Role of extracellular polymeric substances (EPS) production in bioaggregation: application to wastewater treatment

A review concerning the definition, extraction, characterization, production and functions of extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment reactors is given in this paper. EPS are a complex high-molecular-weight mixture of polymers excreted by microorganisms, produced from cell lysis and adsorbed organic matter from wastewater. They are a major component in microbial aggregates for keeping them together in a three-dimensional matrix. Their characteristics (e.g., adsorption abilities, biodegradability and hydrophilicity/hydrophobicity) and the contents of the main components (e.g., carbohydrates, proteins, humic substances and nucleic acids) in EPS are found to crucially affect the properties of microbial aggregates, such as mass transfer, surface characteristics, adsorption ability, stability, the formation of microbial aggregates etc. However, as EPS are very complex, the knowledge regarding EPS is far from complete and much work is still required to fully understand their precise roles in the biological treatment process. Copyright © 2010 Elsevier Inc. All rights reserved.

Bacteria employ sophisticated cell-to-cell communication or 'quorum sensing' (QS) systems for promoting collective behaviours that depend on the actions of one or more chemically distinct diffusible signal molecules. As determinants of cell population density, multiple QS systems are often integrated with each other and within global regulatory networks and subject to the prevailing environmental conditions as well as the presence and activities of other organisms. QS signal molecules, although largely considered as effectors of QS-dependent gene expression are also emerging as multifunctional molecules that influence life, development and death in single and mixed microbial populations and impact significantly the outcome of host-pathogen interactions.