Evaluation of Microbial Community Activity, Abundance and Structure in a Semiarid Soil Under Cadmium Pollution at Laboratory Level

Cadmium (Cd) pollution can alter soil flora and fauna, as well as the microbial community associated with the main biogeochemical cycles of a soil. The present study was conducted to investigate the effect of two different concentrations of Cd pollutant, 6.5 mg kg(-1) (low level) and 12.5 mg kg(-1) (high level) on microbial community activity, abundance, and structure in a semiarid soil after a 60-day incubation period at laboratory level. Available Cd, water soluble carbon (WSC), microbial biomass carbon (C-mic), adenosine triphosphate (ATP) content, and real-time polymerase chain reaction were used to measure the influence of Cd on the abundance and activity of the microbial community. Bacteria and fungi community structure and diversity based on denaturing gradient gel electrophoresis (DGGE) analysis were also analyzed. The percentage of Cd extracted by diethylenetriamine pentaacetic acid increased with the higher total concentration of Cd added to the soil, being 16.9% at low level and 77.9% at the high level. WSC, C-mic, and ATP content decreased significantly as soil Cd concentration increased (WSC 29% and 34%, C-mic 27% and 35%, and ATP 32% and 47%, at low and high levels, respectively). While fungal diversity already decreased with low levels of Cd concentration, and was even more negatively affected by the higher pollution levels, bacterial (acidobacteria, alpha-proteobacteria, and beta proteobacteria) diversity only showed a decline with the higher Cd concentration. The fungi-to-bacteria ratio showed by the different treatments could imply that fungi abundance is less influenced by increased Cd pollution, although fungi diversity as revealed by DGGE analysis diminished as soil Cd concentration increased.