S179: Tracking the impacts of arsenic contamination on soil microbial communities with GeoChip

Functional gene arrays such as GeoChip have been demonstrated to be a powerful tool for understanding microbial community composition, structure, function, and dynamics and linking microbial communities with environmental factors and ecosystem functioning. Based on previous GeoChips, we have developed GeoChip 4.0, a more comprehensive GeoChip to facilitate our analysis of microbial communities from a variety of habitats. GeoChip 4.0 contains more than 135,000 probes from 152,000 genes involved in C, N, S and P cycling, organic contaminant degradation, metal resistance, antibiotic resistance, stress responses, metal resistance, virulence, bacterial phage-mediated lysis, and soil beneficial microorganisms. We have successfully used GeoChips to analyze samples from a variety of environments, including samples from arsenic contaminated soils. Our results indicate that microbial metabolic potential and diversity were decreased with soil depths in the contaminated sites. Significant variability of key microbial functional genes related to arsenic resistance, carbon and nitrogen metabolism were also observed across different soil depths. The C:N showed significant correlations with arsC/B/A (p = 0.069), carbon cycling (p = 0.084) and nitrogen fixation genes (p = 0.024). The combination of P, NO₃^- and C:N showed the highest correlation (p = 0.062, r = 0.779) with the whole microbial community functional structures. Our results revealed that a long-term (16 years) arsenic downward infiltration had impacts on functional gene distribution, while available nutrient and spatial isolation were the key factors in shaping community structures/functions and controlling arsenic transformation. Such knowledge will be essential for future protection of biodiversity and arsenic remediation.