Illustration of LpxA, the first enzyme in the lipid A biosynthesis pathway, from the bacterium Pseudomonas aeruginosa bound to an inhibitor (yellow). The production of lipid A is essential for the growth and structural integrity of the cell membrane of Gram-negative bacteria. The outer membrane of Gram-negative bacteria makes them more resistant to antibiotics, therefore inhibition of LpxA is a drug target for treatment of these bacteria.