a result of this cooperative relationship, they competed effectively with DB/PRB phylotypes such as Xanthomonadales and Rhodobacterales. Thus, pyrosequencing illustrated that while DB, PRB, and SRB responded predictably to changes in acceptor loading, a decrease in total acceptor loading led to important shifts within the "primary" groups, the onset of other members (e.g., Thiothrichales), and overall greater diversity.
authors.affiliation: Biodesign Institute, Swette Center for Environmental Biotechnology, Arizona State University , 1001 South McAllister Avenue, Tempe, Arizona 85287-5701, United States.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
authors.forename: David
authors.initials: D
authors.lastname: Friese
authors.forename: Ryan
authors.initials: R
authors.lastname: Overstreet
authors.forename: Jennifer
authors.initials: J
authors.lastname: Smith
authors.forename: Patrick
authors.initials: P
authors.lastname: Evans
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics*; D018441:Biofilms; D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D008567:Membranes, Artificial; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000378:metabolism; D010802:Phylogeny; D010865:Pilot Projects; D025341:Principal Component Analysis; D017422:Sequence Analysis, DNA / Q000379:methods*; D013431:Sulfates / Q000378:metabolism; D013997:Time Factors
chemical_list: D008567:Membranes, Artificial; D009566:Nitrates; D010472:Perchlorates; D013431:Sulfates; D006859:Hydrogen; C494474:perchlorate