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Open Access Research article

Crowning: a novel Escherichia coli colonizing behaviour generating a self-organized corona

José María Gómez-Gómez12* and Ricardo Amils13

Author Affiliations

1 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

2 OAS-BioAstronomy Group, Observatorio Astronómico de Segurilla (OAS), 45621, Camino de Valparaiso S/N, Segurilla Toledo, Spain

3 Centro de Astrobiología (CSIC-INTA), (Associated with NASA Astrobiology Institute), Ctra Ajalvir km 4, Torrejón de Ardoz, Madrid 28850, Spain

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BMC Research Notes 2014, 7:108  doi:10.1186/1756-0500-7-108

Published: 25 February 2014

Abstract

Background

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.

Results

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.

Conclusions

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.

Keywords:
Biofilms; Escherichia coli’s corona; Crowning behaviour; Macrocolony biofilm; CsgD-independent behaviour; Glucose repression; CRP-independent behaviour