Effect of Tran on virulence through regulating metabolism and stress tolerance of Streptococcus suis serotype 2

Streptococcus suis (SS) is an important zoonotic pathogen causing a variety of life-threatening infections in pigs and humans. Tran, a novel transcriptional regulator which was identified to be an infection-related factor in S. suis serotype 2 using suppression subtractive hybridization (SSH), has been reported by our group. In this study, a tran deletion mutant was constructed to compare with the wild-type ZY05719 in some biological characteristics. It is suggested that longer chains and relatively slower growth could be observed in tran deletion mutants. In order to identify gene transcription profiles, microarray analysis was performed. It indicated that the inactivation of Tran led to 130 differentially expressed genes spread throughout the genome. Among these, 21 genes were upregulated, and 109 genes were downregulated. Most of the differentially expressed genes were involved in bacterial metabolism, such as the phosphotransferase system (PTS), and heat shock proteins. In the case of glucose scarcity, the growth characteristics of tran deletion mutants were impacted significantly, meanwhile Δtran mutant was highly sensitive to environmental stresses. Moreover, cell adherence decreased by 22.2%, and virulence in zebrafish declined to more than five times in Δtran mutants. These data demonstrate the role of Tran in regulation in S. suis serotype 2, that is affect bacterial virulence by influencing bacterial metabolism and stress tolerance of external environment.