4.3.4 S cycling
Sulfur metabolism in microorganisms consists of redox reactions of organic and inorganic sulfur substrates that can play a major part in the biogeochemical cycle (Zerkle et al., 2010; Zopfi et al., 2008; Li et al., 2010; Treude et al., 2014; Gomes et al., 2017). As the same of denitrification, sulfate reduction is an anaerobic respiration that might be stronger in stagnant area. Nine of the fourteen detected sulfur metabolic genes had higher relative abundance in stagnant area than in runoff area (Fig.9c), suggesting enhanced microbial functional capacity for S cycling in stagnant area. These genes included dsrAB encoding dissimilatory sulfite reductase (p < 0.001), sir encoding sulfate reductase (p = 0.003), cysN encoding sulfate adenylyltransferase (p = 0.008), sat encoding sulfate adenylyltransferase (p = 0.00008), aprAB encoding adenylylsulfate reductase (p < 0.02) and PAPSS encoding 3’-phosphoadenosine 5’-phosphosulfate synthase (p = 0.03).