Mechanisms of response of rare and abundant species in rhizosphere soils of Coriaria nepalensis Wall. to heavy metal remediation of lead-zinc tailings

The increasing environmental pollution caused by metal tailings has become a global environmental problem. Rhizosphere microorganisms play a key role in phytoremediation of heavy metal pollution. However, the role of abundant and rare species in the phytoremediation of tailings remains to be investigated further. The rhizosphere and non-rhizosphere soils of Coriaria nepalensis Wall. in tailings and non-tailings areas were collected separately and Geochemical properties, soil enzyme activity and heavy metal content were measured. Differences between abundant and rare species were also exposed through macrogenomes and macro-metabolomes. The results show that due to the strong enrichment of heavy metals such as lead and zinc, heavy metals in the rhizosphere soil inhibited soil nutrient cycling. They exacerbated the resistance mechanism of rhizosphere microorganisms to heavy metals. The two ecological strategies of abundant and rare species to cope with heavy metal stress were elaborated through the joint analysis of metagenome and metabonomics. The abundance of species was significantly higher than that of rare species in most gene expressions, and they relied on gene expression to improve their tolerance and maintain their basal survival and reproduction. Rare species, on the other hand, play an important role in the expression of key genes (e.g., cdhD, cdhE, CHS1, yesX, pelC, 6GAL, PIGL, GES3_5, CES1, iaaM, czcA, NIT-6, sor) as well as in the secretion of metabolites, responding to the dynamic stresses through inducible metabolites. We found that rare species play a more critical role in the phytoremediation of tailings.