Pseudomonas fluorescens ompW: plasmid localization and requirement for naphthalene uptake

Suppressive subtractive hybridization has been utilized to generate a cDNA library of genes differentially expressed in naphthalene grown cells of Pseudomonas fluorescens. The library was devoid of genes known to be associated with naphthalene catabolism, but was enriched in genes related to cellular uptake and efflux systems. The gene for OmpW, which was present in the cDNA library and has been proposed to encode a porin for the transport of hydrophobic molecules, was isolated, cloned, and sequenced. This gene was shown to be exclusively localized on a large catabolic plasmid possessed by the organism, and its specific mutation resulted in the loss of the organism's ability to grow on naphthalene and several other polycyclic aromatic hydrocarbons. It is proposed that a primary response by P. fluorescens to the presence of naphthalene is the elevation of the cellular mechanism(s) required for its assimilation. The presence of genes related to the uptake and efflux mechanisms present following suppressive subtractive hybridization supports this proposal.