Signaling in Escherichia coli Biofilms

Cell signaling in Escherichia coli biofilms is more important than originally known, in that autoinducer two (AI-2), AI-1 (N-acylhomoserine lactones), indole, hydroxylated indoles, norepinephrine, and epinephrine are all functional signals in this organism. This gives the bacterium the ability to monitor not only the presence of cells of its own species (through AI-2 and indole) but also the activity of the human host (through norepinephrine and epinephrine) as well as that of the other commensal bacteria (through hydroxylated indoles). We have also found that E. coli monitors the presence of bacteria that produce acylhomoserine lactones as these signals influence formation of its biofilms through the LuxR homolog SdiA. Hence, E. coli monitors its surroundings through signals it synthesizes as well as those synthesized by both prokaryotes and eukaryotes. In this chapter, we present recent findings on the role of these different signals as well as provide a detailed account of the complex features of uptake and regulation of the AI-2 signal in E. coli. AI-2 signaling through the motility quorum sensing regulator,