Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
Appl Environ Microbiol. 2012 Apr;78(7):2282-8. doi: 10.1128/AEM.07618-11. Epub 2012 Jan 20.
Enterococcus faecalis, a commensal of the gastrointestinal tract and an opportunistic pathogen, has the ability to adhere to surfaces and form biofilms. It has been shown earlier that only 10 to 20% of an E. faecalis OG1RF culture expresses endocarditis- and biofilm-associated pili (Ebp), which are involved in biofilm formation. Another study revealed that E. faecalis clinical isolates, as well as OG1RF, are heterogeneous with respect to their apparent zeta potential, which was also correlated with increased ability to form biofilm. The aim of this study was to demonstrate that the heterogeneity in the presence of Ebp is correlated to that in apparent zeta potential. Heterogeneous cultures of OG1RF showed two distinct subpopulations with the most (-38 mV) and least (-26 mV) negative zeta potential. Deletion of EbpR, the activator of the ebp operon, or the structural genes ebpABC resulted in homogeneous culture with the most negative zeta potential. Conversely, overexpression of EbpR or the structural genes ebpABC resulted in homogeneous culture with the least negative zeta potential. The results show that ebp operon expression in E. faecalis, as measured by using P(ebp)-gfp promoter fusion, is the cause of heterogeneity in zeta potential and that pilus production causes the cells to behave as the least negative particle in an electric field.
粪肠球菌是胃肠道的共生菌和机会致病菌，具有黏附表面和形成生物膜的能力。早期的研究表明，只有 10%到 20%的粪肠球菌 OG1RF 培养物表达与心内膜炎和生物膜相关的菌毛（Ebp），这些菌毛参与生物膜的形成。另一项研究表明，粪肠球菌临床分离株以及 OG1RF 与明显的 ζ 电位具有异质性，这也与生物膜形成能力的增加有关。本研究旨在证明 Ebp 存在的异质性与明显 ζ 电位的异质性相关。OG1RF 的异质培养物显示出两种具有最负 ζ 电位（-38 mV）和最正 ζ 电位（-26 mV）的两个不同亚群。ebp 操纵子的激活子 ebpR 或结构基因 ebpABC 的缺失导致具有最负 ζ 电位的同质培养物。相反，ebpR 或结构基因 ebpABC 的过表达导致具有最负 ζ 电位的同质培养物。结果表明，使用 P(ebp)-gfp 启动子融合物测量的粪肠球菌中 ebp 操纵子的表达是 ζ 电位异质性的原因，菌毛的产生导致细胞在电场中表现为最负的粒子。
