Resuscitating microbial seed banks alter plant-soil interactions

Background/Question/Methods: Plant productivity and fitness are influenced by complex interactions with soil microbiomes. Not only are soil microbiomes extremely diverse, they also exhibit tremendous metabolic heterogeneity. For example, ≥ 90% of bacteria and fungi in soil are dormant and make up a microbial seed bank. While seed banks are known to promote biodiversity through buffering ecological and evolutionary dynamics, dormancy may have complex effects in soils owing to the interaction among microbes, plants, and the environment. To test the effects of seed banks on plant-soil interactions, we conducted a six-week growth chamber experiment where we resuscitated microbial seed banks in soil containing Brassica rapa, a model plant organism with agriculturally important subspecies. We manipulated microbial seed banks through repeated application of recombinant resuscitation promoting factor (Rpf) to soil. Rpf is a bacterial protein that terminates dormancy by cleaving the β-(1,4) glycosidic bond in peptidoglycan, a major cell-wall component in virtually all bacteria.

Results/Conclusions: Total B. rapa plant biomass was 33% lower in the Rpf treatment compared to plants in the control treatment. This decrease in plant biomass was likely due to the effects of Rpf on the soil microbial communities. Specifically, Rpf significantly reduced soil respiration and bacterial abundance. In addition, Rpf had a marginally significant effect on soil microbial community structure as measured by 16S rRNA gene sequencing. Our results suggest that soil microbial seed banks can affect plant-soil interaction by determining the level of soil microbial activity, which has consequences for plant performance and soil feedbacks.