Characterization of the norspermidine/spermidine ABC-type transporter, PotABCD1, in Vibrio cholerae

Vibrio cholerae is an intestinal pathogen that also thrives in aquatic environments through forming biofilms, matrix-bound aggregation of cells offering physical protection from many environmental stressors. Formation of biofilm can be regulated by various environmental signals including molecules called polyamines. Polyamines are a ubiquitous class of molecules that are involved in cell growth and regulate a wide variety of functions through mechanisms including transport. Bacteria contain polyamine transport systems, generally ABC transporters. V. cholerae has a putative ABC transporter, PotABCD1. Previous research in our lab has investigated the role of the substrate binding protein, PotD1 and has shown that PotD1 is responsible for transport of the polyamines spermidine and norspermidine into V. cholerae. Moreover, PotD1 mutants displayed an increased biofilm phenotype when compared with wild type. The roles of the other components of the polyamine transport system still need further investigation. The objectives of this study were to more thoroughly characterize the norspermidine/spermidine uptake system and determine whether imported polyamines or the components of the transporter system affect biofilm formation. This work not only establishes PotABCD1 as the first norspermidine transporter ever reported in any species, but also further elucidates the role polyamines play in V. cholerae biofilm formation.