Fig. 3: The main microbial taxa responsible for incorporating ¹³C from the spiked ¹³C-labeled methylmercury (¹³CH₃Hg⁺) in soils.

A, B Bacterial community composition represented by the most abundant families (top 20) in the fraction of the highest 16S rRNA gene copies from ¹³CH₃Hg⁺ treatment and the corresponding fraction in ¹²CH₃Hg⁺ treatment at day 28 in the SIP experiments of the paddy soil from high Hg contaminated site (High-P) and upland soil from low Hg contaminated site (Low-U), respectively. C Biomarkers of key genera in the fraction of the highest 16S rRNA gene copies from ¹³CH₃Hg⁺ treatment and the corresponding fraction in ¹²CH₃Hg⁺ treatment of High-P soil. D Relative abundances of enriched genera across CsCl gradient fractions at ¹²CH₃Hg⁺ and ¹³CH₃Hg⁺ treatments of High-P soil. E Biomarkers of key genera in the fraction of the highest 16S rRNA gene copies from ¹³CH₃Hg⁺ treatment and the corresponding fraction in ¹²CH₃Hg⁺ treatment of Low-U soil. F Relative abundances of enriched genera across CsCl gradient fractions at ¹²CH₃Hg⁺ and ¹³CH₃Hg⁺ treatments of Low-U soil. Vertical bars in (D, F) represent standard deviations of the relative abundance (three biological replicates, n = 3) in the ¹²CH₃Hg⁺ (control) and ¹³CH₃Hg⁺ treatments, and horizontal error bars in (D, F) represent the standard deviations of the buoyant density of the same order fractions (three biological replicates, n = 3) in the ¹²CH₃Hg⁺ (control) and ¹³CH₃Hg⁺ treatments. The data in (D, F) are presented as mean values ± standard deviation. Source data are provided as a Source Data file.