Quorum sensing and swarming migration in bacteria

Abstract

Bacterial cells can produce and sense signal molecules, allowing the whole population to initiate a concerted action once a critical concentration (corresponding to a particular population density) of the signal has been reached, a phenomenon known as quorum sensing. One of the possible quorum sensing-regulated phenotypes is swarming, a flagella-driven movement of differentiated swarmer cells (hyperflagellated, elongated, multinucleated) by which bacteria can spread as a biofilm over a surface. The glycolipid or lipopeptide biosurfactants thereby produced function as wetting agent by reducing the surface tension. Quorum sensing systems are almost always integrated into other regulatory circuits. This effectively expands the range of environmental signals that influence target gene expression beyond population density. In this review, we first discuss the regulation of AHL-mediated surface migration and the involvement of other low-molecular-mass signal molecules (such as the furanosyl borate diester AI-2) in biosurfactant production of different bacteria. In addition, population density-dependent regulation of swarmer cell differentiation is reviewed. Also, several examples of interspecies signalling are reported. Different signal molecules either produced by bacteria (such as other AHLs and diketopiperazines) or excreted by plants (such as furanones, plant signal mimics) might influence the quorum sensing-regulated swarming behaviour in bacteria different from the producer. On the other hand, specific bacteria can reduce the local available concentration of signal molecules produced by others. In the last part, the role and regulation of a surface-associated movement in biofilm formation is discussed. Here we also describe how quorum sensing may disperse existing biofilms and control the interaction between bacteria and higher organisms (such as the Rhizobium-bean symbiosis).

A Homologue of the 3-Oxoacyl-(Acyl Carrier Protein) Synthase III Gene Located in the Glycosylation Island of Pseudomonas syringae pv. tabaci Regulates Virulence Factors via N -Acyl Homoserine Lactone and Fatty Acid Synthesis

“…The results demonstrated that genes for iron metabolism were strongly induced in bacteria grown on swarming agar plates with less-nutritional conditions. It was reported that excess iron prevents swarming motility, and less-nutritional conditions may induce swarming and biosurfactant production in P. aeruginosa (7). From these reports, a reduced ability to acquire iron may relate to the hyperswarming motility in the ⌬orf3 mutant.…”

“…EPS production and tolerance to H 2 O 2 and antibiotics. Previous papers have reported that the production of EPS is regulated by quorum sensing and that an EPS-deficient mutant of P. syringae is hypersensitive to environmental stresses (7,17,25). To compare extracellular polysaccharide production on an MMMF plate with 1.5% agar after 48 h of incubation at 27°C, each mutant was scraped off and the amounts of extracellular polysaccharide and extracellular proteins as an internal control were quantified (Fig.…”

“…tabaci 6605 synthesized OHHL and HHL as major AHLs, whereas the ⌬orf3 mutant had a significantly reduced ability to produce AHLs. The quorum-sensing system using AHL signals is a recently well-studied bacterial mechanism that unicellular organisms use to communicate with each other and act like multicellular organisms by monitoring their own population density (7). The orf3 gene is thought to participate in this system by supplementation of AHL precursors.…”

New advances in plant growth-promoting rhizobacteria for bioremediation

“…In addition, AMF as well as quantities of other microbes also exist in the rhizosphere, such as P-solubilizing bacteria and mycorrhizal-helping bacteria (MHB) initiate a concerted action when a particular population density is achieved, i.e., quorum sensing (Khan, 2005). This phenomenon expands the environmental signals to a larger range (Daniels et al, 2004). The involvement of fungi is beyond the scope in our review and will not be further discussed.…”

Proteus mirabilis interkingdom swarming signals attract blow flies

“…Acylhomoserine lactones in Gram-negative bacteria as well as indole, and autoinducer 2 in both Gram-negative and Grampositive bacteria (Jayaraman and Wood, 2008;Han et al, 2010) are typical QS signals. QS regulates swarming motility (Daniels et al, 2004).…”