Abiotic stress reorganizes rhizosphere and endosphere network structure of Sorghum bicolor

Sorghum bicolor is a promising bioenergy feedstock with high biomass production and unusual tolerance for stresses such as water and nutrient limitation. While the membership of the sorghum microbiome in response to stress has been explored, relatively little is known about how microbe-microbe networks change under water- or nutrient-limited conditions. This is important because network changes can indicate impacts on the functionality and stability of microbial communities. We performed network-based analysis on the core bacterial and archaeal community of an agronomically promising high biomass bioenergy genotype, Grassl, grown under nitrogen and water stress. Stress caused relatively minor changes in bacterial abundances within soil, rhizosphere, and endosphere communities, but led to significant changes in bacterial network structure and modularity. We found a complete reorganization of network roles in all plant compartments as well as an increase in the modularity and proportion of positive associations which potentially could represent coexistence and cooperation in the sorghum bacterial/archaeal community under stress. While stressors are often believed to be destabilizing, we found stressed networks were as or more stable than non-stressed networks likely due to their redundancy and compartmentalization. Together, these findings support the idea that both sorghum and its bacterial/archaeal community can be resilient to future environmental stressors.