Bacteria Colonies Modify Their Shear and Compressive Mechanical Properties in Response to Different Growth Substrates.

Bacteria build multicellular communities termed biofilms, which are often encased in a self-secreted extracellular matrix that gives the community mechanical strength and protection against harsh chemicals. How bacteria assemble distinct multicellular structures in response to different environmental conditions remains incompletely understood. Here, we investigated the connection between bacteria colony mechanics and the colony growth substrate by measuring the oscillatory shear and compressive rheology of bacteria colonies grown on agar substrates. We found that bacteria colonies modify their own mechanical properties in response to shear and uniaxial compression in a manner that depends on the concentration of agar in their growth substrate. These findings highlight that mechanical interactions between bacteria and their microenvironments are an important element in bacteria colony development, which can aid in developing strategies to disrupt or reduce biofilm growth.

A Torsion-Based Rheometer for Measuring Viscoelastic Material Properties.

Rheology and the study of viscoelastic materials are an integral part of engineering and the study of biophysical systems. Tissue rheology is even used in the study of cancer and other diseases. However, the cost of a rheometer is feasible only for colleges, universities, and research laboratories. Even if a rheometer can be purchased, it is bulky and delicately calibrated, limiting its usefulness to the laboratory itself. The design presented here is less than a tenth of the cost of a professional rheometer. The design is also portable, making it the ideal solution to introduce viscoelasticity to high school students as well as for use in the field for obtaining rheological data.