INTRODUCTION

A perusal of the published literature might lead the naïve to believe that microbial biofilms are definable entities each of which, whilst possessing characteristics that are markedly dissimilar from their planktonic equivalents, has its own defined physiology and architecture. Thus it is easy to imagine, rather like for our own bodies, that the visible, physical manifestation has a degree of permanency. The reality is that the structures known as biofilms, as well as the majority of tissues that make up our bodies, are in a state of dynamic flux/turnover. Modern imaging techniques generally give us snapshots in time and only rarely give an indication of the turmoil within (Costerton et al., 1995).

It is the intention of this article to dispel any view the reader might have entertained of biofilms being static entities. Dynamics within microbial biofilm communities will be considered in terms of their spatial stability (movement/drift), and changes in biomass, genetic diversity and community function. In the latter respects, population dynamics will be considered for both short-term events, such as the formation and establishment of biofilm communities on ‘virgin’ surfaces (Geesey et al., 1992), and long-term events, with biofilms being considered as units of proliferation/evolution (Caldwell et al., 1997).

Dynamics in microbial communities can be considered on a number of distinct levels, many of which have been considered separately in this symposium volume. The first of these relates to the spatial stability of the biofilm community. Matrix polymers not only glue the biofilm to the surface but also enable spatial organization to be imposed on the community. The polymers are plastic and may be physically deformed through the imposition of shear forces from the fluid phase.