A Quorum-Sensing System That Regulates Streptococcus pneumoniae Biofilm Formation and Surface Polysaccharide Production.
A Quorum-Sensing System That Regulates Streptococcus pneumoniae Biofilm Formation and Surface Polysaccharide Production.
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DOI：
10.1128/msphere.00324-17
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发表时间：
2017-09
期刊：
影响因子：
4.8
通讯作者：
Petersen FC
中科院分区：
文献类型：
--
作者：
Junges R;Salvadori G;Shekhar S;Åmdal HA;Periselneris JN;Chen T;Brown JS;Petersen FC
群体感应通过信息素的产生、分泌和感应来调节细菌的社会行为。在这项研究中，我们在肺炎链球菌D39中鉴定了一种新的RGG/SHP类群体感应系统。该系统被发现直接诱导单个基因簇的表达，该基因簇包括SHP信息素基因和在胶囊合成中可能具有功能的基因。通过葡聚糖排除法测量的胶囊大小，在R36A中暴露于SHP可以增加，R36A是D39的一种非囊化衍生物。在被包裹的亲本菌株中，基因簇的过表达增加了衣壳的大小，支持了RGG/SHP在表面多糖合成中的作用。此外，我们发现该系统的过度表达减少了上皮细胞上生物膜的形成，而在RGG缺失的突变体中则增加了生物膜的形成。将表面多糖的表达置于群体感应调节下，可能使肺炎链球菌能够根据环境和细胞密度条件调整与宿主和其他细菌的相互作用。尽管接种了疫苗，肺炎链球菌每年仍导致100多万人死亡。因此，了解肺炎球菌如何从共生菌转变为病原体特别重要。群体感应调节集体行为，因此代表了共生向病原体转变的潜在驱动因素。RGG/小疏水性多肽(SHP)群体感应系统在链球菌中广泛存在，但在肺炎链球菌中仍基本不具特征。利用定向转录组测序，我们发现肺炎链球菌D39 Rgg0939/SHP系统诱导了包括shp和衣壳基因同源物在内的单基因簇的转录。通过荧光素异硫氰酸酯-葡聚糖排除法测定胶囊大小，可以将该系统指定为调节表面多糖表达的系统。我们发现SHP信息素诱导了R36A胞外多糖的表达，R36A是D39的一个未包裹的衍生物。在被包裹的亲本菌株中，RGG系统的过表达导致突变体的被膜大小增加。与先前表明被膜表达与生物膜形成相反相关的研究一致，我们发现肺上皮细胞上形成的生物膜在过度表达菌株中减少，在RGG缺失突变体中增加。虽然在肺部感染的小鼠模型中，D39和RGG缺失突变体之间没有显著差异，但在竞争性测试中，过度表达降低了适应性。这是首次在链球菌中发现一种群体感应系统，该系统从不同于原始被膜位置的位置调节胞外多糖的合成。重要群体感应通过信息素的产生、分泌和感应来调节细菌的社会行为。在这项研究中，我们在肺炎链球菌D39中鉴定了一种新的RGG/SHP类群体感应系统。该系统被发现直接诱导单个基因簇的表达，该基因簇包括SHP信息素基因和在胶囊合成中可能具有功能的基因。通过葡聚糖排除法测量的胶囊大小，在R36A中暴露于SHP可以增加，R36A是D39的一种非囊化衍生物。在被包裹的亲本菌株中，基因簇的过表达增加了衣壳的大小，支持了RGG/SHP在表面多糖合成中的作用。此外，我们发现该系统的过度表达减少了上皮细胞上生物膜的形成，而在RGG缺失的突变体中则增加了生物膜的形成。将表面多糖的表达置于群体感应调节下，可能使肺炎链球菌能够根据环境和细胞密度条件调整与宿主和其他细菌的相互作用。
Quorum sensing regulates bacterial social behaviors by production, secretion, and sensing of pheromones. In this study, we characterized a new quorum-sensing system of the Rgg/SHP class in S. pneumoniae D39. The system was found to directly induce the expression of a single gene cluster comprising the gene for the SHP pheromone and genes with putative functions in capsule synthesis. Capsule size, as measured by dextran exclusion, was increased by SHP exposure in R36A, an unencapsulated derivative of D39. In the encapsulated parent strain, overexpression of the gene cluster increased capsule size, supporting the role of Rgg/SHP in the synthesis of surface polysaccharides. Further, we found that biofilm formation on epithelial cells was reduced by overexpression of the system and increased in a mutant with an rgg deletion. Placing surface polysaccharide expression under quorum-sensing regulation may enable S. pneumoniae to tune interactions with the host and other bacteria in accordance with environmental and cell density conditions. Despite vaccines, Streptococcus pneumoniae kills more than a million people yearly. Thus, understanding how pneumococci transition from commensals to pathogens is particularly relevant. Quorum sensing regulates collective behaviors and thus represents a potential driver of commensal-to-pathogen transitions. Rgg/small hydrophobic peptide (SHP) quorum-sensing systems are widespread in streptococci, yet they remain largely uncharacterized in S. pneumoniae. Using directional transcriptome sequencing, we show that the S. pneumoniae D39 Rgg0939/SHP system induces the transcription of a single gene cluster including shp and capsule gene homologs. Capsule size measurements determined by fluorescein isothiocyanate-dextran exclusion allowed assignment of the system to the regulation of surface polysaccharide expression. We found that the SHP pheromone induced exopolysaccharide expression in R36A, an unencapsulated derivative of D39. In the encapsulated parent strain, overexpression of the Rgg system resulted in a mutant with increased capsule size. In line with previous studies showing that capsule expression is inversely associated with biofilm formation, we found that biofilm formed on lung epithelial cells was decreased in the overexpression strain and increased in an rgg deletion mutant. Although no significant differences were observed between D39 and the rgg deletion mutant in a mouse model of lung infection, in competitive assays, overexpression reduced fitness. This is the first study to reveal a quorum-sensing system in streptococci that regulates exopolysaccharide synthesis from a site distinct from the original capsule locus. IMPORTANCE Quorum sensing regulates bacterial social behaviors by production, secretion, and sensing of pheromones. In this study, we characterized a new quorum-sensing system of the Rgg/SHP class in S. pneumoniae D39. The system was found to directly induce the expression of a single gene cluster comprising the gene for the SHP pheromone and genes with putative functions in capsule synthesis. Capsule size, as measured by dextran exclusion, was increased by SHP exposure in R36A, an unencapsulated derivative of D39. In the encapsulated parent strain, overexpression of the gene cluster increased capsule size, supporting the role of Rgg/SHP in the synthesis of surface polysaccharides. Further, we found that biofilm formation on epithelial cells was reduced by overexpression of the system and increased in a mutant with an rgg deletion. Placing surface polysaccharide expression under quorum-sensing regulation may enable S. pneumoniae to tune interactions with the host and other bacteria in accordance with environmental and cell density conditions.