Abstract
Arsenic (As) contamination in soil and groundwater has become a serious problem to public health. To examine how microbial communities and functional genes respond to long-term arsenic contamination in vertical soil profile, soil samples were collected from the surface to the depth of 4 m (with an interval of 1 m) after 16-year arsenic downward infiltration. Integrating BioLog and functional gene microarray (GeoChip 3.0) technologies, we showed that microbial metabolic potential and diversity substantially decreased, and community structure was markedly distinct along the depth. Variations in microbial community functional genes, including genes responsible for As resistance, carbon and nitrogen cycling, phosphorus utilization and cytochrome c oxidases were detected. In particular, changes in community structures and activities were correlated with the biogeochemical features along the vertical soil profile when using the rbcL and nifH genes as biomarkers, evident for a gradual transition from aerobic to anaerobic lifestyles. The C/N showed marginally significant correlations with arsenic resistance (p = 0.069) and carbon cycling genes (p = 0.073), and significant correlation with nitrogen fixation genes (p = 0.024). The combination of C/N, NO3 − and P showed the highest correlation (r = 0.779, p = 0.062) with the microbial community structure. Contradict to our hypotheses, a long-term arsenic downward infiltration was not the primary factor, while the spatial isolation and nutrient availability were the key forces in shaping the community structure. This study provides new insights about the heterogeneity of microbial community metabolic potential and future biodiversity preservation for arsenic bioremediation management.
Highlights
Arsenic (As) contamination of soil and water has become a serious problem due to its widespread distribution and high toxicity [1]
Our results revealed that the microbial diversity, structure, metabolic potential, and key functional genes varied greatly along the vertical soil profile, and that the nutrient availability and spatial isolation could be key factors in shaping the soil microbial community structure
The average metabolic response (AMR) values decreased strongly with the soil depth, and the carbon metabolic diversity was much higher in the surface (0-m) samples than those of the other samples (Fig. 1), indicating that the carbon metabolic potential was negatively correlated with depth
Summary
Arsenic (As) contamination of soil and water has become a serious problem due to its widespread distribution and high toxicity [1]. Natural As-contaminated groundwater has been reported all over the world [2,3,4], and this contamination has become a major threat to public health. Chronic drinking of As-contaminated groundwater has caused endemic arsenicosis [5], and As-contaminated soils have resulted in an accumulation of As in rice grains [6]. In order to remediate the Ascontaminated soil, Pteris vittata, an As hyperaccumulating plant, was planted in area of Chenzhou, China, where the soil was contaminated by an adjacent arsenic smelting. We found that the rhizosphere of P. vittata harbored special microbial structures and genes [7]. The downward infiltration of arsenic has caused serious groundwater contamination in the adjacent untreated area, while the response of underground microbial communities and their interactions during this process are largely unknown
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