Lipid II unlocked: strategies for obtaining a major antibiotic target.

Antimicrobial resistance (AMR) is a major global concern. It caused nearly five million deaths in 2019 and is projected to be responsible for up to ten million annually by 2050. A deeper understanding of how antibiotics interact with their molecular targets is essential to addressing this threat, as it can facilitate rational drug design. One major antibiotic target is lipid II, a highly conserved and essential precursor in bacterial cell wall biosynthesis. As the final monomeric intermediate in peptidoglycan biosynthesis, lipid II has become an important target for antibiotic discovery. However, accessing lipid II remains technically challenging. In this review, we examine the three main strategies used to obtain lipid II: direct extraction from bacteria, enzymatic or chemoenzymatic assembly using purified or partially purified biosynthetic machinery, and total chemical synthesis. We discuss the strengths and limitations of each method, scalability, and structural control, and highlight notable approaches that are expanding the accessibility of lipid II and its analogues. These advances are critical not only for antibiotic research but also for understanding bacterial physiology at the molecular level.