Unexpectedly dense colonization of soil pore space by microbes

Abstract Pore surfaces in soil are considered to be sparsely colonised, dispersed only with isolated cells or colonies of bacteria and archaea. Here, we question this ‘empty space’-concept by combining microstructure analysis with molecular biology and provide a data-driven update on habitable surface areas (HSA) in soil. Our unique approach allowed us to provide 1) evidence that microbial densities in soil have been underestimated for decades and 2) two-dimensional simulations of their potential distribution within the soil pore space. Our results demonstrate the need for a new perspective on how densely soil is colonised, with implications for how we think of basic ecological processes such as microbial motility or predation, and how microbial processes, including organic matter dynamics, are ultimately modelled.