The major MomP or PorA porin can exist as functional monomers and trimers; both exhibit ion conduction activity as well as the same cationic selectivity and sensitivity to low voltage (Dé et al. 2000; Bolla et al. 2004). It can transport polyarginine peptides (Dhanasekar et al. 2017). Nanobodies against MomP restrict Campylobacter colonization (Vanmarsenille et al. 2017). Healthy cats can carry C. jejuni of limited genetic diversity (Mohan and Habib 2019).