Layered Structure and Complex Mechanochemistry Underlie Strength and Versatility in a Bacterial Adhesive.
Layered Structure and Complex Mechanochemistry Underlie Strength and Versatility in a Bacterial Adhesive.
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层状结构和复杂的机械化学是细菌粘合剂强度和多功能性的基础。
DOI：
10.1128/mbio.02359-17
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发表时间：
2018-02-06
期刊：
影响因子：
6.4
通讯作者：
Berne C
中科院分区：
文献类型：
--
作者：
Hernando-Pérez M;Setayeshgar S;Hou Y;Temam R;Brun YV;Dragnea B;Berne C
虽然设计在水环境中使用的合成粘合剂具有挑战性，但微生物通常会产生生物粘合剂，可以有效地附着在各种基质上，包括湿表面。水生细菌新月形茎杆菌使用一种分离的多糖复合物，即固化剂，强烈地附着在表面并抵抗流动。这种支架用途非常广泛，并且具有令人印象深刻的粘接强度。在这里，我们使用原子力显微镜结合超分辨率显微镜和酶分析来解开固定物的复杂结构，并表征其化学成分及其在粘附中的作用。我们的数据支持一个模型，即支架是由两层组成的异质材料：一个更硬的纳米级核心层包裹在一个稀疏的、深远的、灵活的刷层中。此外，我们发现，在表面接触后，持石的弹性响应从最初的非均匀发展到更均匀。从组成的角度来看，除了n -乙酰-d-氨基葡萄糖（NAG），我们的数据表明，目前唯一已确定的成分，持铁含有肽和DNA。我们假设，虽然多肽是最重要的粘附力成分，但DNA的存在主要影响刷层和初始粘附强度，NAG在核心内起主要的结构作用。其结构和组成的复杂性可能是其作为湿粘合剂的多功能性和独特强度的基础。对这种生物粘合剂的机械化学理解的持续改进可以为细菌如何附着在表面提供新的见解，并可以为新粘合剂的开发提供信息。迫切需要一种能在水下发挥作用的强效、生物相容性的生物胶粘剂。为了牢固地附着在表面上并抵抗水下的水流，新月形茎杆菌产生了一种被称为固化剂的粘合剂，其机械化学性质尚不清楚。研究结果表明，该结构为层状结构，具有刚性核心层和聚合物刷层，由多糖、多肽和DNA组成。DNA似乎在刷层结构和初始粘附中起作用，肽在粘附强度中起作用，多糖在核心结构中起作用。这里所描述的复杂、多层的组织结构和多样的化学性质构成了这种固定物独特的粘附特性的基础，并将为细菌粘附和生物粘附应用的机制提供重要的见解。
While designing synthetic adhesives that perform in aqueous environments has proven challenging, microorganisms commonly produce bioadhesives that efficiently attach to a variety of substrates, including wet surfaces. The aquatic bacterium Caulobacter crescentus uses a discrete polysaccharide complex, the holdfast, to strongly attach to surfaces and resist flow. The holdfast is extremely versatile and has impressive adhesive strength. Here, we used atomic force microscopy in conjunction with superresolution microscopy and enzymatic assays to unravel the complex structure of the holdfast and to characterize its chemical constituents and their role in adhesion. Our data support a model whereby the holdfast is a heterogeneous material organized as two layers: a stiffer nanoscopic core layer wrapped into a sparse, far-reaching, flexible brush layer. Moreover, we found that the elastic response of the holdfast evolves after surface contact from initially heterogeneous to more homogeneous. From a composition point of view, besides N-acetyl-d-glucosamine (NAG), the only component that had been identified to date, our data show that the holdfast contains peptides and DNA. We hypothesize that, while polypeptides are the most important components for adhesive force, the presence of DNA mainly impacts the brush layer and the strength of initial adhesion, with NAG playing a primarily structural role within the core. The unanticipated complexity of both the structure and composition of the holdfast likely underlies its versatility as a wet adhesive and its distinctive strength. Continued improvements in understanding of the mechanochemistry of this bioadhesive could provide new insights into how bacteria attach to surfaces and could inform the development of new adhesives. There is an urgent need for strong, biocompatible bioadhesives that perform underwater. To strongly adhere to surfaces and resist flow underwater, the bacterium Caulobacter crescentus produces an adhesive called the holdfast, the mechanochemistry of which remains undefined. We show that the holdfast is a layered structure with a stiff core layer and a polymeric brush layer and consists of polysaccharides, polypeptides, and DNA. The DNA appears to play a role in the structure of the brush layer and initial adhesion, the peptides in adhesive strength, and the polysaccharides in the structure of the core. The complex, multilayer organization and diverse chemistry described here underlie the distinctive adhesive properties of the holdfast and will provide important insights into the mechanisms of bacterial adhesion and bioadhesive applications.