Abstract
BackgroundEncased 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.ResultsHere, 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.ConclusionsWith 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.
Highlights
Encased in a matrix of extracellular polymeric substances (EPS) composed of flagella, adhesins, amyloid fibers, and exopolysaccharides, 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
In Escherichia coli the extracellular matrix is formed by a variety of extracellular polymeric substances (EPS), adhesions: type-1 pili [11], amyloid fibers [12] and exopolysaccharides: cellulose [13], colanic acid [11,12], β-1,6-N-acetylD-glucosamine polymer (PGA) [14,15]
The genetic determinants and environmental cues that impact on pattern formation in E. coli old-macrocolony biolfilms are poorly understood
Summary
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. Biofilms are defined as matrix-enclosed communities of microorganisms tightly interacting with each other, attached as a whole to a living or non-living surface [9,10]. In Escherichia coli the extracellular matrix is formed by a variety of extracellular polymeric substances (EPS), adhesions: type-1 pili [11], amyloid fibers (curli) [12] and exopolysaccharides: cellulose [13], colanic acid [11,12], β-1,6-N-acetylD-glucosamine polymer (PGA) [14,15] (reviewed in reference [16]). It has been described that the type-1 pili and the outer membrane Ag43
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