"Quorum sensing" signal mechanisms of bacteria. Review article

"Quorum sensing" (QS) signal mechanisms represent special forms of interbac terial actions which make the sensing of cell density of a given bacterial population possible and which will - independently from the available nutri ent - inhibit bacterial growth of the culture above a certain tolerable lim it. Examples of QS mechanisms of streptococci, Staphylococcus aureus, and Enter ococcus faecalis are briefly mentioned. The acyl-homoserine-lactone (AHL) s ignal and receptor systems, frequently encountered in Gram negative bacteri a are reviewed: details are given on the AHL signalpeptids and correspondin g receptors of the marine vibrios (Vibrio harveyi and V.fischeri) regulated by the luxs and luxr genes respectively. The "quorum sensing" system of Ps eudomonas aeruginosa is more complex: containing a special Pseudomonas quin olon signal (PQS), and other small diffusible molecules, besides AHL. A separate chapter is devoted to the interbacterial communication mechanism s of Escherichia coli and Salmonella. Beside the known colicin (and bacteri ocin) systems these are also containing the production of inhibitory molecu les regulated by the sdia and lux genes, These (and other similar) mechanis ms result inhibition of intestinal colonization (in vivo), and the growth i nhibition (in vitro). Significance of these mechanisms in science and techn ology is pointed out.