Lead availability and soil microbial community composition in rice rhizosphere affected by thiosulfate addition

A pot experiment was carried out to study the sulfur (S) and lead (Pb) interaction and its impact on soil microbial community composition in rice rhizosphere soil under flooded conditions. Paddy soil was treated with a Pb gradient with and without thiosulfate addition and then planted with rice. The increasing addition of Pb resulted in plant yield reduction and high, phytotoxic concentrations of Pb in roots with relatively low concentration of Pb in shoots. Under the impact of thiosulfate, Pb uptake in plants and NH4OAc extractable Pb did not increase dramatically. PCR-DGGE experiment suggested that S action led to new bands. Specific clones (T3 and T6) found in S addition soils had high similarity to Thiobacillus, which indicated relatively high rates of potential S oxidation. S addition did not affect the availability Pb and the composition of soil microbial community. S addition is not a suitable amendatory tool of phytoremediation for Pb polluted soil.