The pyruvate dehydrogenase complex as a cytoadhesin in Mycoplasma bovis that binds host extracellular matrix...

Adhesion and initial colonization are central determinants of pathogenesis in pathogenic mycoplasmas. Increasing evidence indicates that canonical metabolic enzymes can exhibit moonlighting functions. However, in Mycoplasma bovis, whether the key metabolic enzyme complex-pyruvate dehydrogenase complex (PDHc)-is surface exposed and directly mediates adhesion remains unsupported by whole-bacterial genetic evidence. Here, we systematically evaluate the surface localization, immunogenicity, and adhesive function of M. bovis PDHc (pdhA/B/C/D). PDHc subunits harbor conserved domains/motifs across diverse Mycoplasma species. pdhA/B/C/D in M. bovis are enriched at the cell membrane and detectable at the colony surface. PDHc is recognized by sera from naturally infected cattle and is expressed across clinical isolates. All four subunits bind specifically and in a dose-dependent manner to the membranes of embryonic bovine lung cells, thereby promoting cellular adhesion. The subunits exhibit distinct ligand preferences for extracellular matrix components. All four subunits bind to plasminogen, and pdhA additionally binds tissue-type plasminogen activator. At the bacterial level, M. bovisΔpdhB and M. bovisΔpdhC mutants exhibit remarkably reduced adhesion to embryonic bovine lung cells (p < 0.0001), which is restored upon complementation. Polyclonal antibodies against each subunit block the adhesion of M. bovis. These findings identify PDHc in M. bovis as a surface-exposed, multiligand adhesin complex that directly engages host factors. The conservation and immunogenicity of PDHc suggest promise for anti-adhesion interventions and subunit vaccine development.