FIG 8.

Proposed model of a static dual-species biofilm, in comparison to a single-species E. coli biofilm. E. faecalis is an active AI-2 producer, and its aggregates attract E. coli cells expressing LsrB. Cocultivation of E. coli with E. faecalis in static systems results in higher levels of extracellular AI-2, which helps E. coli cells to maintain lsr operon expression at low cell densities and to coaggregate effectively with E. faecalis, which creates nucleation zones for subsequent enhanced aggregate growth and biofilm formation. These coaggregates of E. coli and E. faecalis are more resistant to stress.