Kjos Morten, Miller Eric, Slager Jelle, Lake Frank B, Gericke Oliver, Roberts Ian S, Rozen Daniel E, Veening Jan-Willem
Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Centre for Synthetic Biology, University of Groningen, Groningen, The Netherlands.
Institute of Biology, Leiden University, Leiden, the Netherlands.
PLoS Pathog. 2016 Feb 3;12(2):e1005422. doi: 10.1371/journal.ppat.1005422. eCollection 2016 Feb.
Pneumococcal bacteriocins (pneumocins) are antibacterial toxins that mediate intra-species competition within the human host. However, the triggers of pneumocin expression are poorly understood. Using RNA-sequencing, we mapped the regulon of the pneumocin cluster (blp) of Streptococcus pneumoniae D39. Furthermore, by analogy with pneumococcal competence, we show that several antibiotics activate the blp-genes. Using real-time gene expression measurements we show that while the promoter driving expression of the two-component regulatory system blpR/H is constitutive, the remaining blp-promoters that control pneumocin expression, immunity and the inducer peptide BlpC, are pH-dependent and induced in the late exponential phase. Intriguingly, competence for genetic transformation, mediated by the paralogous ComD/E two-component quorum system, is induced by the same environmental cues. To test for interplay between these regulatory systems, we quantified the regulatory response to the addition of synthetic BlpC and competence-stimulating peptide (CSP). Supporting the idea of such interplay, we found that immediately upon addition of CSP, the blp-promoters were activated in a comD/E-dependent manner. After a delay, blp-expression was highly induced and was strictly dependent on blpRH and blpC. This raised the question of the mechanism of BlpC export, since bioinformatic analysis showed that the genes encoding the putative exporter for BlpC, blpAB, are not intact in strain D39 and most other strains. By contrast, all sequenced pneumococcal strains contain intact comAB genes, encoding the transport system for CSP. Consistent with the idea that comAB mediate BlpC export, we finally show that high-level expression of the blp-genes requires comAB. Together, our results demonstrate that regulation of pneumocin expression is intertwined with competence, explaining why certain antibiotics induce blp-expression. Antibiotic-induced pneumocin expression might therefore have unpredictable consequences on pneumococcal colonization dynamics by activating genes that mediate intra-specific interference competition.
肺炎球菌细菌素（肺炎菌素）是介导人类宿主体内种内竞争的抗菌毒素。然而，肺炎菌素表达的触发因素却知之甚少。我们利用RNA测序技术绘制了肺炎链球菌D39肺炎菌素基因簇（blp）的调控子图谱。此外，通过与肺炎球菌感受态进行类比，我们发现几种抗生素可激活blp基因。利用实时基因表达测量技术，我们发现驱动双组分调控系统blpR/H表达的启动子是组成型的，而其余控制肺炎菌素表达、免疫及诱导肽BlpC的blp启动子则依赖于pH值，并在指数生长后期被诱导。有趣的是，由同源ComD/E双组分群体感应系统介导的遗传转化感受态，也由相同的环境信号诱导。为了测试这些调控系统之间的相互作用，我们对添加合成BlpC和感受态刺激肽（CSP）后的调控反应进行了定量分析。支持这种相互作用观点的是，我们发现加入CSP后，blp启动子立即以ComD/E依赖的方式被激活。延迟一段时间后，blp表达被高度诱导，且严格依赖于blpRH和blpC。这就提出了BlpC输出机制的问题，因为生物信息学分析表明，编码BlpC假定输出蛋白的基因blpAB在菌株D39和大多数其他菌株中并不完整。相比之下，所有已测序的肺炎球菌菌株都含有完整的comAB基因，该基因编码CSP的转运系统。与comAB介导BlpC输出的观点一致，我们最终表明blp基因的高水平表达需要comAB。总之，我们的结果表明肺炎菌素表达的调控与感受态相互交织，解释了为什么某些抗生素会诱导blp表达。因此，抗生素诱导的肺炎菌素表达可能会通过激活介导种内干扰竞争的基因，对肺炎球菌定植动态产生不可预测的影响。
