Extracellular polymeric substances in microbial biofilms

Publisher Summary A definition of microbial biofilms systems may be based on biofilm structure or on biofilm function. Structurally defined, biofilm systems are microorganisms and their extracellular polymeric substances associated with an interface. In this definition, microorganisms, are understood in the broadest sense including bacteria, Archaea, as well as eukaryotic microorganisms, i.e., protozoa, algae, and fungi. The term “interfaces” does include any possible type: liquid–liquid, solid–liquid, gas–liquid, or solid–gas. As a major component of biofilm systems, the extracellular polymeric substances produced by the members in a specific biofilm system are explicitly included in this definition. Functionally defined, biofilms are spatially structured communities of microbes whose function is dependent upon a complex web of symbiotic interactions. Apart from cellular constituents, a second major component of biofilm systems is represented by the polymer matrix. The extracellular polymeric substances (EPS) of the biofilm matrix appear to have several key properties and functions. In this chapter, the nature of biofilm and EPS is discussed, and a survey of the main literature on the biofilm matrix is provided. The chapter introduces a novel concept on EPS functionality to elaborate on EPS functions, to raise the discussion on biofilm EPS, to implement further studies using different biofilm systems, and to trigger new approaches and hypotheses.