Toxicity effects of aged refuse on Tagetes patula and rhizosphere microbes

Abstract Aged refuse, also named mineralized refuse, refers to garbage that has been buried in landfills for many years, has basically stabilized and can be mined and utilized. In this study, we examined the effects of different mass ratios of aged refuse on Tagetes patula and rhizosphere microbes. Compared to growth in ordinary soil, growth in aged refuse or mixed soil with aged refuse significantly increased chlorophyll content, activities of superoxide dismutase, catalase, and peroxidase, while it decreased malondialdehyde levels and protein carbonyl content in leaf tissue of Tagetes patula . Aged refuse was found to be enriched in a variety of rhizosphere microbes that contribute to pollutant degradation, although microbial diversity was found to be relatively low. Bacterial genera such as Ferruginibacter , Hymenobacter , unclassified _Gemmataceae , Longimicrobium , Tychonema CCAP 1459‐11B, Gemmatirosa , and Rubellimicrobium were depleted in soil: aged refuse groups compared with ordinary soil. Correspondingly, bacterial genera such as Emticicia , Caedibacter , Anaerosalibacter , Tumebacillus , Patulibacter , Oceanotoga , Dyadobacter , Chloroflexus , and Acidobacteria bacterium SCN 69–37, Polycyclovorans , were enriched in soil: aged refuse groups compared with ordinary soil. Furthermore, rhizosphere microbe functions changed markedly following the addition of aged refuse. These findings indicate that aged refuse may represent a source of environmental stress for plants and modifies the dominant bacterial composition of rhizosphere microbes. There were underlying close associations among pollutants, plant physiological stress responses, and rhizosphere microbial community composition. With respect to identifying potential approaches to recycling aged refuse, it will be necessary to focus on selecting optimal mass ratios of aged refuse and ordinary soil to control contaminant exposure.