Characterization of the Porins of Campylobacter jejuni and Campylobacter coli and Implications for Antibiotic Susceptibility WILLIAM J. PAGE,1'* GREGORY HUYER,1 MARIANNE HUYER,1 AND ELIZABETH A. WOROBEC2 Department of Microbiology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9,' and Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N22 Received 25 August 1988/Accepted 25 November 1988
The major outer membrane protein was extracted from Campylobacter coli by Triton X-100/EDTA fractionation of cell envelopes. This heat-modifiable protein was shown to have pore-forming activity in black lipid bilayers. The C. coli porin formed a relatively small cation-selective pore with a mean single-channel conductance of 0.53 + 0.16 nS in 1.0 M KCI. There was no evidence of oligomer formation, which suggested that each protein monomer formed a pore. Pore-forming activity of the C. coli porin and similarly prepared Campylobacterjejuni porin was also measured in liposome-sweiling assays. These results confirmed the cation selectivity of both pores. The C. coli porin formed a small pore, which hindered the penetration of solutes with a molecular weight of 262, and a larger pore, which hindered the penetration of solutes with a molecular weight of 340, in a protein-concentration-dependent manner. C. jejuni formed one size of pore that was slightly larger than the C. coli pore and just permitted the passage of solutes, with a molecular weight of 340. A review of the literature concerning in vitro screening of antimicrobial agents tended to confirm the low permeability of the C. jejuni outer membrane to hydrophilic antimicrobial agents except when the molecules had molecular weights of
