Effects of curvature on growing films of microorganisms

TL;DR

This study investigates how the curvature of individual microorganisms influences the growth patterns and structural properties of microbial colonies on surfaces, revealing significant effects on colony morphology and internal organization.

Contribution

It introduces the consideration of cell curvature in models of microbial growth, showing qualitative changes in colony structure and emergent spatio-orientational coupling.

Findings

Curved cells form branched, stacked structures.

Colony domains are smaller with curved cells.

Emergent spatio-orientational coupling observed.

Abstract

To provide insight into the basic properties of emerging structures when bacteria or other microorganisms conquer surfaces, it is crucial to analyze their growth behavior during the formation of thin films. In this regard, many theoretical studies focus on the behavior of elongating straight objects. They repel each other through volume exclusion and divide into two halves when reaching a certain threshold length. However, in reality, hardly any object of a certain elongation is perfectly straight. Therefore, we here study the consequences of the curvature of individuals on the growth of colonies and thin active films. This individual curvature, so far hardly considered, turns out to qualitatively affect the overall growth behavior of the colony. Particularly, strings of stacked curved cells emerge that show branched structures, while the size of orientationally ordered domains in the colony is significantly decreased. Furthermore, we identify emergent spatio-orientational coupling that is not observed in colonies of straight cells. Our results are important for a fundamental understanding of the interaction and spreading of microorganisms on surfaces, with implications for medical applications and bioengineering.