Metabolic Profile of the Soil Microbial Community Exposed to Arsenite and Arsenate: a 1-Year Experiment

Arsenic (As) is a soil contaminant with important interactions with the soil microbial community. Upon contamination, soil microbes can display metabolic changes, which can be measured through the profiling of their potential for the oxidation of organic substrates. The present study aimed to evaluate the microbial metabolic profile in soil samples containing different forms of inorganic As (AsIII and AsV) in a 360-day experiment. Soil samples were contaminated with AsIII or AsV (15 mg/kg soil) and the microbial metabolic profile was evaluated after 3, 30, 180, and 360 days of experiment. After these periods, the assay was performed using Biolog Ecoplate™ microplates followed by incubation with readings every 24 h for 5 days. The main parameters evaluated were metabolic activity (AWCD), diversity (Shannon index), and use of substrates containing N or P (NUSE and PUSE). It was observed that the microbial community reacted differently according to the exposure time and for the two contaminants. While metabolic activity decreased in the AsV group ( p = 0.03) in 30 days when compared to the control group, the use of sources containing nitrogen decreased in the AsIII group ( p = 0.01) only after 360 days when compared to the control group. These findings indicate that the soil microbial community suffers a decrease in metabolic activity when exposed to arsenate in short exposures, whereas, in soil with long-term exposure to arsenite, the microbial community suffers a decrease in the consumption of nitrogen-rich substrates.