Discipline: Biological Sciences
Bryan Sierra-Rivera - California State University, Monterey Bay
Co-Author(s): Dr. Gregoory C. Palmer, The University of Texas at Austin
One of the biggest challenges in the medical industry is the increase of antibiotic resistance among pathogenic bacteria. There is a need to increase production of known antibiotics as well as inducing the production of antibiotics that currently don’t exist. Streptomyces, a genus of bacteria that reside in the soil which are the major source of antibiotics. In a previous study, by Matthew Traxler and colleagues, interspecies interactions of Streptomyces coelicolor with five different actinomycetes grown in co-culture lead to the production of different secondary metabolites that S. coelicolor had not been known to produce in mono-culture. This suggests that chemical cooperation between actinomycete bacteria leads to shifts in secondary metabolite production. Many of the bacteria that induced secondary metabolite production in S. coelicolor produce antibiotics, and it is possible that antibiotics themselves could induce secondary metabolite production in cross-species communication. A strain of Streptomyces was isolated from a soil sample acquired at the University of Texas at Austin campus, the strain was identified by amplification and sequencing of the isolates’ 16S rRNA genes. Nucleotide sequences were identified using BLAST with the results showing the strain being Streptomyces osmaniensis. This organism showed antimicrobial activities against Pseudomonas when tested using Kirby Bauer disk assays. This project tested whether antibiotics could be a mechanism by which interspecies interactions induce antibiotic production. To determine if antibiotic production by one species could increase antibiotic production in a second species in co-culture, the inhibitory effects of ethyl acetate extracts from whole co-cultures were compared to that of mono-cultures against a strain of Pseudomonas. Interestingly, extracts from co-cultures of Streptomyces osmaniensis with Streptomyces coelicolor, wild-type and a non-antibiotic producing mutant, produced statistically significantly smaller zones of inhibition compared to S. osmaniensis grown in mono-culture. The zones of inhibition were also significantly smaller for extracts from co-cultures with S. coelicolor wild-type, indicating that co-culture with an antibiotic-producing organism can be inhibitory for secondary metabolite production in this isolate. These results suggest that antibiotics are not mediators of enhanced secondary metabolite production that is often observed in co-culture experiments.Not Submitted
Funder Acknowledgement(s): 1.Summer Undergraduate Program for Experiential Research - (SUPER) 2017 program 2. Institute for Cellular and Molecular Biology, Department of Molecular Biosciences, and the College of Natural Science at the University of Texas at Austin 3. Undergraduate Opportunities Center (UROC) at California State University, Monterey Bay 4. The U.S. Department of Education - (#P031C11021: Hispanic-Serving Institutions STEM Program to develop and carry out activities to improve and expand the institution's capacity to serve Hispanic and other low-income students); the National Science Foundation (NSF) under grant #HRD-1302873 5.Chancellor's Office of the California State University.
Faculty Advisor: Dr. Gregory C. Palmer, email@example.com
Role: Isolation of Streptomyces osmaniensis from soil on the campus of the University of Texas at Austin. Grew liquid cultures and agar plates of mono- and co-cultures of Streptomyces osmaniensis, Streptomyces coelicolor (wild-type), and Streptomyces coelicolor (mutant). 16s rRNA amplification and sequencing. Kirby-Bauer disk diffusion assays using cultures/live cells and ethyl acetate extraction. Calculates stats for zones of inhibition.