Lipopolysaccharide clustering in colistin persistent and resistant bacteria

Polymyxin antibiotics target lipopolysaccharides (LPS) in Gram-negative bacteria, but persistence and mcr-mediated resistance increasingly compromise their therapeutic efficacy. Here, we use super-resolution localisation microscopy to investigate the nanoscale organisation of LPS and membrane lipids in colistin-persistent Escherichia Pseudomonas aeruginosa. We find that persister cells exhibit heterogeneous LPS and membrane lipid distributions, with localised LPS clustering along the cell envelope, compared to susceptible cells. Unexpectedly, mcr-1-positive E. coli displays a similar LPS clustering phenotype to that of persisters, without altering membrane organisation. These findings suggest that both persistence and resistance involve envelope reorganisation, with increased LPS clustering and remodelling observed in both E. coli and P. aeruginosa. This work reveals a morphological signature of persistence and identifies a shared feature between persistence and resistance in Gram-negative bacteria.