Gómez-Gómez José María, Amils Ricardo
Departamento de Virología y Microbiología, Laboratorio 104, Centro de Biología, Molecular Severo Ochoa, Campus of the Universidad, Autónoma de Madrid, C/ Nicolás Cabrera n° 1, Madrid 28049, Spain.
BMC Res Notes. 2014 Feb 25;7:108. doi: 10.1186/1756-0500-7-108.
Encased in a matrix of extracellular polymeric substances (EPS) composed of flagella, adhesins, amyloid fibers (curli), and exopolysaccharides (cellulose, β-1,6-N-acetyl-D-glucosamine polymer-PGA-, colanic acid), the bacteria Escherichia coli is able to attach to and colonize different types of biotic and abiotic surfaces forming biofilms and colonies of intricate morphological architectures. Many of the biological aspects that underlie the generation and development of these E. coli's formations are largely poorly understood.
Here, we report the characterization of a novel E. coli sessile behaviour termed "crowning" due to the bacterial generation of a new 3-D architectural pattern: a corona. This bacterial pattern is formed by joining bush-like multilayered "coronal flares or spikes" arranged in a ring, which self-organize through the growth, self-clumping and massive self-aggregation of cells tightly interacting inside semisolid agar on plastic surfaces. Remarkably, the corona's formation is developed independently of the adhesiveness of the major components of E. coli's EPS matrix, the function of chemotaxis sensory system, type 1 pili and the biofilm master regulator CsgD, but its formation is suppressed by flagella-driven motility and glucose. Intriguingly, this glucose effect on the corona development is not mediated by the classical catabolic repression system, the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex. Thus, corona formation departs from the canonical regulatory transcriptional core that controls biofilm formation in E. coli.
With this novel "crowning" activity, E. coli expands its repertoire of colonizing collective behaviours to explore, invade and exploit environments whose critical viscosities impede flagella driven-motility.
大肠杆菌包裹在由鞭毛、粘附素、淀粉样纤维（卷曲菌毛）和胞外多糖（纤维素、β-1,6-N-乙酰-D-葡糖胺聚合物-PGA-、柯氏酸）组成的细胞外聚合物（EPS）基质中，能够附着并定殖于不同类型的生物和非生物表面，形成具有复杂形态结构的生物膜和菌落。这些大肠杆菌结构的产生和发展背后的许多生物学方面在很大程度上仍未得到充分理解。
在此，我们报告了一种新型大肠杆菌固着行为的特征，因其产生了一种新的三维结构模式：冠状物，故而称为“加冕”。这种细菌模式是由排列成环的灌木状多层“冠状耀斑或尖峰”连接而成，它们通过在塑料表面的半固体琼脂内紧密相互作用的细胞的生长、自聚集和大量自我聚集而自组织形成。值得注意的是，冠状物的形成独立于大肠杆菌EPS基质主要成分的粘附性、趋化感觉系统的功能、1型菌毛和生物膜主调节因子CsgD，但它的形成受到鞭毛驱动的运动性和葡萄糖的抑制。有趣的是，这种葡萄糖对冠状物发育的影响不是由经典的分解代谢阻遏系统，即环腺苷酸（cAMP）-cAMP受体蛋白（CRP）复合物介导的。因此，冠状物的形成偏离了控制大肠杆菌生物膜形成的经典调控转录核心。
通过这种新型的“加冕”活动，大肠杆菌扩展了其定殖集体行为的范围，以探索、侵入和利用临界粘度阻碍鞭毛驱动运动性的环境。
