IMPACT OF CHANGING WASTE STREAMS ON MICROBIAL ECOLOGY AND BIOGEOCHEMICAL CYCLING IN LANDFILL ECOSYSTEMS

Landfills ecosystems contain a wide variety of organic and inorganic materials that fuel microbial processes contributing to diverse biogeochemical cycles. Landfill microbiology is vulnerable to anthropogenic pressures, such as inputs of contaminants of emerging concern (CECs). Increasingly, landfills are becoming reservoirs for discarded pharmaceuticals, which can contribute to the disruption of in situ microbial dynamics and development of antibiotic resistant genes that may potentially affect surrounding populations and ecosystems. To date, however, the impact of CECs on the composition and diversity of landfill microbial communities is poorly understood due to sparse application of modern sequencing techniques. We constructed laboratory-scale landfill microcosms to study the impact of a variety of waste inputs, including antibiotics, sulfur, and iron, on landfill microbial communities. We selected the five most commonly prescribed antibiotics in the United States as well as the two most common antibiotics used in agriculture to add to the microcosms in quantities previously documented in landfill liquids (leachate). Microcosms were sampled for DNA six times over a 65-day period to capture temporal changes in the microbial community. Test inputs (antibiotics, sulfur, and iron) were added after ~40 days and compared to control microcosms without additions. 16S rRNA high-throughput sequencing methods documented changes in microbial diversity associated with specific process conditions. Results show markedly high heterogeneity between triplicate microcosms. Moreover, altering waste inputs slightly can significantly alter the dominant microorganisms present as well as the landfill leachate geochemistry which has important implications for biogeochemical cycling in these subsurface ecosystems.