title: Nitrate stimulation of indigenous nitrate-reducing, sulfide-oxidising bacterial community in wastewater anaerobic biofilms.
abstract: The role of the nitrate-reducing, sulfide-oxidising bacteria (NR-SOB) in the nitrate-mediated inhibition of sulfide net production by anaerobic wastewater biofilms was analyzed in two experimental bioreactors, continuously fed with the primary effluent of a wastewater treatment plant, one used as control (BRC) and the other one supplemented with nitrate (BRN). This study integrated information from H(2)S and pH microelectrodes, RNA-based molecular techniques, and the time course of biofilm growth and bioreactors water phase. Biofilms were a net source of sulfide for the water phase (2.01 micromol S(2-)(tot)m(-2)s(-1)) in the absence of nitrate dosing. Nitrate addition effectively led to the cessation of sulfide release from biofilms despite which a low rate of net sulfate reduction activity (0.26 micromol S(2-)(tot)m(-2)s(-1)) persisted at a deep layer within the biofilm. Indigenous NR-SOB including Thiomicrospira denitrificans, Arcobacter sp., and Thiobacillus denitrificans were stimulated by nitrate addition resulting in the elimination of most sulfide from the biofilms. Active sulfate reducing bacteria (SRB) represented comparable fractions of total metabolically active bacteria in the libraries obtained from BRN and BRC. However, we detected changes in the taxonomic composition of the SRB community suggesting its adaptation to a higher level of NR-SOB activity in the presence of nitrate.
authors.affiliation: Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, Pol. Río San Pedro s/n, 11510 Puerto Real, Cadiz, Spain. juan.garciadelomas@uca.es
authors.forename: Juan
authors.initials: J
authors.lastname: Garcia-de-Lomas
authors.forename: Alfonso
authors.initials: A
authors.lastname: Corzo
authors.forename: M
authors.initials: M
authors.lastname: Carmen Portillo
authors.forename: Juan M
authors.initials: JM
authors.lastname: Gonzalez
authors.forename: Jose A
authors.initials: JA
authors.lastname: Andrades
authors.forename: Cesáreo
authors.initials: C
authors.lastname: Saiz-Jimenez
authors.forename: Emilio
authors.initials: E
authors.lastname: Garcia-Robledo
mesh_terms: D000693:Anaerobiosis / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D018533:Biomass; D019149:Bioreactors; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D013440:Sulfides / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000187:drug effects / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods*; D014871:Water Microbiology
chemical_list: D009566:Nitrates; D013440:Sulfides