Targeting the Mla Pathway: A Strategy to Combat Multidrug-Resistant Gram-Negative Bacteria University of Birmingham in United Kingdom

The emergence of antibiotic-resistant bacteria poses a serious and growing global threat, emphasizing the urgent need for new targets and strategies to combat infections. Multidrug resistance is particularly concerning in Gram-negative bacteria, with few antibiotics currently in development and limited prospects for new clinical treatments in the near future. Gram-negative bacteria tend to be more resistant to antibiotics, detergents, and other harmful chemicals than Gram-positive bacteria, primarily due to the presence of an additional outer membrane (OM) surrounding the cell.

This outer membrane has a complex lipid asymmetry, with lipopolysaccharides (LPS) in the outer layer and phospholipids in the inner layer, creating a highly effective barrier. This barrier blocks hydrophilic molecules and significantly slows the penetration of hydrophobic molecules, contributing to the bacteria's increased resistance to antibiotics and detergents. The outer membrane also contains proteins that play essential roles in microbial pathogenesis, virulence, and multidrug resistance, driving many of the processes responsible for infection and disease progression. These outer membrane proteins (OMPs) are crucial for cellular homeostasis, facilitating the excretion of toxic substances like antibiotics and aiding in nutrient uptake.

Understanding the biogenesis of the outer membrane is vital, both as a key biological process and as a potential pathway for developing new antibiotic targets. One such pathway, the Maintenance of outer membrane Lipid Asymmetry (Mla) system, is found in all Gram-negative bacteria and contributes to virulence, vesicle formation, and the preservation of the outer membrane’s barrier function. The Mla pathway maintains lipid asymmetry by removing misplaced lipids from the outer leaflet of the outer membrane and returning them to the inner membrane through three protein complexes: the MlaA-OmpC complex in the outer membrane, the periplasmic phospholipid shuttle protein MlaC, and the inner membrane ABC transporter complex MlaFEDB. Leveraging our expertise in structural biology and our focus on antimicrobial resistance, we will concentrate on developing inhibitors for the Mla pathway.

Using a combination of computational methods and high-throughput screening, we will identify potential hits. Biophysical and structural biology techniques will help determine binding modes, while synthetic chemistry will be employed to modify and enhance the properties of promising compounds. These candidates will then undergo various in vivo screening studies to assess their efficacy.

Funding notes:

1. Competition based funding available through the Midlands Integrative Biosciences Training Partnership - https://warwick . ac.uk/fac/cross_fac/mibtp/ https://www.birmingham . ac.uk/research/activity/mibtp

2. Competition based funding available through the Darwin Trust of Edinburgh

3. Self-funded Please contact [email protected] for more information regarding funding available

References:

Wotherspoon, P., Johnston, H., Hardy, D.J., Holyfield, R., Bui, S., Ratkeviciute, G., Sridhar, P., Colburn, J., Wilson, C.B., Colyer, A., Cooper, B.F., Bryant, J.A., Hughes, G.W., Stansfeld, P.J., Bergeron, J.R.C. and Knowles, T.J. (2024). "Structure of the MlaC-MlaD complex reveals molecular basis of periplasmic phospholipid transport." Nat Commun 15(1): 6394.