The soil is not just a single environment. To human eyes it may look like a brown layer of plant mush that fits into the rocks, but for a living environment it is highly complex. Not only must the bacteria that live within it share their space with small animals, protozoa, and fungi, but they also have to work around giant complexes of tree roots throughout the soil. These tree roots aren’t just static objects to be built around though, they take an active part in both influencing and shaping the microbial communities around them.
As an (ex)-biochemist I’m used to the idea of studying plant-microbe interactions by taking one plant and one microbe and seeing what chemicals they produce, so I was fascinated by recent research from the University of North Carolina that looked at entire microbial ecosystems. The researchers went outside, collected two types of soil from different locations and grew samples of the plant Arabidopsis in each one. They then collected soil that had grown around the roots and looked at the bacterial species within that soil, as well as the bacterial species growing within the root itself.
Collaboration with a NextGen sequencing team (the Department of Energy’s Joint Genome Institute) allowed them to identify the different bacterial species present. They found that a subset of all the bacteria in the soil were found clustered around the roots, while an even smaller subset were allowed inside. Looking for similarities between the bacteria from each plant revealed a core microbiome, a set of specific bacterial species that the plant was attracting from the soil towards itself.