Abstract

With antibiotic resistance on the rise, researchers are eager to maximize natural product discovery to find novel antibiotic compounds. One way to do this is through high-throughput liquid culture screening of bacterial libraries. Co-culture methods have proven successful in stimulating the expression of silent genes which can trigger the production of compounds that are not produced in monoculture. This expression is caused through the simulation of a competitive environment among the bacterial strains under the stress of minimal media conditions. Using this ecological theory, a more natural environment for bacterial cultivation can be created in the laboratory to maximize the production of novel compounds. We hypothesize that maintaining minimal media conditions and increasing the number of bacteria in culture together (tri-culture and multi-cultures) will further stimulate the production of novel natural products that would not be expressed in monoculture or in co-culture. Prior work has been done in the Wolfe laboratory to assess the antimicrobial activity of compounds produced by soil bacteria isolated from Western NC garden soil in both monoculture and co-culture using 96-well high throughput assay technique. This work expands the utility of this technology by developing a quantitative and robust method for screening microbial cultures encompassing three bacterial strains. Furthermore, during this screening study, it was found that the tri-culture of soil bacteria 540, 442, and 657 showed strong inhibition against S. aureus. To determine the nature of this antibiotic activity, a multi-liter liquid culture scale-up method was developed to maximize the antibiotic secondary metabolites produced by this culture. Antibiotic compounds isolated using this method are then purified using organic techniques and compound characterization can commence.

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