This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Quorum sensing (QS) is a mechanism by which many prokaryotes are able to sense and respond to the environment by modification of gene expression. Responses are population dependent and are elicited through the secretion of an autoinducer molecule (AI) which, in high concentration, diffuses back across the cell membrane and modifies gene expression. Such signal reception is critical for the gene expression changes that are part of the pathogenicity of P. aeruginosa in cystic fibrosis. To determine the role of membrane lipid composition in QS signal transmission and reception, membrane lipid profiles from log phase Pseudomonas aeruginosa strains PAO1 and PAO-JP2, grown under typical laboratory conditions, were extracted, identified and quantitated using GC-MS. Profiles from PAO1 and the AI mutant PAO-JP2 were identical, indicating that the QS mutations did not cause altered membrane composition under normal growing conditions. Fresh cultures of PAO-JP2 were then subjected to a variety of stressful growing conditions (low pH, high salt, antibiotics) until the membrane fractions showed a compositional change indicating that the cells were responding to the environmental stress. Using growing conditions demonstrated to stimulate altered membrane composition, cultures of PAO-JP2 were grown to log phase in both normal and stressful conditions, AI added to the culture, and the resulting modification of gene expression qualtitated by DNA microarray analysi
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