High resolution spatial order of physiological differentiation in structured biofilms of Escherichia coli

SERRA, DIEGO O.; RICHTER, ANJA M.; KLAUCK, GISELA; MIKA, FRANZISKA; HENGGE, REGINE

South Hadley, MA

Conferencia; Gordon Research Conference - Microbial stress response; 2012

Gordon Research Conference; Timothy Donohue & Susan Gottesman (Chairs).

Bacterial biofilms are multicellular structured communities, whose formation depends on motility and an extracellular matrix of adhesins, amyloid fibres and exopolysaccharides. Escherichia coli produces flagella during the post-exponential phase, when nutrients become limiting, but the rod-shaped cells still grow. Upon entry into stationary phase, cells stop producing flagella, become ovoid and multiple stress resistant and generate amyloid curli fibres. Using flagella, curli fibres and cell morphology as ´anatomical´ hallmarks in light, fluorescence and scanning electron microscopy, different physiological zones in macrocolony biofilms could be distinguished at high resolution. Small cells literally encased in a thick network of curli fibres form the outer biofilm layer. The inner zone is characterized by bistable curli expression. The bottom zone features larger cells and a tight mesh of entangled flagella, the formation of which requires flagellar motor function, suggesting a new role of flagella as an architectural element in biofilms. Cells in the outer rim growth zone produce flagella, which wrap around and tie cells together. In conclusion, our study reveals the microanatomy of a bacterial biofilm in unprecedented detail. It also shows bacterial curli networks to strikingly resemble Alzheimer plaques and it provides clues to understanding virulence of high curli-producing pathogenic E. coli.