Toxicity effects of improved aged refuse on Tagetes patula and
rhizosphere microbes
Abstract
In this study, we examined the effects of different mass ratios of aged
refuse on Tagetes patula and rhizosphere microbes. The results showed
that chlorophyll content and activities of superoxide dismutase,
catalase, and peroxidase in leaf tissue increased significantly in
plants cultivated in soil:aged refuse mixtures compared with ordinary
soil, whereas levels of malondialdehyde and protein carbonyl decreased
significantly in soil:aged refuse mixtures. Microbial community analysis
revealed that aged refuse is rich 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 tended to be enriched to a greater extent in ordinary
soil compared with soil:aged refuse mixtures. Correspondingly, bacterial
genera such as Emticicia, Caedibacter, Anaerosalibacter, Tumebacillus,
Patulibacter, Oceanotoga, Dyadobacter, Chloroflexus, and Acidobacteria
bacterium SCN 69-37, Polycyclovorans, tended to be enriched in mixtures
with a higher proportion of aged refuse. Functional prediction analysis
revealed that 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. The
combination of organic or inorganic pollutants, plant physiological
stress responses, and rhizosphere microbial community composition may
have potential cooperative or dynamic equilibrium relationships. 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.