Pyoverdine-mediated iron transport in Pseudomonas aeruginosa: involvement of a high-molecular-mass outer membrane protein.

Reduced expression of an iron-regulated outer membrane protein (IROMP) of approximate molecular mass 90,000 was observed in Pseudomonas aeruginosa concomitant with a loss of pyoverdine production in a wild type strain grown at 43 degrees C and in a mutant deficient in pyoverdine production. Consistent with an implied role in pyoverdine-mediated iron transport a mutant lacking the 90 kDa protein transported barely detectable levels of ferri-pyoverdine. Interestingly, the mutant still exhibited pyoverdine-dependent growth in an iron-deficient medium containing the synthetic iron chelator ethylene diamine-di(omicron-hydroxyphenol acetic acid) (EDDHA) suggesting that a second uptake system for ferri-pyoverdine may exist in P. aeruginosa.