An ultrasensitive microfluidic approach reveals correlations between the physico-chemical and biological activity of experimental peptide antibiotics
Antimicrobial resistance challenges the ability of modern medicine to contain infections. Given the dire need for new antimicrobials, peptide antibiotics hold particular promise. These agents hit multiple targets in bacteria starting with their most exposed regions - their membranes. However, suitable assays to quantify the efficacy of peptide antibiotics at the membrane and cellular level have been lacking. Here, we employ two complementary microfluidic platforms to probe the structure-activity relationships of two experimental series of peptide antibiotics. We reveal strong correlations between each peptides physicochemical activity at the membrane level and biological activity at the cellular level by assaying the membranolytic activities of the antibiotics on hundreds of individual giant lipid vesicles, and quantifying phenotypic responses within clonal bacterial populations with single-cell resolution. Our strategy proved capable of detecting differential responses for peptides with single amino acid substitutions between them, and can accelerate the rational design and development of peptide antimicrobials.