Pseudomonas aeruginosa response to lung surfactant

The response of bacteria to the conditions at the site of infection is a key part of the transcriptional program that will determine the sucess of the infectious agent. To model the environment of the distal airway, we used bovine pulmonary surfactant (Survanta). P. aeruginosa transcript levels were measured in the presence or absence of Survanta in MOPS minimal medium to identify transcripts altered in response to surfactant. The most highly induced transcript in Survanta was PA5325, renamed sphA based on our findings that the gene was specifically induced by sphingosine derived from the sphingomyelin present in pulmonary surfactant. A divergently transcribed transcription factor, PA5324, was demonstrated to be critical for the sphingosine dependent induction of sphA and was therefore renamed SphR. Microarrays of the sphR mutant cells were compared to wild type to determine the likely SphR regulon. Wild type and sphR mutant cells were pre-grown in MOPS minimal media and then split and resuspended in MOPS pyruvate or MOPS pyruvate + surfactant