Gram-negative bacterial outer membrane lipopolysaccharide (LPS) phosphate group (LPS phosphate group)

Gram-negative bacterial outer membrane lipopolysaccharide (LPS) phosphate groups are essential anionic moieties located on the Lipid A and core oligosaccharide sections of the LPS molecule (Raetz & Whitfield, 2002). These groups play a vital role in bacterial survival by binding divalent cations, such as magnesium and calcium, which cross-link adjacent LPS molecules to stabilize the outer membrane and form a robust permeability barrier (Clifton et al., 2015). This barrier protects the bacteria from environmental stressors and many conventional antibiotics (Nikaido, 2003). In clinical medicine, these phosphate groups are the primary targets for polymyxin antibiotics, such as Polymyxin B and Colistin, which utilize electrostatic attraction to bind the membrane (Trimpa et al., 2015). The resulting displacement of stabilizing cations leads to membrane disruption, increased permeability, and bactericidal activity (Yu et al., 2015). However, bacteria can develop resistance by modifying these phosphate groups with moieties like phosphoethanolamine or 4-amino-4-deoxy-L-arabinose, reducing the net negative charge and drug binding affinity (Baron et al., 2016).

Other names

Lipid A phosphate groupLPS phosphateLipopolysaccharide anionic siteLPS-P

Polymyxins bind to the negatively charged phosphate groups of Lipid A in the bacterial outer membrane via electrostatic interactions. This binding displaces divalent cations (Mg2+ and Ca2+) that normally stabilize the lipopolysaccharide layer, resulting in increased membrane permeability, leakage of cytoplasmic contents, and bacterial cell death (StatPearls, 2023; Nature Reviews Microbiology, 2019).