Frases Susana, Pontes Bruno, Nimrichter Leonardo, Rodrigues Marcio L, Viana Nathan B, Casadevall Arturo
Department of Microbiology and Immunology, Albert Einstein College of Medicine, The Bronx, New York, USA.
Biophys J. 2009 Aug 19;97(4):937-45. doi: 10.1016/j.bpj.2009.04.043.
Microbial capsules are important for virulence, but their architecture and physical properties are poorly understood. The human pathogenic fungus Cryptococcus neoformans has a large polysaccharide capsule that is necessary for virulence and is the target of protective antibody responses. To study the C. neoformans capsule we developed what we believe is a new approach whereby we probed the capsular elastic properties by applying forces using polystyrene beads manipulated with optical tweezers. This method allowed us to determine the Young's modulus for the capsule in various conditions that affect capsule growth. The results indicate that the Young's modulus of the capsule decreases with its size and increases with the Ca(2+) concentration in solution. Also, capsular polysaccharide manifests an unexpected affinity for polystyrene beads, a property that may function in attachment to host cells and environmental structures. Bead probing with optical tweezers provides a new, nondestructive method that may have wide applicability for studying the effects of growth conditions, immune components, and drugs on capsular properties.
微生物荚膜对毒力很重要，但其结构和物理性质却知之甚少。人类致病真菌新型隐球菌具有一个大型多糖荚膜，它对毒力至关重要，并且是保护性抗体反应的靶点。为了研究新型隐球菌荚膜，我们开发了一种我们认为是新的方法，即通过使用光镊操纵的聚苯乙烯珠子施加力来探测荚膜的弹性特性。这种方法使我们能够在影响荚膜生长的各种条件下确定荚膜的杨氏模量。结果表明，荚膜的杨氏模量随其大小而降低，并随溶液中Ca(2+)浓度的增加而增加。此外，荚膜多糖对聚苯乙烯珠子表现出意想不到的亲和力，这一特性可能在附着于宿主细胞和环境结构中发挥作用。用光镊进行珠子探测提供了一种新的、非破坏性的方法，可能在研究生长条件、免疫成分和药物对荚膜特性的影响方面具有广泛的适用性。
