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Carbon amendments alter nutrient use and pathogen-suppressive potential of soil Streptomyces

Jose Pablo Dundore-Arias: Department of Plant Pathology/University of Minnesota

<div>Organic matter inputs are a common practice for increasing soil microbial activity and biomass in agricultural fields, and can play an important role in disease management. The specific selective impacts of carbon amendments on microbial species interactions and metabolic capacities are not well understood. We investigated the effects of soil carbon amendments on nutrient use and antibiotic inhibitory profiles of <em>Streptomyces </em>in agricultural soils<em>.</em> Soil mesocosms were established in sterile jars (500 g soil/jar), and amended at intervals over nine months with glucose, fructose, a nutrient mixture or no nutrient. Over 130 <em>Streptomyces</em> isolates were collected from amended and non-amended mesocosm soils, and nutrient utilization profiles on 95 different carbon substrates were determined using Biolog SF-P2 plates. A subset of isolates (n = 40) was characterized for their ability to inhibit one another. Carbon amendments were found to expand niche width, growth efficiency, and niche overlap among soil <em>Streptomyces</em>. Carbon inputs also increased the frequency, but reduced the intensity of inhibitory interactions among soil <em>Streptomyces</em>. These results suggest that carbon amendments to soil may intensify competition for preferred resources and enrich antagonistic phenotypes. Thus, the selective impacts of carbon amendments on soil microbiomes may contribute to the establishment of pathogen-suppressive soils in agricultural systems.</div>