Paper Number
AD15
Session
Rheology of Active Matter and Directed Systems
Title
Roughening instability of growing 3D bacterial colonies
Presentation Date and Time
October 13, 2022 (Thursday) 9:45
Track / Room
Track 4 / Gold Coast
Authors
- Martinez-Calvo, Alejandro (Princeton University)
- Bhattacharjee, Tapomoy (Princeton University)
- Bay, R. Konane (Princeton University)
- Luu, Hao Nghi (Princeton University)
- Hancock, Anna M. (Princeton University)
- Wingreen, Ned S. (Princeton University)
- Datta, Sujit S. (Princeton University)
Author and Affiliation Lines
Alejandro Martinez-Calvo, Tapomoy Bhattacharjee, R. Konane Bay, Hao Nghi Luu, Anna M. Hancock, Ned S. Wingreen and Sujit S. Datta
Princeton University, Princeton, NJ
Speaker / Presenter
Datta, Sujit S.
Keywords
experimental methods; theoretical methods; computational methods; active matter; bio-fluids; biomaterials; flow-induced instabilities
Text of Abstract
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 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. Moreover, our analysis draws tantalizing connections between the growth of bacterial colonies and other forms of surface roughening that have been observed in non-living systems, such as growing snowflakes, colloidal aggregates, and mineral deposits in batteries---motivating further studies of the similarities and differences between growing living and non-living systems.