To investigate the influence of STP and STK on protein expression in S. suis, we performed a comparative proteomics analysis with the WT, Δstp, and Δstk strains using liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS).STK and STP are serine/threonine kinases and phosphatases, respectively. Therefore, we next analyzed the changes in the abundance of serine/threonine phosphorylated proteins in Δstp and Δstk compared with the WT strain.