Editor: Michael Wagner
In situ detection of protein-hydrolysing microorganisms in activated sludge
Article first published online: 22 FEB 2007
FEMS Microbiology Ecology
Volume 60, Issue 1, pages 156–165, April 2007
How to Cite
Xia, Y., Kong, Y. and Nielsen, P. H. (2007), In situ detection of protein-hydrolysing microorganisms in activated sludge. FEMS Microbiology Ecology, 60: 156–165. doi: 10.1111/j.1574-6941.2007.00279.x
- Issue published online: 22 FEB 2007
- Article first published online: 22 FEB 2007
- Received 12 July 2006; revised 17 November 2006; accepted 24 November 2006.First published online 22 February 2007.
- protein-hydrolyzing organisms;
- activated sludge;
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.