Bacterial community response to cadmium contamination of agricultural paddy soil

Abstract

Heavy metal pollution of paddy fields is of increasing concern due to the huge losses in rice yield that occur every year. Therefore, it is important to understand the microecological and physicochemical changes to paddy soil under varying cadmium (Cd) pollution levels. Here, we explore the bacterial community response to cadmium contamination of agricultural paddy soil. Our results reveal that high cadmium level sites displayed lower diversity indices than low cadmium level groups. In addition, total and available cadmium exhibited significant negative correlations with diversity indices. The dominant phyla that were observed in the paddy soil samples included Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Gemmatimonadetes, Verrucomicrobia, Thaumarchaeota, Firmicutes, and Nitrospirae. The results suggest that Actinobacteria are tolerant to cadmium, whereas Proteobacteria, Verrucomicrobia, and Nitrospirae are sensitive. According to the results of pCoA, bacterial communities were differentiated across cadmium pollution levels, suggesting that the active members of the microbial communities under cadmium stress were different from those in the control soils. In addition, Mantel tests showed that the overall bacterial community structure significantly correlated with total pH, available phosphorus (AP), organic matter (OM), total cadmium (TCd), and available cadmium (ACd).