Justin R. Kaspar, PhD
University of Florida, 2016, Microbiology/Immunology
Dr. Justin Kaspar was born in Bay City, Texas and grew up in Blessing, Texas within Matagorda County. Dr. Kaspar attended Texas A&M University and received a B.S. in Microbiology while receiving training in bacteriology and bacteriophage biology while volunteering in Dr. Ryland Young's lab in the department of Biochemistry and Biophysics. After, Dr. Kaspar received his PhD from the University of Florida College of Medicine Graduate Program in Biomedical Sciences on the Microbiology/Immunology focused track while performing his graduate studies within Dr. Robert Burne's lab in the College of Dentistry. Dr. Kaspar's PhD project involved studying the integration of streptococcal stress tolerance in cell-cell (peptide-based) signaling and received an F31 fellowship from the NIH and NIDCR. Following graduation, Dr. Kaspar remained within the lab of Dr. Robert Burne at the University of Florida College of Dentistry while shifting his research focuses to intermicrobial interactions that occur within the oral supragingival biofilms that was supported with an NIH/NIDCR F32 fellowship.
Dr. Kaspar's research interests center on the microbial interactions that occur within the human oral cavity. Specifically, the lab is exploring physical contact-dependent interactions between early colonizers of supragingival biofilm communities and pathogens such as Streptococcus mutans that drive sequential changes within the microbiome during initial colonization and subsequent biofilm formation. Additionally we have interests in the biogeography or spatial arrangement of bacteria within oral biofilms, how it can be modified and the role of the spatial arrangement in cooperative/antagonistic interactions between bacterial species. Finally, we continue to study Gram-positive bacterial communication in the form of peptide or 'pheromone' signaling through detailing specific pathway(s) in oral streptococci in terms of the gene(s) the peptide signaling systems regulate, their role in bacterial fitness and their effect on the larger bacterial community and/or microbiome.
Bacteria within multispecies communities grow and persist in complex environments by competing over scare resources such as nutrients and physical space. The human oral cavity is ideally suited as a model for the dissection of interspecies interactions. In the human mouth, billions of microbes belonging to over 700 independent taxa function cooperatively and/or antagonistically to shape the composition of the microbiome. These interactions, coupled with frequent environmental perturbations, can also disrupt microbial homeostasis; which can lead to the ecological shifts observed during development of oral diseases. For example, as is the case for dental caries, increases in the proportions of strongly acidogenic and acid tolerant bacteria, such as the mutans streptococci, are observed when bacterial fermentation of dietary carbohydrates repeatedly acidifies microbial biofilms, leading to demineralization of the tooth. Concurrently, health-associated commensal streptococci, which are less constitutionally resistant to low pH, decrease in proportions. Loss of these species compounds the problem as many of these commensal streptococci provide protection from caries development by metabolizing arginine via the arginine deiminase system (ADS), which elevates the pH through release of ammonia. Further, many commensal streptococci can directly inhibit growth and/or expression of virulence traits by mutans streptococci through multiple strategies; with the generation of hydrogen peroxide being a significant deterrent to growth of Streptococcus mutans and other oral pathogens. Research within the Kaspar Lab focuses on dissecting how S. mutans responds to health-associated oral Streptococcus species that occupy the same niche and how these responses may be modulated for development of novel therapeutic approaches.
Kaspar JR, Lee K, Richard B, Walker AR, Burne RA. Direct interactions with commensal streptococci modify intercellular communication behaviors of Streptococcus mutans. ISME J. 2020 Sep 30;. doi: 10.1038/s41396-020-00789-7. [Epub ahead of print] PubMed PMID: 32999420. https://pubmed.ncbi.nlm.nih.gov/32999420/
Lee K, Walker AR, Chakraborty B, Kaspar JR, Nascimento MM, Burne RA. Novel Probiotic Mechanisms of the Oral Bacterium Streptococcus sp. A12 as Explored with Functional Genomics. Appl Environ Microbiol. 2019 Nov 1;85(21). doi: 10.1128/AEM.01335-19. Print 2019 Nov 1. PubMed PMID: 31420345; PubMed Central PMCID: PMC6803316.
Shields RC, Kaspar JR, Lee K, Underhill SAM, Burne RA. Fluorescence Tools Adapted for Real-Time Monitoring of the Behaviors of Streptococcus Species. Appl Environ Microbiol. 2019 Aug 1;85(15). doi: 10.1128/AEM.00620-19. Print 2019 Aug 1. PubMed PMID: 31101614; PubMed Central PMCID: PMC6643251.
Kaspar JR, Godwin MJ, Velsko IM, Richards VP, Burne RA. Spontaneously Arising Streptococcus mutans Variants with Reduced Susceptibility to Chlorhexidine Display Genetic Defects and Diminished Fitness. Antimicrob Agents Chemother. 2019 Jul;63(7). doi: 10.1128/AAC.00161-19. Print 2019 Jul. PubMed PMID: 31036688; PubMed Central PMCID: PMC6591629.
Kaspar JR, Walker AR. Expanding the Vocabulary of Peptide Signals in Streptococcus mutans. Front Cell Infect Microbiol. 2019;9:194. doi: 10.3389/fcimb.2019.00194. eCollection 2019. Review. PubMed PMID: 31245303; PubMed Central PMCID: PMC6563777.
Kaspar J, Shields RC, Burne RA. Competence inhibition by the XrpA peptide encoded within the comX gene of Streptococcus mutans. Mol Microbiol. 2018 Aug;109(3):345-364. doi: 10.1111/mmi.13989. Epub 2018 Jul 31. PubMed PMID: 29802741; PubMed Central PMCID: PMC6158096.
Kaspar J, Underhill SAM, Shields RC, Reyes A, Rosenzweig S, Hagen SJ, Burne RA. Intercellular Communication via the comX-Inducing Peptide (XIP) of Streptococcus mutans. J Bacteriol. 2017 Nov 1;199(21). doi: 10.1128/JB.00404-17. Print 2017 Nov 1. PubMed PMID: 28808131; PubMed Central PMCID: PMC5626963.
Kaspar J, Kim JN, Ahn SJ, Burne RA. An Essential Role for (p)ppGpp in the Integration of Stress Tolerance, Peptide Signaling, and Competence Development in Streptococcus mutans. Front Microbiol. 2016;7:1162. doi: 10.3389/fmicb.2016.01162. eCollection 2016. PubMed PMID: 27516759; PubMed Central PMCID: PMC4963387.
Kaspar J, Ahn SJ, Palmer SR, Choi SC, Stanhope MJ, Burne RA. A unique open reading frame within the comX gene of Streptococcus mutans regulates genetic competence and oxidative stress tolerance. Mol Microbiol. 2015 May;96(3):463-82. doi: 10.1111/mmi.12948. Epub 2015 Mar 4. PubMed PMID: 25620525; PubMed Central PMCID: PMC4414889.