DISSERTATION RESEARCH: The Influence of Antibiotic Compounds on Soil Microbial and Invertebrate Communities

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The discovery of antibiotics was one of the scientific breakthroughs of the 20st century. While many people are familiar with how antibiotics are used for human health, the vast majority of antibiotics produced today are used to promote the health and growth of livestock. As with many medicines, up to 80% of the total dosage of active antibiotics are eliminated through animal waste, like feces and urine, and introduced to the surrounding environment. Although previous research has found more antibiotic-resistant organisms near livestock farms than generally, scientists do not fully understand how antibiotics coming from livestock waste impact important organisms in soils that are exposed to them: soil microbes, like bacteria and fungi, and invertebrates, like millipedes, pillbugs, spiders and insects. Healthy communities of microbes and invertebrates are responsible for recycling nutrients in soils and making them available to plants and the animals that eat them. This research will help scientists understand how the common practice of adding antibiotics to soils, by applying contaminated livestock manure to crop soils, may be disrupting the nutrient-cycling soil organisms, and how well these organisms can make nutrients available. Through this research, scientists, farmers and the public can promote responsible waste management practices that will help protect our ecosystems and benefit human health. The project will also train a graduate student, and American Indian volunteer researchers.Using antibiotic (tetracycline)-laden manure from cattle, this research will consist of a series of field experiments that assess how antibiotic compounds change decomposition rates in the soil, microbial respiration (an important factor in carbon and nutrient cycling), and microbial and invertebrate community composition. The researcher will also test how the microbiome of invertebrate communities raised on antibiotic-laden manure compares to those raised on untreated manure. This research fills a critical gap in our understanding of three important ecological phenomena: (1) how antibiotics affect community structure of soil microbes and invertebrates, (2) which invertebrate and microbial taxa are most important to decomposition and greenhouse gas emission, and (3) how disrupting invertebrate microbiomes drives mortality in invertebrate communities. Furthermore, by conducting our proposed study at an agricultural field site, we provide insight into what governs the health and function of a globally prominent and economically important ecosystem.