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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/32062

Title: Bacterial Adhesin Proteins Associated with Microbial Flocs and EPS in the Activated Sludge
Authors: Brei, Elena
Advisor: Liss, Steven N.
Department: Chemical Engineering and Applied Chemistry
Keywords: adhesin proteins
flocs
Issue Date: 19-Jan-2012
Abstract: Microbial flocculation is important in wastewater treatment process for an efficient separation of the solid and liquid phases and the removal of organics. Bacterial adhesins may contribute to the formation of microbial flocs since they have been previously found to play a significant role in the formation of biofilms. The overall objective of this work was to analyze bacterial protein adhesins present in the extracellular polymeric substances (EPS), mainly those associated with pili, fimbriae, flagella, and curli, and to determine their role in microbial floc structure and function. Identification of these EPS adhesins may explain their role in biofouling and enhance our understanding regarding the manipulation of bioflocculation. With the exception of flagellin protein FliC, which was distributed towards the outer region of the floc, all the adhesins appeared to be concentrated within the core region of the floc. Antibody staining coupled with confocal microscopy indicated that adhesin proteins associated with flagella (FliC), pili (PilA), fimbriae (FimH), and curli (CsgA, CsgB) represent a significant fraction (10-27%) within microbial flocs. Western blot analyses demonstrated that with the exception of FliC, all the studied adhesins were detected in the EPS matrix. Furthermore, mass spectrometry indicated the presence of pili in the EPS matrix. Under Phosphorus (P)-limited conditions, with the exception of fliC, all the studied genes (fimH, pilO, psiF) exhibited a change in response to P reduction, with fimH gene at the highest expression and an earliest response (1 d). During the nutritional downshift analyses, fimH and pilO genes were expressed within the first six hours of the reaction at significantly greater levels than during P-limited conditions. Taken together, these studies suggest that adhesins associated with pili, fimbriae, and curli play an important role in initial floc formation, and that adhesins associated with flagella either recruit planktonic bacteria to a growing floc or are involved in the interfacial relationships at the floc surface. This information may assist researchers and engineers in broadening the understanding of bioflocculation in conventional biologically based wastewater treatment systems and in advanced technologies, such as hybrid and membrane bioreactors. In addition, this knowledge will be useful in creating molecular tools to aid in the design and monitoring of bioflocculation.
URI: http://hdl.handle.net/1807/32062
Appears in Collections:Doctoral

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