L-type pyocins inhibit the BAM complex to kill without cell entry.

Abstract

Many antibiotics are ineffective against the Gram-negative pathogen Pseudomonas aeruginosa because of intrinsic defence mechanisms, such as the impermeable bacterial outer membrane. Here, we show that protein antibiotics called L-type pyocins kill P. aeruginosa by inhibiting the β-barrel assembly machinery (BAM) complex at the cell surface, halting outer-membrane protein assembly. Using single-particle cryo-electron microscopy, we show that L-type pyocins bind a surface-exposed region of BamA and deploy a C-terminal peptide that competitively inhibits the BAM complex, demonstrating that cell entry is not required for antibiotic activity. We combine genetics, multi-omics and cryo-electron tom..