Abstract
Previously, we reported that the speA gene, encoding arginine decarboxylase, is required 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). In this new study, PlaP, a putative putrescine importer, was characterized in P. mirabilis. In a wild-type background, a plaP null mutation resulted in a modest 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 a speA/plaP double mutant was grown in the presence of extracellular putrescine, the intracellular levels of putrescine were greatly reduced compared with the speA mutant alone, indicating that PlaP functioned as the primary putrescine importer. In urothelial cell invasion assays, a speA mutant exhibited a 50% reduction in invasion when compared 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 decreased both putrescine stimulated swarming and urothelial cell invasion in a speA mutant.
Highlights
Polyamines play roles in bacterial cell-to-cell signaling processes
An E. coli mutant deficient in putrescine synthesis (⌬speAB and ⌬speC) and missing the polyamine importers PotABCD and YdcSTUV was dependent on both putrescine and the putrescine importer PlaP for surface motility on semisolid media [12]
The plaP::Cm mutation was first constructed in a P. mirabilis speA::Km mutant deficient in putrescine biosynthesis, as the lower intracellular levels of putrescine in this background would emphasize a role for PlaP in putrescine import
Summary
Results: In Proteus mirabilis, PlaP is important for putrescine uptake, swarming motility, and urothelial cell invasion, and the putrescine transport inhibitor Triamide-44 inhibits these processes. We reported that the speA gene, encoding arginine decarboxylase, is required for swarming in the urinary tract pathogen Proteus mirabilis. This previous study suggested that putrescine may act as a cell-to-cell signaling molecule In a P. mirabilis speA mutant with greatly reduced levels of intracellular putrescine, plaP was required for the putrescinedependent rescue of swarming motility. We report that PlaP is important for putrescine uptake, swarming motility, and urothelial cell invasion of P. mirabilis. The inhibition of putrescine uptake using the putrescine transport inhibitor Triamide-44 decreased swarming and urothelial cell invasion
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