text: Some of the best-known examples of quorum sensing come from studies of bacteria. Bacteria use quorum sensing to regulate certain phenotype expressions, which in turn, coordinate their behavio rs. Some common phenotypes include biofilm formation, virulence factor expression, and motility. Certain bacteria are able to use quorum sensing to regulate bioluminescence, nitrogen fixation and sporulation.
  The quorum-sensing function is based on the local density of the bacterial population in the immediate environment. It can occur within a single bacterial species, as well as between diverse species. Both gram-positive and gram-negative bacteria use quorum sensing, but there are some major differences in their mechanisms.