摘要

机会性病原体肺炎链球菌（肺炎球菌）利用自然遗传能力通过水平基因转移来增加其适应性。获得DNA的一种方法是通过用称为“细菌素”的抗菌肽捕获邻近菌株。肺炎球菌细菌素主要家族肺炎菌素的能力和产生分别由法定感应系统com和blp调节。在经典范例中，ABC转运蛋白ComAB和BlpAB各自分泌其自身系统的信号传导信号，并且在BlpAB的情况下也分泌肺炎球菌蛋白。尽管在所有肺炎球菌中发现了ComAB，但只有25％的菌株编码完整版本的BlpAB [BlpAB（+）]，而其余的不编码[BlpAB（ - ）]。与传统范式相反，之前已经表明BlpAB（ - ）菌株可以在短暂的能力期间通过ComAB介导的blp信息素分泌来激活blp。为了更好地了解COM-blp串扰的全部程度，我们检查了每个转运蛋白对能力发展和肺炎菌素分泌的贡献。我们发现BlpAB（+）菌株通过BlpAB介导的信息素分泌而具有更大的能力激活能力。同样，我们显示ComAB和BlpAB是混杂的，都可以分泌pneumocins。因此，BlpAB（+）和BlpAB（ - ）菌株之间的pneumocin分泌差异来自转运蛋白表达的调节和动力学，而不是底物特异性。我们推测BlpAB（ - ）菌株（机会主义者）主要使用肺炎菌素在精力充沛的情况下进行DNA获取和防御，而BlpAB（+）菌株（攻击者）扩大其对竞争菌株的一般抑制作用。

The opportunistic pathogen Streptococcus pneumoniae (pneumococcus) uses natural genetic competence to increase its adaptability through horizontal gene transfer. One method of acquiring DNA is through predation of neighboring strains with antimicrobial peptides called “bacteriocins.” Competence and production of the major family of pneumococcal bacteriocins, pneumocins, are regulated by the quorum-sensing systemscom and blp, respectively. In the classical paradigm, the ABC transporters ComAB and BlpAB each secretes its own system’s signaling pheromone and in the case of BlpAB also secretes the pneumocins. While ComAB is found in all pneumococci, only 25% of strains encode an intact version of BlpAB [BlpAB(+)] while the rest do not [BlpAB(−)]. Contrary to the classical paradigm, it was previously shown that BlpAB(−) strains can activate blpthrough ComAB-mediated secretion of the blp pheromone during brief periods of competence. To better understand the full extent of com-blp crosstalk, we examined the contribution of each transporter to competence development and pneumocin secretion. We found that BlpAB(+) strains have a greater capacity for competence activation through BlpAB-mediated secretion of the com pheromone. Similarly, we show that ComAB and BlpAB are promiscuous and both can secrete pneumocins. Consequently, differences in pneumocin secretion between BlpAB(+) and BlpAB(−) strains derive from the regulation and kinetics of transporter expression rather than substrate specificity. We speculate that BlpAB(−) strains (opportunists) use pneumocins mainly in a narrowly tailored role for DNA acquisition and defense during competence while BlpAB(+) strains (aggressors) expand their use for the general inhibition of rival strains.

http://www.pnas.org/content/early/2018/05/30/1804668115.short