Screening of Virulence-Related Transcriptional Regulators in <i>Streptococcus suis</i>

• Main Authors: Liang Liu, Qiang Zhang, Zhongmin Xu, Bo Chen, Anding Zhang, Xiaomei Sun, Meilin Jin
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Genes
• Subjects: <i>Streptococcus suis</i>; transcriptional regulator; in vivo; virulence; mutant
• Online Access: https://www.mdpi.com/2073-4425/11/9/972

<i>Streptococcus suis</i> (<i>S.suis</i>) is an important zoonotic pathogen that causes many severe diseases in pigs and humans. Virulence-related transcriptional regulators have been widely reported in pathogenic microorganisms, but only a few have been identified in <i>S.suis</i>. Our aim was to screen virulence-related transcriptional regulators in <i>S.suis</i>. A total of 89 such genes were predicted in the <i>S.suis</i> genome, of which 22 were up-regulated and 18 were down-regulated during <i>S.suis</i> infection in mice. To evaluate the roles of these differentially expressed factors in <i>S.suis</i> virulence, deletion mutants were constructed, and 10 mutants were successfully obtained. Among these genes, the deletion of <i>comR</i>, <i>sitR</i>, or <i>sxvR</i> caused significantly decreased virulence in mice, compared to that with the wild-type strain. Moreover, the survival of Δ<i>comR</i>, Δ<i>sitR</i>, and Δ<i>sxvR</i> mutant strains in blood was significantly reduced both in vitro and in vivo. Furthermore, their pro-inflammatory abilities were also obviously decreased in vivo. The regulatory mechanisms of <i>comR</i>, <i>sitR</i>, and <i>sxvR</i> were then analyzed by whole transcriptome RNA sequencing (RNA-Seq). Results indicated that the absence of <i>comR</i> induced the down-regulation of 17 virulence factors or virulence-related factors, including genes involved in the synthesis of capsules, oxidative stress tolerance, immune evasion, and cell division. Furthermore, three and two virulence factors or virulence-related factors were down-regulated upon deletion of <i>sitR</i> and <i>sxvR</i>, respectively. Thus, this study reports the discovery of three virulence-associated transcriptional regulatory factors in <i>S.suis</i>. These factors could ultimately be targeted to control infection caused by these bacteria.