Exopolysaccharides in biofilms, flocs and related structures

In biofilms, flocs and similar multispecies microbial communities, exopolys accharides (EPSs) are always present, frequently as the major component oth er than water. The EPSs vary widely in their composition, structure and pro perties and thus it is impossible to generalise about their contribution to biofilm or floc structure. Relatively few of the polymers obtained from bi ofilms and flocs have been adequately purified and analysed but such eviden ce as is so far available suggests that the polysaccharides closely resembl e those synthesised by the corresponding planktonic bacteria. From a knowle dge of the physical properties of these, if is now possible to present a re asonably accurate picture of some of the factors which they may contribute to the structure and stability of complex aggregates of micro-organisms in biofilms and flocs.