We study responses of bacterium Escherichia coli to the changing physical and chemical properties of its environment.  Commensal E. coli strains inhabitant the colons of healthy humans and animals.  Pathogenic E. coli strains cause diseases when they colonize intestinal or urinary tracts, or the meninges’ of infants.  E. coli is transmitted among humans and animals via food and water.  E. coli has a remarkable ability to cope with the varying osmotic pressure, temperature and chemistry of these environments.

E. coli uses osmoregulatory mechanisms to survive osmotic pressure changes.  The complex osmoregulatory machinery of E. coli includes proteins ProP and ProQ.  The first protein shown to function as an osmosensory transporter in any organism, ProP detects increasing osmotic pressure and responds by pumping osmolytes into the cytoplasm to prevent cellular dehydration.  Osmolytes are small molecules that stabilize the structures and interactions of proteins and nucleic acids.  ProQ is an RNA-binding protein that controls the cellular level of ProP.  We use genetic, molecular biological, biochemical and biophysical tools to learn how proteins ProP and ProQ fulfill those roles.

Osmolyte accumulation may also help E. coli to tolerate heat, cold, oxygen radicals and urea.  Many osmolytes and osmolyte transporters that confer osmotic stress tolerance on E. coli have been identified.  We are testing predictions, based on “omic” studies, that additional osmolytes and transporters contribute to the survival of commensal or pathogenic E. coli strains.

Our ultimate aim is to elucidate mechanisms that promote the health of microbial, animal and plant cells by showing how they sense and control their own physical and chemical properties.