Campycins are novel broad spectrum antibacterials killing Campylobacter jejuni by targeting the essential major outer membrane protein (MOMP)

Pyocins are high molecular weight bacteriocins produced by Pseudomonas aeruginosa that can be retargeted to new bacterial species by exchanging the pyocin tail fibers with bacteriophage receptor binding proteins (RBPs). Here, we develop retargeted pyocins called campycins as new antibacterials to specifically and effectively kill the major foodborne pathogen Campylobacter jejuni . We used two diverse RBPs (H-fibers) encoded by CJIE1 prophages found in the genomes of C. jejuni strains CAMSA2147 and RM1221 to construct Campycin 1 and Campycin 2, respectively. Together Campycin 1 and 2 could target all C. jejuni strains tested due to complementary antibacterial spectrums. In addition, both campycins led to more than 3 log reductions in C. jejuni counts under microaerobic conditions at 42°C, whereas the killing efficiency was less efficient under anaerobic conditions at 5°C. We furthermore discovered that both H-fibers used to construct the campycins bind to the essential major outer membrane protein (MOMP) present in all C. jejuni , in a strain specific manner. Protein sequence alignment and structural modelling suggest that the highly variable extracellular loops of MOMP form the binding sites of the diverse H-fibers. Further in silico analyses of 5000 MOMP sequences suggest that the protein fall into three major clades predicted to be targeted by either Campycin 1 or Campycin 2. Thus, campycins are promising antibacterials against C. jejuni expected to broadly target numerous strains of this human pathogen found in nature and agriculture.