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Applied and Environmental Microbiology, March 2008, p. 1517-1526, Vol. 74, No. 5
0099-2240/08/$08.00+0     doi:10.1128/AEM.02274-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Amyloid-Like Adhesins Produced by Floc-Forming and Filamentous Bacteria in Activated Sludge{triangledown}

Poul Larsen, Jeppe Lund Nielsen, Daniel Otzen,{dagger} and Per Halkjær Nielsen*

Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark

Received 6 October 2007/ Accepted 26 December 2007

Amyloid proteins (fimbriae or other microbial surface-associated structures) are expressed by many types of bacteria, not yet identified, in biofilms from various habitats, where they likely are of key importance to biofilm formation and biofilm properties. As these amyloids are potentially of great importance to the floc properties in activated sludge wastewater treatment plants (WWTP), the abundance of amyloid adhesins in activated sludge flocs from different WWTP and the identity of bacteria producing these were investigated. Amyloid adhesins were quantified using a combination of conformationally specific antibodies targeting amyloid fibrils, propidium iodide to target all fixed bacterial cells, confocal laser scanning microscopy, and digital image analysis. The biovolume fraction containing amyloid adhesins ranged from 10 to 40% in activated sludge from 10 different WWTP. The identity of bacteria producing amyloid adhesins was determined using fluorescence in situ hybridization with oligonucleotide probes in combination with antibodies or thioflavin T staining. Among the microcolony-forming bacteria, amyloids were primarily detected among Alpha- and Betaproteobacteria and Actinobacteria. A more detailed analysis revealed that many denitrifiers (from Thauera, Azoarcus, Zoogloea, and Aquaspirillum-related organisms) and Actinobacteria-related polyphosphate-accumulating organisms most likely produced amyloid adhesins, whereas nitrifiers did not. Many filamentous bacteria also expressed amyloid adhesins, including several Alphaproteobacteria (e.g., Meganema perideroedes), some Betaproteobacteria (e.g., Aquaspirillum-related filaments), Gammaproteobacteria (Thiothrix), Bacteroidetes, Chloroflexi (e.g., Eikelboom type 1851), and some foam-forming Actinobacteria (e.g., Gordonia amarae). The results show that amyloid adhesins were an abundant component of activated sludge extracellular polymeric substances and seem to have unexpected, divers functions.

* Corresponding author. Mailing address: Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark. Phone: 45 99408503. Fax: 45 96350558. E-mail: phn{at}bio.aau.dk

{triangledown} Published ahead of print on 11 January 2008.

{dagger} Present address: Interdisciplinary Nanoscience Centre, Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10C, DK 8000 Aarhus C, Denmark.

Applied and Environmental Microbiology, March 2008, p. 1517-1526, Vol. 74, No. 5
0099-2240/08/$08.00+0     doi:10.1128/AEM.02274-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Jordal, P. B., Dueholm, M. S., Larsen, P., Petersen, S. V., Enghild, J. J., Christiansen, G., Hojrup, P., Nielsen, P. H., Otzen, D. E. (2009). Widespread Abundance of Functional Bacterial Amyloid in Mycolata and Other Gram-Positive Bacteria. Appl. Environ. Microbiol. 75: 4101-4110 [Abstract] [Full Text]  


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