Biology subjects

Bay, R. K.

Publications and source records attributed to Bay, R. K..

3 recordsLinked to original sources

bioRxiv2025

Engineering Biohybrid Mycelium Fibers through Hierarchical Structuring and Biomineralization

Driven by the persistence of microplastics and an overdependence on non-renewable sources, mycelium materials have emerged as alternatives to traditional materials, owing to their sustainable production and versatility. Engineered living materials, composite material systems incorporating biological components to enable function, possess desirable regenerative properties but have yet to be fully applied due to their lack of strength versus synthetic or natural materials. We leverage two strategies used by nature to generate mechanical strength: structural hierarchy and biomineralization. We extrude a bioink composed of alginate and a modified strain of the fungus Aspergillus niger capable of silica mineralization, and modulate the morphology by the growth and processing conditions. Mineralization results in significantly stronger and stiffer dried fibers. We demonstrate their potential as textile materials through twisting and braiding to significantly increase the fracture strain. Our results show that mycelium morphology and mechanics can be tuned through mineralization, growth conditions, and processing.

bioengineering↗

bioRxiv2025

Strengthening Biofilms with Selective Metal Ions

Biofilms are structured microbial communities consisting of bacteria embedded in a self-produced extracellular polymeric substance (EPS) that enables survival in diverse environments. The EPS integrates materials from the surrounding environment, such as metal ions, to provide additional mechanical protection to the embedded bacteria from environmental stressors. While previous studies demonstrated metal ions impact the erosion behavior of biofilms, key quantitative properties, such as yield stress, remain largely undocumented due to difficulties in handling these viscoelastic and soft biomaterials. In this work, we introduce a technique to characterize the impact of metal ions on the uniaxial stress-strain response of bacterial biofilms. Through applying this method to Bacillus subtilis pellicles, we demonstrate that the absorption of selective metal ions into the EPS significantly increases both the elastic modulus and yield stress, while decreasing failure strain. Notably, this effect can be reversed through the introduction of a strong chelating agent--while variations in pH alone have a negligible impact on measured mechanical properties. We compare our results to previous biofilm erosion studies and provide insights into how metal ions interactions can alter the mechanical behavior of biofilms, which will aid in future biofilm mitigation strategies for biofouling or healthcare applications.

microbiology↗

bioRxiv2022

Roughening instability of growing 3D bacterial colonies

How do growing bacterial colonies get their shapes? While colony morphogenesis is well-studied in 2D, many bacteria grow as large colonies in 3D environments, such as gels and tissues in the body, or soils, sediments, and subsurface porous media. Here, we describe a morphological instability exhibited by large colonies of bacteria growing in 3D. Using experiments in transparent 3D granular hydrogel matrices, we show that dense colonies of four different species of bacteria--Escherichia coli, Vibrio cholerae, Pseudomonas aeruginosa, and Komagataeibacter sucrofermentans--generically roughen as they consume nutrients and grow beyond a critical size, eventually adopting a characteristic branched, broccoli-like, self-affine morphology independent of variations in the cell type and environmental conditions. This behavior reflects a key difference between 2D and 3D colonies: while a 2D colony may access the nutrients needed for growth from the third dimension, a 3D colony inevitably becomes nutrient-limited in its interior, driving a transition to rough growth at its surface. We elucidate the onset of roughening using linear stability analysis and numerical simulations of a continuum model that treats the colony as an active fluid whose dynamics are driven by nutrient-dependent cellular growth. We find that when all dimensions of the growing colony substantially exceed the nutrient penetration length, nutrient-limited growth drives a 3D morphological instability that recapitulates essential features of the experimental observations. Our work thus provides a framework to predict and control the organization of growing colonies--as well as other forms of growing active matter, such as tumors and engineered living materials--in 3D environments.

biophysics↗