Surface indentation and fluid intake generated by the polymer matrix of Bacillus subtilisbiofilms

Bacterial biofilms are highly structured, surface associated bacteria colonies held together by a cell-generated polymer network known as EPS (extracellular polymeric substance). This polymer network assists in adhesion to surfaces and generates spreading forces as colonies grow over time. In the la...

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Bibliographic Details
Published in:Soft matter 2015-04, Vol.11 (18), p.3612-3617
Main Authors: Zhang, W, Dai, W, Tsai, Shi-Ming, Zehnder, S M, Sarntinoranont, M, Angelini, TE
Format: Article
Language:English
Subjects:
Bacillus
Bacteria
Biofilms
Colonies
EPS
Fluid dynamics
Fluid flow
Fluids
Networks
Stresses
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Summary:Bacterial biofilms are highly structured, surface associated bacteria colonies held together by a cell-generated polymer network known as EPS (extracellular polymeric substance). This polymer network assists in adhesion to surfaces and generates spreading forces as colonies grow over time. In the laboratory and in nature, biofilms often grow at the interface between air and an elastic, semi-permeable nutrient source. As this type of biofilm increases in volume, an accommodating compression of its substrate may arise, potentially driven by the osmotic pressure exerted by the EPS against the substrate surface. Here we study Bacillus subtilisbiofilm force generation by measuring the magnitude and rate of deformation imposed by colonies against the agar-nutrient slabs on which they grow. We find that the elastic stress stored in deformed agar is orders of magnitude larger than the drag stress associated with pulling fluid through the agar matrix. The stress exerted by the biofilm is nearly the same as the osmotic pressure generated by the EPS, and mutant colonies incapable of producing EPS exert much lower levels of stress. The fluid flow rate into B. subtilisbiofilms suggest that EPS generated pressure provides some metabolic benefit as colonies expand in volume. These results reveal that long-term biofouling and colony expansion may be tied to the hydraulic permeability and elasticity of the surfaces that biofilms colonize.
ISSN:1744-683X
1744-6848
DOI:10.1039/c5sm00148j