Understanding how organisms move is key to explaining why certain species live where they do. For example, dispersal limitation helps explain why penguins don’t live in the North Pole. In ecology, dispersal of plants and animals is often characterized by how far an individual travels from a starting point and the rate they move into new areas. However, for microorganisms, directly tracking individual cells in the field remains a technical challenge.
In this study, the researchers developed a new method to address the question: how many microbes arrive in a new location, and how far did they travel? This question lies at the heart of a long-standing debate in microbial ecology—whether microbial dispersal is limited or if “everything is everywhere.” The study focuses on soil microbes, which drive essential ecosystem processes such as nutrient cycling. By understanding the limits of soil microbial dispersal, the researchers aim to gain insight into the processes that determine which microbes are present and, consequently, influence ecosystem functioning.
It was discovered that microbial movement into soil is more limited than previously thought. The species that disperse into the soil at one location differ from those dispersing just one meter away. Because of their small size, it was commonly assumed that bacterial and fungal cells are easily transported over long distances through dispersal routes such as wind. However, using simple spatial analyses comparing potential dispersal sources and the microbial species entering the soil surface, the researchers found that the composition of microbes moving into topsoil varies at very small spatial scales. The rate at which bacteria were dispersing into soil (1060 ± 90 cells/cm²/day) was also measured, contributing to this small yet growing body of knowledge.
This study demonstrates that microbial dispersal can be studied in a similar way to plant and animal dispersal, using microbial “traps.” The results quantify the importance of the dispersal process on the assembly of soil microbial communities. Estimates of dispersal rates and the spatial scales of microbial movement serve as parameters for building predictive models of microbial dynamics in soils and across ecosystems. In addition, this research has practical implications for explaining why microbial communities differ between ecosystems and for ecological restoration efforts that assume that microbes will “move in” naturally.
Read the full journal article titled Microbial dispersal into surface soil is limited on a meter scale in The ISME Journal. This article has been selected as Editor’s Choice for the month of September 2025.
Authors
- Kendra Walters, University of California Irvine, USA
- Kristin Barbour, University of California Irvine, USA
- John Powers, University of California Irvine, USA
- Jennifer Martiny, University of California Irvine, USA