Ran S J, Jiang W, Zhu C L, Liang J P
Department of Endodontics and Operative Dentistry, Shanghai Key Laboratory of Stomatology, Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
Shanghai Research Institute of Stomatology, Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
Aust Dent J. 2015 Jun;60(2):143-53. doi: 10.1111/adj.12324. Epub 2015 May 20.
Enterococcus faecalis is the most common single species present in teeth after failed root canal therapy. This is mainly due to its ability to maintain viability for a long time in filled root canals where nutrients are normally sparse. The aim of this study was to explore the mechanism of E. faecalis survival and biofilm formation in glucose-starved environments.
Enterococcus faecalis ATCC 33186 was inoculated in energy starvation media for biofilm formation. Confocal laser scanning microscopy and fluorescent DNA-binding agents were employed to assess biofilm-forming ability. The physiochemical properties of the biofilm cell wall were investigated by measuring the hydrophobicity, extracellular polysaccharide and ATPase activity. The expression of stress and virulence genes was quantified by real-time quantitative polymerase chain reaction.
The ability for biofilm formation decreased with a decreasing concentration of glucose. The cell surface hydrophobicity increased dramatically with decreasing glucose concentration. Water-soluble exopolysaccharide (WSE) synthesis decreased in glucose starvation media, whereas water-insoluble exopolysaccharide (WIE) synthesis increased. A marked decrease in ATPase activity was observed only in a no glucose medium. In addition, transcription of ace, fsrB and gelE genes increased under glucose starvation stress while atpE, salB and esp genes were down-regulated.
Enterococcus faecalis survival and biofilm formation under glucose starvation stress may be attributed to an increase in cell-surface hydrophobicity and additionally to the up-regulation of some genes involved in stress response and biofilm formation. These characteristics may explain why E. faecalis can maintain viability for a long time in an energy-starved environment and why it is frequently isolated from persistently infected root canals.
粪肠球菌是根管治疗失败后牙齿中最常见的单一菌种。这主要归因于其在营养通常稀少的充填根管中长时间维持生存能力的能力。本研究的目的是探讨粪肠球菌在葡萄糖饥饿环境中存活及形成生物膜的机制。
将粪肠球菌ATCC 33186接种于能量饥饿培养基中以形成生物膜。采用共聚焦激光扫描显微镜和荧光DNA结合剂评估生物膜形成能力。通过测量疏水性、细胞外多糖和ATP酶活性来研究生物膜细胞壁的理化性质。通过实时定量聚合酶链反应对应激和毒力基因的表达进行定量。
生物膜形成能力随葡萄糖浓度降低而下降。细胞表面疏水性随葡萄糖浓度降低而显著增加。在葡萄糖饥饿培养基中，水溶性胞外多糖（WSE）合成减少，而水不溶性胞外多糖（WIE）合成增加。仅在无葡萄糖培养基中观察到ATP酶活性显著下降。此外，在葡萄糖饥饿应激下，ace、fsrB和gelE基因的转录增加，而atpE、salB和esp基因下调。
粪肠球菌在葡萄糖饥饿应激下的存活及生物膜形成可能归因于细胞表面疏水性增加，以及一些参与应激反应和生物膜形成的基因上调。这些特性可能解释了粪肠球菌为何能在能量饥饿环境中长时间维持生存能力，以及为何它经常从持续感染的根管中分离出来。
