IRON UPTAKE IN PSEUDOMONAS-AERUGINOSA MEDIATED BY N-(2,3-DIHYDROXYBENZOYL)-L-SERINE AND 2,3-DIHYDROXYBENZOIC ACID

Pseudomonas aeruginosa is known to have an inducible uptake system for the enterobacterial siderophore enterobactin. In this work we have ex amined iron transport mediated by the biosynthetic precursor 2,3-dihyd roxybenzoic acid and N-(2,3-dihydroxybenzoyl)-L-serine, a breakdown pr oduct of enterobactin. Iron complexed with 2,3-dihydroxybenzoyl-S-seri ne was transported into P. aeruginosa IA1 via a transport system which is energy-dependent and iron-repressible. The rate of transport was n ot altered by growing the cells in the presence of either pyoverdin or pyochelin, which have been shown previously to induce transport via t hat system. Growth of the cells in the presence of enterobactin did ca use an increase in the rate of transport, indicating that the complex can be transported by the inducible enterobactin uptake system, but al so that a separate system must exist. In contrast, transport of iron c omplexed with 2,3-dihydroxybenzoic acid was neither iron-repressible n or strongly energy-dependent, from which we conclude that there must b e a novel mode of transport not characteristic of iron-siderophore tra nsport systems.