Date Approved


Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School


Committee Member

Paul Price, PhD

Committee Member

Aaron Liepman, PhD

Committee Member

Daniel Clemans, PhD


The rise of infections caused by antibiotic resistant bacteria, compounded by a reduction in antibiotic discovery and development, jeopardizes human health. Historically, antibiotics derive from secondary metabolites produced by soil microbes in pure culture, but recent genetic evidence suggests that microbes can produce more secondary metabolites than are currently observed. The modified crowded plate technique directly identifies antibiotic-producing soil microbes that were co-plated with a target pathogen. Here, this technique was refined by testing the effect of a D-alanine auxotrophic target pathogen rather than a prototrophic pathogen as well as investigating conditions most conducive to antibiotic production. Antibiotic producing conditions are most favorable with the use of a D-alanine auxotrophic pathogen that was pre-incubated for one week. Antibiotic-producing microbes isolated using these new parameters were cultured in single and mixed fermentations to compare secondary metabolite production. Furthermore, mixed fermentations with multiple antibiotic producers is an effective means to stimulate antibiotic production.