In-situ, time-lapse study of extracellular polymeric substance discharge in Streptococcus mutans biofilm

Bernard Haochih Liu, Li Chieh Yu

研究成果: Article同行評審

11 引文 斯高帕斯(Scopus)

摘要

Streptococcus mutans is one of the main pathogens that cause tooth decay. By metabolizing carbohydrates, S. mutans emits extracellular polymeric substance (EPS) that adheres to the tooth surface and forms layers of biofilm. Periodontal disease occurs due to the low pH environment created by S. mutans biofilm, and such an acidic environment gradually erodes tooth enamel. Since the existence of EPS is essential in the formation of biofilm, the in-situ investigation of its generation and distribution in real time is the key to the control and suppression of S. mutans biofilm. Prior studies of the biofilm formation process by fluorescence microscope, scanning electron microscope, or spectroscope have roughly divided the mechanism into three stages: (1) initial attachment; (2) microcolonies; and (3) maturation. However, these analytical methods are incapable to observe real-time changes in different locations of the extracellular matrix, and to analyze mechanical properties for single bacteria in micro and nanoscale. Since atomic force microscopy (AFM) operates by precise control of tip-sample interaction forces in liquid and in air, living microorganisms can be analyzed under near-physiological conditions. Thus, analytical techniques based on AFM constitute powerful tools for the study of biological samples, both qualitatively and quantitatively. In this study, we used AFM to quantitatively track the changes of multiple nanomechanical properties of S. mutans, including dissipation energy, adhesion force, deformation, and elastic modulus at different metabolic stages. The data revealed that the bacterial extracellular matrix has a gradient distribution in stickiness, in which different stickiness indicates the variation of EPS compositions, freshness, and metabolic stages. In-situ, time-lapse AFM images showed the local generation and distribution of EPS at different times, in which the highest adhesion distributed along sides of the S. mutans cells. Through time-lapse analysis, we concluded that each contour layer is associated with a dynamic process of cell growth and nutrient consumption, and S. mutans is capable of controlling the priority of EPS secretion at specific locations. The live bacteria exhibited cyclic metabolic activities in the period of 23–34 min at the maturation stage of biofilm formation. In addition, the discharge of EPS is responsive to the shear stress caused by the topographical change of biofilm to provide stronger mechanical support in the formation of 3D networked biofilm.

原文English
頁(從 - 到)98-105
頁數8
期刊Colloids and Surfaces B: Biointerfaces
150
DOIs
出版狀態Published - 2017 二月 1

All Science Journal Classification (ASJC) codes

  • 生物技術
  • 表面和介面
  • 物理與理論化學
  • 膠體和表面化學

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