title: Analyses of spatial distributions of sulfate-reducing bacteria and their activity in aerobic wastewater biofilms.
abstract: The vertical distribution of sulfate-reducing bacteria (SRB) in aerobic wastewater biofilms grown on rotating disk reactors was investigated by fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. To correlate the vertical distribution of SRB populations with their activity, the microprofiles of O(2), H(2)S, NO(2)(-), NO(3)(-), NH(4)(+), and pH were measured with microelectrodes. In addition, a cross-evaluation of the FISH and microelectrode analyses was performed by comparing them with culture-based approaches and biogeochemical measurements. In situ hybridization revealed that a relatively high abundance of the probe SRB385-stained cells (approximately 10(9) to 10(10) cells per cm(3) of biofilm) were evenly distributed throughout the biofilm, even in the oxic surface. The probe SRB660-stained Desulfobulbus spp. were found to be numerically important members of SRB populations (approximately 10(8) to 10(9) cells per cm(3)). The result of microelectrode measurements showed that a high sulfate-reducing activity was found in a narrow anaerobic zone located about 150 to 300 microm below the biofilm surface and above which an intensive sulfide oxidation zone was found. The biogeochemical measurements showed that elemental sulfur (S(0)) was an important intermediate of the sulfide reoxidation in such thin wastewater biofilms (approximately 1,500 microm), which accounted for about 75% of the total S pool in the biofilm. The contribution of an internal Fe-sulfur cycle to the overall sulfur cycle in aerobic wastewater biofilms was insignificant (less than 1%) due to the relatively high sulfate reduction rate.
authors.affiliation: Department of Urban and Environmental Engineering, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-0813, Japan. sokabe@eng.hokudai.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Okabe
authors.forename: T
authors.initials: T
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Satoh
authors.forename: Y
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000332:Aerobiosis; D018441:Biofilms; D003901:Desulfovibrio / Q000145:classification / Q000302:isolation & purification; D004563:Electrochemistry / Q000379:methods; D008839:Microelectrodes; D015345:Oligonucleotide Probes; D010084:Oxidation-Reduction; D020560:Proteobacteria / Q000145:classification* / Q000235:genetics / Q000502:physiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000145:classification* / Q000235:genetics / Q000502:physiology
chemical_list: D015345:Oligonucleotide Probes; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D013431:Sulfates