Morphogenesis and cell ordering in confined bacterial biofilms

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Biofilms are bacterial communities encased in an extracellular matrix.
• Studying biofilm growth in 3D confined environments is challenging.
• Understanding how biofilms interact with and deform their surroundings is crucial.

Purpose of the Study:

• To investigate the biophysical mechanisms of biofilm development in 3D confined environments.
• To elucidate the role of environmental stiffness in biofilm morphogenesis.
• To compare the growth dynamics of embedded biofilms with those on flat surfaces.

Main Methods:

• Single-cell imaging
• Mutagenesis studies
• Rheological measurements
• Theoretical modeling of growing inclusions in elastic media.

Main Results:

• Vibrio cholerae biofilms in hydrogels grow by four orders of magnitude.
• Embedded biofilm morphodynamics and cell ordering differ significantly from surface biofilms.
• Environmental stiffness determines biofilm morphology (spherical vs. oblate ellipsoidal) and internal cell ordering.
• Cell ordering in stiff gels resembles nematic liquid crystal structures and arises from matrix-mediated stress transmission.

Conclusions:

• Biofilm morphology and internal architecture are governed by the stiffness contrast between the biofilm and its environment.
• Cells in confined biofilms self-organize in response to mechanical constraints.
• The developed imaging and theoretical approaches are applicable to other biofilm systems, including those in host tissues.