title: In situ detection of protein-hydrolysing microorganisms in activated sludge.
abstract: Protein hydrolysis plays an important role in the transformation of organic matter in activated sludge wastewater treatment plants, but no information is currently available regarding the identity and ecophysiology of protein-hydrolysing organisms (PHOs). In this study, fluorescence in situ enzyme staining with casein and bovine serum albumin conjugated with BODIPY dye was applied and optimized to label PHOs in activated sludge plants. A strong fluorescent labeling of the surface of microorganisms expressing protease activity was achieved. Metabolic inhibitors were applied to inhibit the metabolic activity to prevent uptake of the fluorescent hydrolysates by oligopeptide-consuming bacteria. In five full-scale, nutrient-removing activated sludge plants examined, the dominant PHOs were always different morphotypes of filamentous bacteria and the epiflora attached to many of these. The PHOs were identified by FISH using a range of available oligonucleotide probes. The filamentous PHOs belonged to the candidate phylum TM7, the phylum Chloroflexi and the class Betaproteobacteria. In total they comprised 1-5% of the bacterial biovolume. Most of the epiflora-PHOs hybridized with probe SAP-309 targeting Saprospiraceae in the phylum Bacteroidetes and accounted for 8-12% of the total bacterial biovolume in most plants and were thus an important and dominant part of the microbial communities.
authors.affiliation: Department of Biotechnology, Chemistry and Environmental Engineering, Section of Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark.
authors.forename: Yun
authors.initials: Y
authors.lastname: Xia
authors.forename: Yunhong
authors.initials: Y
authors.lastname: Kong
authors.forename: Per Halkjaer
authors.initials: PH
authors.lastname: Nielsen
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D020562:Betaproteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D001896:Boron Compounds / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism*; D041862:Chloroflexi / Q000145:classification / Q000235:genetics / Q000378:metabolism; D017753:Ecosystem; D005456:Fluorescent Dyes / Q000378:metabolism*; D006868:Hydrolysis; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D002364:Caseins; D005456:Fluorescent Dyes; D011933:Reagent Kits, Diagnostic; D012722:Sewage; D012710:Serum Albumin, Bovine