A Novel Putrescine Importer Required for Type 1 Pili-driven Surface Motility Induced by Extracellular Putrescine in Escherichia coli K-12

Recently, many studies have reported that polyamines play a role in bacterial cell-to-cell signaling processes. The present study describes a novel putrescine importer required for induction of type 1 pili-driven surface motility. The surface motility of the Escherichia coli Delta speAB Delta speC Delta potABCD strain, which cannot produce putrescine and cannot import spermidine from the medium, was induced by extracellular putrescine. Introduction of the gene deletions for known polyamine importers (Delta potE, Delta potFGHI, and Delta puuP) or a putative polyamine importer (Delta ydcSTUV) into the Delta speAB Delta speC Delta potABCD strain did not affect putrescine-induced surface motility. The deletion of yeeF, an annotated putative putrescine importer, in the Delta speAB Delta speC Delta potABCD Delta ydcSTUV strain abolished surface motility in putrescine-supplemented medium. Complementation of yeeF by a plasmid vector restored surface motility. The surface motility observed in the present study was abolished by the deletion of fimA, suggesting that the surface motility is type 1 pili-driven. A transport assay using the yeeF(+) or Delta yeeF strains revealed that YeeF is a novel putrescine importer. The K-m of YeeF (155 mu M) is 40 to 300 times higher than that of other importers reported previously. On the other hand, the V-max of YeeF (9.3 nmol/min/mg) is comparable to that of PotABCD, PotFGHI, and PuuP. The low affinity of YeeF for putrescine may allow E. coli to sense the cell density depending on the concentration of extracellular putrescine.