Motile bacteria act as pump to move water through soil matrices

Rhizosphere microbiomes are known to enhance plants’ resistance to drought, and this effect has been mainly accredited to fungi and their capacity to transport and uptake water. Here, we studied how mechanical energy from motile bacteria can also contribute to water transport in soil, a mechanism we termed microbial pumps. We ran a series of microcosm and apparent surface tension experiments using different motility mutant strains of Bacillus subtilis, and characterised water transport in the pore space. Results confirmed that flagellar-based motility enhances the movements of water in soil reducing the apparent surface tension of the fluid and promotes the rewetting of dry hydrophobic regions of the soil. The effect was confirmed to be biomechanical because it was dependent on cell density and swimming speed. Collectively, these results highlight the potential of motile microorganisms to enhance water availability for crops.