Performance and microbial mechanism in sulfide-driven autotrophic denitrification by different inoculation sources in face of various sulfide and sulfate stress

[Display omitted] •Original IS had lower denitrification and S cycle genes in IS than those of AS.•Biofilm inoculated by IS enriched more functional genes than by AS in SAD systems.•Biofilm domesticated by IS had more S cycle genes at high stress of S2- and SO42-•Microbes for S cycle more sensitive to the toxicity of S2- than denitrifiers. To develop a reliable sulfide (S2-) autotrophic denitrification (SAD) process under S2- and SO42- salinity stresses, the biofilm performance and microbial mechanisms were comparatively studied using different inocula of activated sludge (AS) and intertidal sediment (IS). Biofilm IS enriched more denitrification genes (0.34 %) and S2- oxidation genes (0.29 %) than those with AS. Higher denitrification performance was obtained under S2- (100 mg/L) and SO42- (5–15 g/L Na2SO4) stresses, but no significantly differences were observed under levels of 0–200 mg/L S2- and 30 g/L Na2SO4. Notably, biofilm samples in SAD systems with IS still had more S2- oxidation genes at high S2- levels of 100–200 mg/L and Na2SO4 level of 30 g/L. The key functional genus Thiobacillus accumulated well at 30 g/L Na2SO4, but was strongly inhibited at 200 mg/L S2-. The findings were advantage to SAD application under sulfide and salinity stresses.