Extracellular Polymeric Substances of "Candidatus Accumulibacter": Composition, application and turnover

The majority of bacteria grow in the form of microbial aggregates known as biofilms. In these biofilms, microorganisms are embedded in a mixture of extracellular polymeric substances (EPS) produced by the microorganisms themselves. EPS is a complex mixture of biopolymers of different nature, such as polysaccharides, proteins, nucleic acids or lipids, among others. In spite of the significant progress over the last decades, EPS is still a black box waiting to be opened, in terms of specific composition, function, structure and production.Biofilms have great importance in many environmental engineering processes, as for example, aerobic granular sludge (AGS). AGS is a novel biological wastewater treatment where microorganisms are stimulated to form compact granules. Among the complex microbial community in AGS, polyphosphate accumulating organisms (PAOs) are of great importance, due to their role in phosphate removal and granule stabilization. Because of their dominance in AGS and their rapid anaerobic carbon sequestration, they are assumed to be the main EPS producer in AGS. Therefore, PAOs (specifically the well-studied “Candidatus Accumulibacter phosphatis”) can be used as model microorganism for the study of EPS of AGS.The goal of this thesis is to study the EPS of “Ca. Accumulibacter” in terms of specific composition, application and synthesis/consumption. A better characterization of the EPS of “Ca. Accumulibacter” will lead to a comprehensive understanding of this microorganism and further optimization of the granular sludge processes, and their application...