Varahan Sriram, Harms Nathan, Gilmore Michael S, Tomich John M, Hancock Lynn E
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, USA.
Division of Biology, Kansas State University, Manhattan, Kansas, USA.
mBio. 2014 Sep 23;5(5):e01726-14. doi: 10.1128/mBio.01726-14.
Enterococci are leading causes of hospital-acquired infection in the United States and continue to develop resistances to new antibiotics. Many Enterococcus faecalis isolates harbor pheromone-responsive plasmids that mediate horizontal transfer of even large blocks of chromosomal genes, resulting in hospital-adapted strains over a quarter of whose genomes consist of mobile elements. Pheromones to which the donor cells respond derive from lipoprotein signal peptides. Using a novel bacterial killing assay dependent on the presence of sex pheromones, we screened a transposon mutant library for functions that relate to the production and/or activity of the effector pheromone. Here we describe a previously uncharacterized, but well-conserved, ABC transporter that contributes to pheromone production. Using three distinct pheromone-dependent mating systems, we show that mutants defective in expressing this transporter display a 5- to 6-order-of-magnitude reduction in conjugation efficiency. In addition, we demonstrate that the ABC transporter mutant displays an altered biofilm architecture, with a significant reduction in biofilm biomass compared to that of its isogenic parent, suggesting that pheromone activity also influences biofilm development. The conservation of this peptide transporter across the Firmicutes suggests that it may also play an important role in cell-cell communication in other species within this important phylum.
Enterococcus faecalis ranks as one of the leading causes of hospital-associated infections. Strains possessing resistance to multiple antibiotics are becoming all too common in clinical settings. Pheromone-responsive plasmids play an important role in harboring and disseminating these antibiotic resistance genes. Here we have identified a novel ABC transporter that is responsible for the secretion of peptide pheromones, which enables communication between cells to mediate plasmid transfer. We have also shown that this transporter is important for biofilm formation, providing a strong rationale for its use as a viable therapeutic target which could be targeted to curb infection, as well as the spread of existing drug resistance.
肠球菌是美国医院获得性感染的主要病因，并且持续对新型抗生素产生耐药性。许多粪肠球菌分离株携带信息素响应质粒，这些质粒介导甚至大片段染色体基因的水平转移，导致医院适应性菌株，其基因组超过四分之一由可移动元件组成。供体细胞响应的信息素源自脂蛋白信号肽。我们使用一种依赖于性信息素存在的新型细菌杀伤试验，筛选转座子突变体文库以寻找与效应信息素的产生和/或活性相关的功能。在此，我们描述了一种先前未被表征但保守性良好的ABC转运蛋白，它有助于信息素的产生。使用三种不同的信息素依赖性交配系统，我们表明在表达这种转运蛋白方面存在缺陷的突变体在接合效率上降低了5到6个数量级。此外，我们证明ABC转运蛋白突变体显示出改变的生物膜结构，与其同基因亲本相比，生物膜生物量显著减少，这表明信息素活性也影响生物膜发育。这种肽转运蛋白在厚壁菌门中的保守性表明它可能在这个重要菌门的其他物种的细胞间通讯中也发挥重要作用。
粪肠球菌是医院相关感染的主要病因之一。对多种抗生素具有抗性的菌株在临床环境中变得越来越普遍。信息素响应质粒在携带和传播这些抗生素抗性基因方面发挥重要作用。在此，我们鉴定出一种新型ABC转运蛋白，它负责肽信息素的分泌，这使得细胞间能够通讯以介导质粒转移。我们还表明这种转运蛋白对生物膜形成很重要，为将其用作可行的治疗靶点提供了有力依据，该靶点可用于抑制感染以及现有耐药性的传播。
