title: Acyl-homoserine lactones modulate the settlement rate of zoospores of the marine alga Ulva intestinalis via a novel chemokinetic mechanism.
abstract: Bacteria utilize quorum sensing to regulate the expression of cell density-dependant phenotypes such as biofilm formation and virulence. Zoospores of the marine alga Ulva intestinalis exploit the acyl-homoserine lactone (AHL) quorum sensing system to identify bacterial biofilms for preferential settlement. Here, we demonstrate that AHLs act as strong chemoattractants for Ulva zoospores. Chemoattraction does not involve a chemotactic orientation towards the AHL source. Instead, it occurs through a chemokinesis in which zoospore swimming speed is rapidly decreased in the presence of AHLs. The chemoresponse to AHLs was dependant on the nature of the acyl side chain, with N-(3-oxododecanoyl)-homoserine lactone (30-C12-HSL) being the most effective signal molecule. Mean zoospore swimming speed decreased more rapidly over wild-type biofilms of the marine bacteria Vibrio anguillarum relative to biofilms of the vanM mutant, in which AHL synthesis is disrupted. These data implicate a role for AHL-mediated chemokinesis in the location and preferential settlement of Ulva zoospores on marine bacterial assemblages. Exposure to AHLs did not inhibit the negative phototaxis of Ulva zoospores, indicating that chemoattraction to bacterial biofilms does not preclude the response to a light stimulus in substrate location.
authors.affiliation: Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK. glw@pml.ac.uk
authors.forename: Glen L
authors.initials: GL
authors.lastname: Wheeler
authors.forename: Karen
authors.initials: K
authors.lastname: Tait
authors.forename: Alison
authors.initials: A
authors.lastname: Taylor
authors.forename: Colin
authors.initials: C
authors.lastname: Brownlee
authors.forename: Ian
authors.initials: I
authors.lastname: Joint
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D018441:Biofilms; D002630:Chemotactic Factors / Q000235:genetics / Q000494:pharmacology*; D002633:Chemotaxis / Q000502:physiology; D008027:Light; D015398:Signal Transduction; D013170:Spores / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D044445:Ulva / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014733:Vibrio / Q000235:genetics / Q000378:metabolism
chemical_list: D002630:Chemotactic Factors; C088386:homoserine lactone; D015107:4-Butyrolactone