Effects of endophytes inoculation on rhizosphere and endosphere microecology of Indian mustard (Brassica juncea) grown in vanadium-contaminated soil and its enhancement on phytoremediation

We investigated the effects of endophytes inoculation on ecological factors such as root morphology, rhizosphere soil properties, heavy metal speciation, and rhizosphere and endophytic bacterial communities and their role on phytoremediation. Indian mustards were grown for two months in V-contaminated soil with three treatments (control, inoculation with Serratia PRE01 or Arthrobacter PRE05). Inoculation with PRE01 and PRE05 increased organic matter content by 6.94% and 4.6% respectively and significantly increased bioavailability of heavy metals in rhizosphere soils. Despite the endophyte inocula failed to flourish as stable endophytes, they significantly affected the specific composition and diversity of endophytic bacterial communities in roots, with no significant effect on rhizosphere bacterial communities. The test strains could greatly increase plant growth promotion-related biomarkers in the endosphere, especially those associated with Pseudomonas and Microbacterium genera. PICRUSt analysis predicted high relative abundances of functional genes related to environmental information processing especially in the endophytic microbiota. More biomass production (12.0%-17.4%) and total metals uptake (24.2%-32.0%) were acquired in inoculated treatments. We conclude that endophyte PRE01 or PRE05 inoculation could effectively enhance phytoremediation of V-contaminated soil by improving the rhizosphere and endosphere microecology without causing any ecological damage.