title: Interactions between nitrate-reducing and sulfate-reducing bacteria coexisting in a hydrogen-fed biofilm.
abstract: To explore the relationships between denitrifying bacteria (DB) and sulfate-reducing bacteria (SRB) in H(2)-fed biofilms, we used two H(2)-based membrane biofilm reactors (MBfRs) with or without restrictions on H(2) availability. DB and SRB compete for H(2) and space in the biofilm, and sulfate (SO(4)(2-)) reduction should be out-competed when H(2) is limiting inside the biofilm. With H(2) availability restricted, nitrate (NO(3)(-)) reduction was proportional to the H(2) pressure and was complete at a H(2) pressure of 3 atm; SO(4)(2-) reduction began at H(2) ≥ 3.4 atm. Without restriction on H(2) availability, NO(3)(-) was the preferred electron acceptor, and SO(4)(2-) was reduced only when the NO(3)(-) surface loading was ≤ 0.13 g N/m(2)-day. We assayed DB and SRB by quantitative polymerase chain reaction targeting the nitrite reductases and dissimilatory sulfite reductase, respectively. Whereas DB and SRB increased with higher H(2) pressures when H(2) availability was limiting, SRB did not decline with higher NO(3)(-) removal flux when H(2) availability was not limiting, even when SO(4)(2-) reduction was absent. The SRB trend reflects that the SRB's metabolic diversity allowed them to remain in the biofilm whether or not they were reducing SO(4)(2-). In all scenarios tested, the SRB were able to initiate strong SO(4)(2-) reduction only when competition for H(2) inside the biofilm was relieved by nearly complete removal of NO(3)(-).
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, 1001 South McAllister Ave. Tempe, AZ, USA.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Michal
authors.initials: M
authors.lastname: Ziv-El
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
authors.forename: Liang
authors.initials: L
authors.lastname: Feng
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification; D006859:Hydrogen / Q000378:metabolism; D056265:Microbial Interactions; D009566:Nitrates / Q000032:analysis / Q000378:metabolism*; D010802:Phylogeny; D013431:Sulfates / Q000032:analysis / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D009566:Nitrates; D013431:Sulfates; D014874:Water Pollutants, Chemical; D006859:Hydrogen