Effect of pathogen Globisporangium ultimum on plant growth and colonizing bacterial communities

Plants recruit plant-associated microbes from soil to enhance their growth and mitigate the adverse effects of pathogen invasion on plant health. How pathogens impact the interactions of the plant-associated microbes and plant growth is poorly understood. We established S-microsystems (sterile soil inoculated with 101 bacteria isolated from humus soil with Artemisia annua, Oryza sativa or Houttuynia cordata), and N-microsystems (natural soil with these plants) to evaluate the effects of the fungus Globisporangium ultimum on plant growth and their colonizing bacterial communities (CBCs). S-microsystems and N-microsystems were inoculated with and without G. ultimum, respectively. Their seedling growth and CBCs were investigated. Plant height and root numbers in A. annua, O. sativa and H. cordata S-microsystems with G. ultimum were 34.5 % and 52.8 %, 23.1 % and 31.3 %, 102.1 % and 45.0 % higher than those without G. ultimum, respectively. The CBCs were diverse among S-microsystems of A. annua, O. sativa and H. cordata, and the CBC abundances in the three S-microsystems without G. ultimum were higher than those with G. ultimum. The relative abundances of bacterial genera Rhizobium, Pseudomonas, Brevundimonas and Cupriavidus were significantly positively related to plant growth. We determined that the CBCs in A. annua, O. sativa and H. cordata were selective and related to the plant species, and can mitigate disadvantageous influences of G. ultimum on seedling growth. The plants and their CBCs' abundance and composition were differentially affected by G. ultimum. Our results provide evidence that CBCs promote plant growth due to dynamic changes in the composition and abundance of CBC members, which were affected by plant species and biotic factors.