Acid Tolerance and Resistance to Oxidative Stress in Oral Bifidobacterium and Streptococcus Species
Board Location: #12
Discipline: Biological Sciences
Subcategory: Microbiology/Immunology/Virology
Session: 2
Ashley Rojas Romero - Indiana University South Bend
Bifidobacterium is a genus of beneficial bacteria that primarily reside in the human gastrointestinal tract, but some species have also been found in the oral cavity. One such species, Bifidobacterium dentium, has been found not only in the intestines but in dental caries as well. Compared to other narrow-range intestinal bifidobacterial species, B. dentium produced a high level of polyphosphate granule (PolyP) in sucrose, even under reducing conditions. We hypothesize that its PolyP-producing ability could contribute to its resistance to oxidative stress and acidic pH in the oral cavity. This hypothesis was tested in three species: B. dentium, Bifidobacterium longum (intestine-only), and Streptococcus mutans (a common cariogenic pathogen). Culture media were designed to mimic oral cariogenic conditions, such as the use of sucrose (“table sugar”), and calcium phosphate (the major component of tooth enamel). Acid-tolerance and oxidative stress experiments were carried out in these three organisms. Results indicated B. dentium had a higher acid tolerance than B. longum and S. mutans under both PolyP-producing and non-producing conditions. The granule-producing cells of B. dentium and B. longum were also more acid-resistant than the non-granule-producing cells. The two bifidobacterial species also demonstrated a greater resistance to hydrogen peroxide under granule-producing conditions. S. mutans, an aerotolerant species, was the most resistant to hydrogen peroxide. We concluded that the high-level granule production in B. dentium might contribute to its survival in unfavorable environments outside the intestines. Future research should focus on developing more accurate methods to quantify granule production and conducting additional experiments to further validate our findings.
Funder Acknowledgement(s): Funded by the Louis Stokes Alliances for Minority Participation (award number EES 2308500)
Faculty Advisor: Yilei Qian, Faculty Advisor, Associate Professor of Microbiology, Department of Biological Sciences, yilqian@iu.edu
Role: I contributed to the design and execution of experiments under the mentorship of my microbiology professor, Dr. Qian. I helped develop culture media simulating oral conditions, performed assays to assess acid tolerance and oxidative stress in B. dentium, B. longum, and S. mutans, and analyzed the results. My work focused on investigating the role of polyphosphate granules in promoting B. dentium survival outside the intestines, with ongoing discussions and guidance from Dr. Qian throughout the project.