Influence of type I fimbriae and fluid shear stress on bacterial behavior and multicellular architecture of early Escherichia coli biofilms at single-cell resolution

Abstract

Biofilm formation on abiotic surfaces in the food and medical industry can cause severe contamination and infection, yet how biological and physical factors determine the cellular architecture of early biofilms and the bacterial behavior of the constituent cells remains largely unknown. In this study, we examined the specific role of type I fimbriae in nascent stages of biofilm formation and the response of microcolonies to environmental flow shear at the single-cell resolution. The results show that type I fimbriae are not required for reversible adhesion from plankton, but they are critical for the irreversible adhesion of Escherichia coli strain MG1655 cells that form biofilms on polyethylene terephthalate (PET) surfaces. Besides establishing firm cell surface contact, the irreversible adhesion seems necessary to initiate the proliferation of E. coli on the surface. After the application of shear stress, bacterial retention is dominated by the three-dimensional architecture of colonies, independent of the population size, and the multilayered structure could protect the embedded cells from being insulted by fluid shear, while the cell membrane permeability mainly depends on the biofilm population size and the duration of the shear stress.