Breaking intrinsic antibiotic resistance. Outer membrane-permeabilizing peptides from innate bacterial proteomes.

Abstract

Intrinsic antibiotic resistance is the innate ability of bacteria to resist antimicrobial agents. The most defining structure that confers intrinsic antibiotic resistance, is the outer membrane of Gram-negative bacteria. It is a highly impermeable barrier that impedes various antibiotics from reaching their targets. A lot of research focuses on finding and developing novel drug candidates with increased antibacterial activity, but less research has been done on selective outer membrane permeabilization compounds. Such compounds could render Gram-negative bacteria susceptible to almost all known antimicrobials. It has been shown that the bacterial proteome is host to proteins containing a membrane-anchoring motif, which exerts selectivity towards the outer membrane. The aim of this Master thesis is to investigate the outer membrane permeabilizing properties of peptides derived from membrane-binding domains of innate peptides. This is realized through development and optimization of assays to assess the peptides outer and inner membrane activity against Escherichia coli. In addition, antibacterial activity was tested against both E. coli and the Gram-positive Bacillus subtilis. Here I show that 12 out of 14 innate peptides derived from E. coli and B. subtilis are active against the outer membrane of E. coli. Furthermore, FtsA10, MreB9, MurG12, FtsY11 from E. coli and MinD11 from B. subtilis are selective towards the outer membrane well below their growth inhibitory concentrations.