RESUMEN
Introduction: The lack of systematic investigations of arbuscular mycorrhizal fungi (AMF) community composition is an obstacle to AMF biotechnological applications in antimony (Sb)- and arsenic (As)-polluted soil. Methods: Morphological and molecular identification were applied to study the AMF community composition in Sb- and As-contaminated areas, and the main influencing factors of AMF community composition in Sb- and As-contaminated areas were explored. Results: (1) A total of 513,546 sequences were obtained, and the majority belonged to Glomeraceae [88.27%, 193 operational taxonomic units (OTUs)], followed by Diversisporaceae, Paraglomeraceae, Acaulosporaceae, Gigasporaceae, and Archaeosporaceae; (2) the affinity between AMF and plants was mainly related to plant species (F = 3.488, p = 0.022 < 0.050), which was not significantly correlated with the total Sb (TSb) and total As (TAs) in soil; (3) the AMF spore density was mainly related to the available nitrogen, available potassium, and total organic carbon; (4) The effect of soil nutrients on AMF community composition (total explanation: 15.36%) was greater than that of soil Sb and As content (total explanation: 5.80%); (5) the effect of TAs on AMF community composition (λ = -0.96) was more drastic than that of TSb (λ = -0.21), and the effect of As on AMF community composition was exacerbated by the interaction between As and phosphorus in the soil; and (6) Diversisporaceae was positively correlated with the TSb and TAs. Discussion: The potential impact of As on the effective application of mycorrhizal technology should be further considered when applied to the ecological restoration of Sb- and As-contaminated areas.
RESUMEN
The microorganisms that co-exist between soil and rice systems in heavy metal-contaminated soil environments play important roles in the heavy metal pollution states of rice, as well as in the growth of the rice itself. In this study, in order to further examine the effects of soil microorganisms on the mercury (Hg) uptake of rice plants and determine potential soil phytoremediation agents, an enriched 199Hg isotope was spiked in a series of pot experiments to trace the absorption and migration of Hg and rice growth in the presence of arbuscular mycorrhizal fungi (AMF). It was observed that the AMF inoculations significantly reduced the Hg concentration in the rice. The Hg concentration in rice in the AMF inoculation group was between 52.82% and 96.42% lower than that in the AMF non-inoculation group. It was also interesting to note that the presence of AMF tended to cause Hg (especially methyl-Hg (Me199Hg)) to migrate and accumulate in the non-edible parts of the rice, such as the stems and leaves. Under the experimental conditions selected in this study, the proportion of Me199Hg in rice grains decreased from 9.91% to 27.88%. For example, when the exogenous Hg concentration was 0.1 mg/kg, the accumulated methyl-Hg content in the grains of the rice in the AMF inoculation group accounted for only 20.19% of the Me199Hg content in the rice plants, which was significantly lower than that observed in the AMF non-inoculated group (48.07%). AMF also inhibited the absorption of Hg by rice plants, and the decrease in the Hg concentration levels in rice resulted in significant improvements in growth indices, including biomass and micro-indexes, such as antioxidant enzyme activities. The improvements occurred mainly because the AMF formed symbiotic structures with the roots of rice plants, which fixed Hg in the soil. AMF also reduce the bioavailability of Hg by secreting a series of substances and changing the physicochemical properties of the rhizosphere soil. These findings suggest the possibility of using typical co-existing microorganisms for the remediation of soil heavy metal contamination and provide valuable insights into reducing human Hg exposure through rice consumption.