Proteomic Characterisation of Two Strains of Mycoplasma mycoides Subsp. Mycoides of Differing Pathogenicity

Abstract

Mycoplasma mycoides subsp mycoides (Mmm) is a major pathogen of cattle, causing contagious bovine pleuropneumonia (CBPP), a severe–frequently fatal-disease that is widespread in sub-tropical countries. Despite recognition as a pathogen in the 19th century and advances made through genome sequencing and synthetic biology, many of the molecular characteristics of Mmm remain poorly characterized. Using a proteomics approach, this study aimed to define Mmm major protein determinants, including surface membrane proteins and those involved in host colonization and pathogenicity. For this purpose, both whole cells and a Triton X-114 enriched membrane fraction of a highly pathogenic African field strain (N6) and a vaccine strain (KH3J) were analysed and compared using gel based methodologies i.e. 2-DGE and SDS-PAGE in combination with MALDI-MS/MS and LC-ESI-MS/MS. A total of 318 proteins, (around 31% of the predicted proteome) were identified, comprising lipoproteins, prolipoproteins and hypothetical proteins with predicted membrane locations and possible roles in pathogenicity. One hundred and forty-five of these proteins, with different predicted sub-cellular locations and functions but also including uncharacterized proteins, have not previously been reported as expressed by Mmm. Many more proteins were detected by LC-ESI-MS/MS (n=315) than by 2-DGE and MALDI-MS/MS (n=52), however 3 proteins were detected only by the latter approach. Most proteins were observed to be common to both strains although a substantial number of proteins were detected exclusively in only one strain with possible implications for fitness and pathogenicity. To our knowledge, this study represents the most extensive proteomics characterization of Mmm to date and has identified characteristics on which to base future studies of the physiology and pathogenicity of this prokaryote.