Effects of curvature on growing films of microorganisms

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 curvature on the growth of colonies and thin active films. A given amount of curvature is prescribed to each growing individual. Particularly, we analyze how this individual curvature affects the size of orientationally ordered domains in the colony and find a significant decrease. Instead, strings of stacked curved cells emerge that show branched structures. Furthermore, we identify a significant 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.