Mechanisms Involved in Bacterial Cellulose Biosynthesis

大肠杆菌和沙门氏菌形成高度耐药的生物膜，由纤维素和卷曲菌毛组成，帮助这些细菌逃避免疫系统的检测，并增加它们对抗菌剂和恶劣环境因素的耐受性。纤维素成分特别提供保护，免受机械、化学和生物压力，并促进对多种表面的粘附性，如上皮细胞、各种食品、供水系统等。因此，了解生物膜的形成和组成对于了解这些细菌如何在环境水库中站稳脚跟，从而使它们能够继续威胁我们的食品/水安全、工业过程和一般健康至关重要。细菌纤维素还具有生物工程意义，因为它具有独特的物理/化学性质，与藻类或植物来源的纤维素相比具有显著的优势。这些特性已经被成功地用于产生新型伤口敷料、生物塑料、生物燃料和用于组织再生的生物惰性载体。尽管细菌纤维素的生物学和工业意义正在扩大，但人们对细菌合成和输出这种聚合物知之甚少。遗传学研究已经证明，bcsABZCEFG这七个基因对肠道细菌中纤维素的生物合成是必不可少的。我们假设，BCS蛋白聚集在一起，形成一个跨越细菌细胞壁的复合体，促进细胞内纤维素的协调聚合、输出和释放。使用大肠杆菌作为模型系统，我们的目标是利用多学科方法来表征这些过程中涉及的每一种蛋白质的结构和功能。这项研究的结果将是揭示绕过生物膜屏障的独特方法的关键，并将为设计具有特定性能的医疗/工业应用的聚合物(或酶)奠定基础。同样重要的是，对纤维素合成/输出的详细了解将有助于发现与细菌物种间的多糖合成和生物膜发展有关的重要原理。

Escherichia and Salmonella species form highly resistant biofilms, composed of cellulose and curli fimbriae, that helps these bacteria elude detection by the immune system and increases their tolerance to antimicrobial agents and harsh environmental factors. The cellulose component specifically confers protection from mechanical, chemical and biological stresses and promotes adherence to a number of surfaces, such as epithelial cells, a variety of foods, water distribution systems and more. Thus, knowledge of biofilm formation and composition is of critical importance to understanding how these bacteria establish themselves in environmental reservoirs, thereby enabling them to continue to threaten our food/water security, industrial processes and general health. Bacterial cellulose is also gaining bioengineering significance as it has unique physical/chemical properties that provide significant advantages when compared to algal or plant derived cellulose. These properties have been successfully exploited for the generation of novel wound dressings, bio-plastics, biofuels and bio-inert supports for tissue regeneration. Even though the biological and industrial implications of bacterial cellulose are expanding, little is known about the synthesis and export of this polymer by bacteria. Genetic studies have demonstrated that seven genes, bcsABZCEFG, are essential for the biosynthesis of cellulose in Enteric bacteria. We hypothesize that the Bcs proteins come together to form a bacterial cell wall spanning complex that facilitates the coordinated polymerization, export and release of cellulose from the cell. Using E. coli as a model system, our goals are to utilize a multidisciplinary approach to characterize the structure and function of each of the proteins involved in these processes. The results of this research will be key to revealing unique approaches to circumvent the biofilm barrier and will and lay the groundwork for designing polymers (or enzymes) with specific properties for medical/industrial applications. Equally important, a detailed understanding of the synthesis/export of cellulose will lead to the discovery of important principles relating to polysaccharide synthesis and biofilm development across bacterial species.