Evidences of differential endoproteolytic processing on the surfaces of Mycoplasma hyopneumoniae and Mycoplasma flocculare.

Mycoplasma hyopneumoniae and Mycoplasma flocculare are genetic similar bacteria that colonize the swine respiratory tract. However, while M. hyopneumoniae is a pathogen that causes porcine enzootic pneumonia, M. flocculare is a commensal. Adhesion to the respiratory epithelium is mediated by surface-displayed adhesins, and at least some M. hyopneumoniae adhesins are post-translational proteolytically processed, producing differential proteoforms with differential adhesion properties. Based on LC-MS/MS data, we assessed differential proteolytic processing among orthologs of the five most abundant adhesins (p97 and p216) or adhesion-related surface proteins (DnaK, p46, and ABC transporter xylose-binding lipoprotein) from M. hyopneumoniae strains 7448 (pathogenic) and J (non-pathogenic), and M. flocculare. Both surface and cytoplasmic non-tryptic cleavage events were mapped and compared, and antigenicity predictions were performed for the resulting proteoforms. It was demonstrated that not only bona fide adhesins, but also adhesion-related proteins undergo proteolytical processing. Moreover, most of the detected cleavage events were differential among M. hyopneumoniae strains and M. flocculare, and also between cell surface and cytoplasm. Overall, our data provided evidences of a complex scenario of multiple antigenic proteoforms of adhesion-related proteins, that is differential among M. hyopneumoniae strains and M. flocculare, altering the surface architecture and likely contributing to virulence and pathogenicity.

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Declaration of competing interest The authors declare no conflict of interest.