| Abstract: | Previously, we reported that the speA gene, encoding arginine decarboxylase, isrequired for swarming in the urinary tract pathogen Proteus mirabilis. In addition,this previous study suggested that putrescine may act as a cell-to-cell signaling molecule(Sturgill, G., and Rather, P. N. (2004) Mol. Microbiol. 51, 437–446). Inthis new study, PlaP, a putative putrescine importer, was characterized in P.mirabilis. In a wild-type background, a plaP null mutation resulted in amodest swarming defect and slightly decreased levels of intracellular putrescine. In a P.mirabilis speA mutant with greatly reduced levels of intracellular putrescine,plaP was required for the putrescine-dependent rescue of swarming motility. When aspeA/plaP double mutant was grown in the presence of extracellular putrescine, theintracellular levels of putrescine were greatly reduced compared with the speAmutant alone, indicating that PlaP functioned as the primary putrescine importer. In urothelial cellinvasion assays, a speA mutant exhibited a 50% reduction in invasion whencompared with wild type, and this defect could be restored by putrescine in a PlaP-dependent manner.The putrescine analog Triamide-44 partially inhibited the uptake of putrescine by PlaP and decreasedboth putrescine stimulated swarming and urothelial cell invasion in a speAmutant. |
