Biophysical constraints on vertical biofilm growth*

The development of surface-attached bacterial biofilms is one of the most common modes of bacterial growth in natural environments and experimental settings. While extensive research has sought to understand the radial growth of biofilms, fundamental questions remain about the vertical growth dynamics of biofilms. In a recent study [1], it was observed that colony height saturates on long time scales for a wide range of microorganisms. It was also observed that the vertical growth rate decreased as a slow linear function of biofilm height; surprisingly, nutrient depletion in the environment is not the cause of this slowing, and eventual cessation, of vertical growth. We have thus been performing experiments to determine why vertical growth slows. Using interferometry and confocal imaging techniques, we investigate how different factors such as cell death and viscous relaxation affect biofilm heights. Inspired by recent work [2], we have been investigating the role of starvation within the biofilm, i.e., the behavior of cells too far from the agar surface for nutrients to reach them. Our ongoing investigations aim to unravel the interplay of different factors influencing biofilm growth. By shedding light on the mechanisms governing the vertical expansion and stability of these bacterial colonies, we hope to contribute to a deeper understanding of microbial communities in various environmental contexts and pave the way for potential applications in fields such as biotechnology and medicine.

[1] P. Bravo, et al., PNAS (2023)

[2] H.Kannan, P.Sun, et al., bioRxiv, doi.org/10.1101/2023.08.27.554977 (2023)