Entrainment by biogenic bubbles enables long-range microbial dispersal in yield-stress environment

Microbial communities often inhabit confining three-dimensional environments, such as soils, sediments, foods, and biological gels and tissues. While some microbes can spread through their surroundings using motility, many are non-motile. Here, we show that even these non-motile microbes can escape their localized environments and disperse over long distances by riding bubbles generated through their metabolic activity. In our study, we focus on non-motile yeast growing in transparent three-dimensional granular hydrogel matrices. As the yeast ferment, they produce bubbles of carbon dioxide that grow, deform the surrounding matrix, and ultimately yield the matrix and rise, entraining yeast cells in their wake over large vertical distances. We show that the sequential entrainment of yeast cells by the train of rising bubbles ultimately culminates in the formation of a conduit within the matrix, encapsulating the colony and giving rise to a distinct columnar morphology. Our findings provide quantitative insights into the entrainment process driven by biogenic bubbles and demonstrate its connection to microbial dispersal. This research highlights the critical role of biogenesis in the proliferation and transport of living matter within complex environments, reflecting many biogeological processes observed in nature.