Analysis of Gene Expression in Biofilm Bacteria

Abstract

Microbial processes that are of economic, medical, dental or environmental consequence occur with the organisms immobilized on a surface. Early studies with in vitro grown biofilms demonstrated that the phenotypic properties of adherent organisms differed from their planktonic counterparts.⁷ These results are now being reinforced by new studies that are using a wide variety of bacterial species and novel methods. It is also becoming apparent that the phenotypic changes seen with adherent organisms, as with suspended populations, are due to sensing by the organisms of environmental stimuli which signal changes in the patterns of expression of particular genes. In some cases, the organisms appear to sense binding to the surface, as in the case of Escherichia coli or Pseudomonas aeruginosa.^8,14 More commonly, local environmental conditions arising as a result of mass transport limitations, synergistic and antagonistic activities of biofilm bacteria, intercellular signaling and so forth, may induce bacteria to modulate expression of genes differently than suspended populations growing under very similar conditions.² Clearly, if a comprehensive view of the characteristics of adherent populations is to be developed, it will be essential to incorporate a thorough understanding of 1) how gene expression differs between suspended and sessile organisms, 2) what, if any, genetic control circuits are peculiar to biofilm growth, and 3) how global and/or biofilm specific genetic circuits crosstalk with one another in adherent bacteria.