SOIL MICROBIOLOGY Resource Amendments Influence Density and Competitive Phenotypes of Streptomyces in Soil

Abstract Carbon from plant rhizospheres is a source of energy for soil microbial communities in native habitats. Soil amendments have been used as a means for deliber-ately altering soil community composition in agricultural soils to enhance plant health. However, little information is available in agricultural or natural soils on how specific carbon compounds or quantities influence soil microbial communities. Streptomyces are important soil saprophytes noted for their ability to produce antibiotics and influence plant health. To explore how specific types and amounts of carbon compounds influence Streptomyces in soil, glucose, cellulose, and lignin were added alone and in combination with six other carbon substrates of varying complexity to mesocosms of native prairie soil for 9 months at amounts equivalent to natural inputs from plants. Estimated cultur-able population densities, antibiotic inhibitory phenotypes, and resource utilization profiles were examined for Strep-tomyces communities from each treatment. The type and quantity of carbon compounds influenced densities, pro-portions, antibiotic phenotypes, and substrate utilization profiles of Streptomyces. Cellulose and lignin inputs produced the largest Streptomyces densities. Also, Strepto-myces communities receiving high-resource inputs were more inhibitory whereas those receiving low-resource inputs used substrates more efficiently. Knowledge of how the availability and quantity of particular carbon com-pounds influences Streptomyces communities and their function, specifically resource use and inhibitory pheno-types, may be helpful in understanding the roles of resource availability in Streptomyces community dynamics and the potential of Streptomyces to suppress pathogens and enhance plant fitness in native and agricultural soils