Two microbes assisting Miscanthus floridulus in remediating multi-metal(loid)s contaminated soil

Abstract

Miscanthus has good tolerance to muti-metal(loid)s and has received increasing attention in remediated studies of metal(loid)s-contaminated soil. In this study, we explored the synergic effects of Miscanthus floridulus (Lab.) and two plant growth-promoting bacteria (PGPB), TS8 and MR2, affiliated to Enterobacteriaceae on remediation of muti-metal(loid)s contaminated soil. The results exhibited a decrease of metal(loid)s except for copper contents in the soil in bacterial inoculation groups, indicating that MR2 and TS8 could enhance the remediation of metal(loid)s. Moreover, increased fresh/dry weight and height indicated that inoculated bacteria could promote Miscanthus growth. Although the activities of antioxidant enzymes and the content of chlorophyll in the overground tissues showed no significant increase or even decrease, the activities of antioxidant enzymes in the underground tissues and soil, as well as the contents of soil nutrients (available K and P), were significantly (p < 0.05) increased to some certain. Bacterial inoculants could also decrease the soil pH. High-throughput sequencing analysis showed that the bacterial inoculant affected the rhizosphere bacterial community and reduced community diversity, but the relative abundance of some PGPB were found to increase. Phylogenetic molecular ecological networks indicated that bacterial inoculants reduced interactions between rhizosphere bacteria and thereby led to a simpler network structure but increased the proportion of positive-correlation links and enhanced the metabiosis and symbiosis of those bacteria. Spearman’s test showed that OTUs affiliated with Enterobacteriaceae and soil nutrients were critical for metal(loid) remediation and Miscanthus growth. The results of this study provide a basis for the synergic remediation of muti-metal(loid)s-contaminated soils by Miscanthus and PGPB and provide a reference for the subsequent regulation of Miscanthus remediation efficiency by the other PGPB or critical bacteria.