Vertical stratification of matrix production is essential for physical integrity and architecture of macrocolony biofilms of Escherichia coli

Bacterial macrocolony biofilms grow into intricate three‐dimensional structures that depend on self‐produced extracellular polymers conferring protection, cohesion and elasticity to the biofilm. In Escherichia coli, synthesis of this matrix – consisting of amyloid curli fibres and cellulose – requir...

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Bibliographic Details
Published in:Environmental microbiology 2015-12, Vol.17 (12), p.5073-5088
Main Authors: Serra, Diego O, Klauck, Gisela, Hengge, Regine
Format: Article
Language:English
Subjects:
agar
amyloid
Amyloid - metabolism
Bacterial Proteins - genetics
Bacteriology
biofilm
Biofilms - growth & development
cohesion
E coli
Escherichia coli
Escherichia coli - genetics
Escherichia coli - physiology
Escherichia coli Proteins - genetics
Extracellular Matrix - metabolism
polymers
Promoter Regions, Genetic - genetics
Sigma Factor - genetics
Stratigraphy
Trans-Activators - genetics
transcription factors
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Summary:Bacterial macrocolony biofilms grow into intricate three‐dimensional structures that depend on self‐produced extracellular polymers conferring protection, cohesion and elasticity to the biofilm. In Escherichia coli, synthesis of this matrix – consisting of amyloid curli fibres and cellulose – requires CsgD, a transcription factor regulated by the stationary phase sigma factor RpoS, and occurs in the nutrient‐deprived cells of the upper layer of macrocolonies. Is this asymmetric matrix distribution functionally important or is it just a fortuitous by‐product of an unavoidable nutrient gradient? In order to address this question, the RpoS‐dependent csgD promoter was replaced by a vegetative promoter. This re‐wiring of csgD led to CsgD and matrix production in both strata of macrocolonies, with the lower layer transforming into a rigid ‘base plate’ of growing yet curli‐connected cells. As a result, the two strata broke apart followed by desiccation and exfoliation of the top layer. By contrast, matrix‐free cells at the bottom of wild‐type macrocolonies maintain colony contact with the humid agar support by flexibly filling the space that opens up under buckling areas of the macrocolony. Precisely regulated stratification in matrix‐free and matrix‐producing cell layers is thus essential for the physical integrity and architecture of E. coli macrocolony biofilms.
ISSN:1462-2912
1462-2920
DOI:10.1111/1462-2920.12991