title: 12-Methyltetradecanoic acid, a branched-chain fatty acid, represses the extracellular production of surfactants required for swarming motility in Pseudomonas aeruginosa PAO1.
abstract: Pseudomonas aeruginosa is known to produce surfactants that are involved in its  swarming motility behavior, such as rhamnolipids and their precursors-3-(3-hydroxyalkanoyloxy)-alkanoic  acids (HAAs). In P. aeruginosa PAO1, swarming motility is inhibited by some fatty acids, including  branched-chain fatty acids and unsaturated fatty acids. In the present study, addition of  12-methyltetradecanoic acid (12-MTA, anteiso-C15:0) to an agar medium markedly repressed  surfactant activity in the extracellular fraction of a P. aeruginosa culture in a drop collapse  assay. Further, an extracellular fraction of a culture of rhlA mutant P. aeruginosa, which did not  produce both rhamnolipids and HAAs, showed a complete loss of surfactant activity and markedly  reduced swarming activity. In contrast, an extracellular fraction of a culture of rhlB mutant  P. aeruginosa, which produced HAAs but not rhamnolipids, showed moderate swarming activity and  weak extracellular surfactant activity that was lost on the addition of 12-MTA to the agar medium.  Expression of the rhlAB operon from the plasmid pMR2 restored normal swarming motility on  12-MTA-containing agar medium. Taken together, these findings indicate that 12-MTA reduced  extracellular surfactant activity, thus resulting in a swarming defect in P. aeruginosa PAO1.
authors.affiliation: Department of Oral Microbiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan.
authors.forename: Tetsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Teruo
authors.initials: T
authors.lastname: Kuroda
authors.forename: Naoya
authors.initials: N
authors.lastname: Ohara
mesh_terms: D003470:Culture Media / Q000737:chemistry; D005227:Fatty Acids / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D006801:Humans; D008124:Locomotion; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D013501:Surface-Active Agents / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005227:Fatty Acids; D013501:Surface-Active Agents; C069642:aseanostatin P5