外源糖原调控猪链球菌基因表达的转录组分析

Transcriptome analysis of exogenous glycogen availability regulating gene expression of Streptococcus suis

【背景】碳水化合物的利用与猪链球菌在宿主体内的定殖和致病性密切相关。感染期间,宿主细胞释放的糖原可能是猪链球菌重要的碳源。【目的】从转录组学角度解析猪链球菌全基因转录水平对外源糖原诱导的响应,特别是毒力基因。【方法】将猪链球菌2型强毒株分别用糖原和葡萄糖进行液体培养,通过高通量转录组测序,比较分析糖原对猪链球菌代谢通路和毒力基因差异表达的影响,并通过体外试验和攻毒试验进行验证。【结果】猪链球菌在糖原培养基中生长良好。转录组数据显示,糖原培养条件下的猪链球菌共有908个基因差异表达,基因组占比46.07%,其中501个基因上调表达,407个基因下调表达。富集分析结果表明,糖原影响了猪链球菌广泛的基础代谢过程,但糖酵解途径保持稳定。30个毒力基因的表达水平发生变化,重要的毒力因子SLY、ApuA、ArcABC等的基因转录水平大幅度升高(倍数>20)。糖原培养后的猪链球菌的溶血活性、黏附和侵入能力显著上升,对受试动物的毒力增强,证实猪链球菌能够响应糖原诱导,糖原能调控猪链球菌的致病性。【结论】外源糖原的利用显著影响了猪链球菌的基因表达谱,这种对碳源的响应是细菌对不断变化的生存环境的适应性,也反映了细菌对碳水化合物的利用与其致病性之间的紧密联系。

[Background]Carbohydrate is closely related to the colonization and pathogenicity of Streptococcus suis in hosts,and the glycogen released from host cells may be an important carbon source of S.suis.[Objective]This paper aims to analyze the effect of exogenous glycogen on the transcriptome response of S.suis,especially the virulence genes.[Methods]The virulent S.suis type 2 SC19 strain was cultured in the glycogen and glucose medium,respectively.Through high-throughput transcriptome sequencing,the effect of glycogen on the metabolic pathways and virulence genes of S.suis were identified and analyzed,followed by verification through in vitro experiment and challenge test.[Results]S.suis grew well in the medium containing glycogen as the carbon source.Transcriptome data showed 908(46.07%of the whole genome)differentially expressed genes under the glycogen culture condition,with 501 up-regulated and 407 down-regulated.Enrichment analysis revealed that glycogen affected a wide range of basic metabolic pathways in S.suis,but the glycolysis pathway remained stable.The expression levels of 30 virulence genes significantly changed.In particular,a series of known and important virulence factors,such as SLY,ApuA,and ArcABC,were highly up-regulated(fold change>20).Moreover,results showed that the hemolytic activity,adhesion,and invasion of S.suis cultured in glycogen significantly enhanced,and that its virulence to the tested animal model predictably increased.Thus,it was confirmed that S.suis responded to glycogen and glycogen regulated the pathogenicity of S.suis.[Conclusion]Exogenous glycogen significantly affected the genome expression profile of S.suis.Such response to the carbon source suggests the adaptability of the bacteria to the changing habitats and the close relationship between the carbohydrate and S.suis pathogenicity.