Resuscitating the microbial seed bank alters plant-soil interactions

Soil microorganisms strongly influence plants through performing ecological services that promote biomass production and fitness. Despite the importance of soil microorganisms, the vast majority (≤ 90%) of bacteria and fungi in soil are dormant and do not participate in plant-microbe interactions. While dormancy in microbial communities promote biodiversity through buffering ecological and evolutionary dynamics, microbial dormancy may have effects on plant performance through altering the activity, abundance, and diversity of soil microbial community. To test the effects of microbial dormancy on plant-soil interactions, we conducted a six-week growth chamber experiment using Brassica rapa and we resuscitated the soil microbial seed bank through weekly application of a bacterial protein, called resuscitation promoting factor (Rpf), that terminates bacterial dormancy by degrading peptidoglycan. Total plant biomass was ~33% lower under Rpf treatment compared to plants growing with an unmanipulated microbial seed bank. In addition, Rpf treatment reduced overall soil respiration, decreased bacterial abundance, increased fungal abundance, and altered soil bacterial community structure. Although we did not observe a negative effect of resuscitating the microbial seed bank on soil bacterial community diversity, our results still demonstrate the critical role of dormancy in maintaining beneficial plant-microbe interaction through regulating soil microbial community activity and composition dynamics.