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Abstract Background Cadmium (Cd) contamination in soil poses a serious safety risk for the development of medicine and food with ginseng as the raw material. Microorganisms are key players in the functioning and service of soil ecosystems, but the effects of Cd-contaminated ginseng growth on these microorganisms is still poorly understood. To study this hypothesis, we evaluated the effects of microorganisms and Cd (0, 0.25, 0.5, 1.0, 2.0, 5.0, and 10.0 mg kg-1 of Cd) exposure on the soil microbial community using Illumina HiSeq high-throughput sequencing. Results Our results indicated that Cd-contaminated soil affected the soil microbial diversity and composition, and bacterial diversity was affected more than fungal diversity in Cd-contaminated soil, especially according to Shannon indices. The abundance of the soil microbial community decreased and the composition changed according to the relative abundances at the phylum level, including those of Saccharibacteria and Gemmatimonadetes in bacteria and Mortierellomycota in fungi. The LEfSe algorithm was used to identify active biomarkers, and 45 differentially abundant bacterial taxonomic clades and 16 differentially abundant fungal taxonomic clades were identified with LDA scores higher than 4.0. Finally, a heatmap of Spearman's rank correlation coefficients and canonical discriminant analysis (CDA) indicated that some key biomarkers, Arenimonas, Xanthomonadales, Nitrosomonadaceae, Methylophilales, Caulobacterales, Aeromicrobium, Chitinophagaceae, Acidimicrobiales, Nocardioidaceae, Propionibacteriales, Frankiales, and Gemmatimonadaceae, were positively correlated with the total and available Cd (p

Abstract Background This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax. We explored the differences in soil physical and chemical factors and microbial community structure following Si application as well as the key factors that affected the occurrence of ginseng black spot in soil. Potted Panax ginseng plants were used to assess the effect of Si treatment on ginseng black spot. Soil physical and chemical properties were comprehensively analyzed. Bacterial communities were analyzed using Illumina HiSeq sequencing targeting the 16S rRNA gene. Results After inoculation with A. panax, the morbidity (and morbidity index) of ginseng with and without Si was 52% (46) and 83% (77), respectively. Soil physical and chemical analysis showed that under the ginseng black spot inoculation, bacterial communities were mainly affected by pH and available potassium, followed by ammonium nitrogen and available Si. NMDS and PLS-DA analyses and the heat maps of relative abundance revealed that Si application elevated the resistance of ginseng black spot as regulated by the abundance and diversity of bacterial flora in rhizosphere soils. Heatmap analysis at the genus level revealed that A. panax + Si inoculations significantly increased the soil community abundance of Sandaracinus, Polycyclovorans, Hirschia, Haliangium, Nitrospira, Saccharothrix, Aeromicrobium, Luteimonas, and Rubellimicrobium and led to a bacterial community structure with relative abundances that were significantly similar to that of untreated soil. Conclusions Short-term Si application also significantly regulated the structural impact on soil microorganisms caused by ginseng black spot. Our findings indicated that Si applications may possibly be used in the prevention and treatment of ginseng black spot.