text: In the gram-negative bacterium Escherichia coli (E. coli), cell division may be partially regulated by AI-2-mediated quorum sensing. This species uses AI-2, which is produced and processed by the lsr operon. Part of it encodes an ABC transporter, which imports AI-2 into the cells during the early stationary (latent) phase of growth. AI-2 is then phosphorylated by the LsrK kinase, and the newly produced phospho-AI-2 can be either internalized or used to suppress LsrR, a repressor of the lsr operon (thereby activating the operon). Transcription of the lsr operon is also thought to be inhibited by dihydroxyacetone phosphate (DHAP) through its competitive binding to LsrR. Glyceraldehyde 3-phosphate has also been shown to inhibit the lsr operon through cAMP-CAPK-mediated inhibition. This explains why, when grown with glucose, E. coli will lose the ability to internalize AI-2 (because of catabolite repression). When grown normally, AI-2 presence is transient.
  E. coli and Salmonella enterica do not produce AHL signals commonly found in other gram-negative bacteria. However, they have a receptor that detects AHLs from other bacteria and change their gene expression in accordance with the presence of other "quorate" populations of gram-negative bacteria. AHL quorum sensing regulates a wide range of genes through cell density. Other species of bacteria produce AHLs that Eschericia and Salmonella can detect. E.coli and Salmonella produce a receptor like protein (SdiA) allowing the amino acid sequence that is similar to AHL show AHLs can be found in the bovine rumen and E. Coli responds to AHLs taken out of the bovine rumen. Most animals do not have AHL in their gastrointestinal tracts.