Primitive But Intelligent: Bacterial Quorum Sensing - Lecture Notes | MCB 741, Papers of Biology

MCB 741 Yanyan Cao

Primitive but intelligent ---- Bacterial quorum sensing

Bacteria are the simplest creatures that are considered alive nowadays. Although it has long been known

that bacteria are able to secrete secondary metabolites, not until the late 1960s had we realized that such

simple organisms are able to “talk” to each other using some of the secreted metabolites. Those

molecular messengers were later named as autoinducers (1). The phenomenon of employing

autoinducers by bacteria to regulate gene expression to coordinate community behavior in response to

cell density was termed “quorum sensing” (1).

Quorum sensing was first described by Hastings’s group in 1970 when they observed that the

pool of autoinducers has been expanding (6, 7). For instance, two other AHL family autoinducers and a

novel 4-hydroxy-2-alkylquinoline (HAQ) family autoinducer, 2-heptyl-3-hydroxy-4-quinolone (PQS)

have been identified in human facultative pathogen Pseudomonas aeruginosa (8-10). Interestingly,

recent studies recruited various antibiotics to the autoinducer group. It has been revealed that some

antibiotics at subinhibitory concentrations are not only able to activate some chromosomal gene

promoters (11-13) but also modulate some physical characteristics of communities (12). As an example,

the P. aeruginosa pigment pyocyanin, which possesses antibiotic activity, upregulates the expression of

a cluster of genes involved in virulence (13) and favors the formation of confined and smooth colonies

on the way to identify a novel target for antimicrobial drug therapy (14).