The Eukaryote-Like Serine/Threonine Kinase STK Regulates the Growth and Metabolism of Zoonotic Streptococcus suis

Abstract

Like eukaryotes, bacteria express one or more serine/threonine kinases (STKs) that initiate diverse signaling networks. The STK from <i>Streptococcus suis</i> is encoded by a single-copy <i>stk</i> gene, which is crucial in stress response and virulence. To further understand the regulatory mechanism of STK in <i>S. suis</i>, a <i>stk</i> deletion strain (Δ<i>stk</i>) and its complementary strain (CΔ<i>stk</i>) were constructed to systematically decode STK characteristics by applying whole transcriptome RNA sequencing (RNA-Seq) and phosphoproteomic analysis. Numerous genes were differentially expressed in Δ<i>stk</i> compared with the wild-type parental strain SC-19, including 320 up-regulated and 219 down-regulated genes. Particularly, 32 virulence-associated genes (VAGs) were significantly down-regulated in Δ<i>stk</i>. Seven metabolic pathways relevant to bacterial central metabolism and translation are significantly repressed in Δ<i>stk</i>. Phosphoproteomic analysis further identified 12 phosphoproteins that exhibit differential phosphorylation in Δ<i>stk</i>. These proteins are associated with cell growth and division, glycolysis, and translation. Consistently, phenotypic assays confirmed that the Δ<i>stk</i> strain displayed deficient growth and attenuated pathogenicity. Thus, STK is a central regulator that plays an important role in cell growth and division, as well as <i>S. suis</i> metabolism.