Elucidating the mechanisms of lipid transport in gram negative bacteria

The asymmetric outer membrane (OM) of gram-negative bacteria, comprised of lipopolysaccharide and phospholipid in the inner and outer leaflets respectively, provides an impermeable barrier to hydrophilic molecules whilst also slowing the penetration of small hydrophobic molecules. Due to this sophisticated barrier, Gram-negative bacteria generally display elevated resistance to antibiotics, detergents and other toxic chemicals than their Gram-positive counterparts hence combatting Gram-negative pathogens can be somewhat problematic. Mutations disrupting membrane integrity increase chemical susceptibility and reduce virulence hence OM biosynthetic and maintenance pathways may provide efficacious targets for novel antimicrobials.
The pathways by which LPS is synthesised, trafficked to and finally inserted within the OM are well documented however those responsible for trafficking phospholipids to the OM and those maintaining the critical OM asymmetry remain enigmatic. Recently members of the MCE protein superfamily have been implicated in the transport of lipids between the inner and outer membranes of Gram-negative bacteria. E coli contains three MCE proteins MlaD, PqiB and YebT each residing in unique operons hence multiple lipid transport pathways may exist.

This project will probe the structure and function of the Pqi pathway components (PqiA-C) using a range of biophysical techniques to determine: (1) If the Pqi pathway is involved in lipid transport. (2) The mechanisms by which Pqi facilitated lipid transport is performed (3) The role of the Pqi pathway in pathogenesis.