Here you will find information about the research publications that have come out of the Kaspar Lab @ The Ohio State University College of Dentistry. We’ve had numerous lab members involved in a variety of different projects since we first started back in 2020, and are proud to showcase their hard work with the list of publications below.

Visit a complete list on PubMed

A. Choi, K. Dong, E. Williams, L. Pia, J. Batagower, P. Bending, I. Shin, D.I. Peters,  and J.R. Kaspar

The bacteria within supragingival biofilms participate in complex exchanges with other microbes inhabiting the same niche. One example is the mutans group streptococci (Streptococcus mutans), implicated in the development of tooth decay, and other health-associated commensal streptococci species. Previously, our group transcriptomically characterized intermicrobial interactions between S. mutans and several species of oral bacteria. However, these experiments were carried out in a medium without human saliva. To better mimic their natural environment, we first evaluated how inclusion of saliva affected growth and biofilm formation of eight Streptococcus species individually and found saliva to positively benefit growth rates while negatively influencing biofilm biomass accumulation and altering spatial arrangement. These results carried over during evaluation of 29 saliva-derived isolates of various species. Surprisingly, we also found that addition of saliva increased the competitive behaviors of S. mutans in coculture competitions against commensal streptococci that led to increases in biofilm microcolony volumes. Through transcriptomically characterizing mono- and cocultures of S. mutans and Streptococcus oralis with and without saliva, we determined that each species developed a nutritional niche under mixed-species growth, with S. mutans upregulating carbohydrate uptake and utilization pathways while S. oralis upregulated genome features related to peptide uptake and glycan foraging. S. mutans also upregulated genes involved in oxidative stress tolerance, particularly manganese uptake, which we could artificially manipulate by supplementing in manganese leading to an advantage over its opponent. Our report highlights observable changes in microbial behaviors through leveraging environmental- and host-supplied resources over their competitors.

Growth with Commensal Streptococci Alters Streptococcus mutans Behaviors

Journal of Dental Research, Volume 102, Issue 4 (2023)

M. Rose, N. Wilson, E. Williams, H. Letner, R. Bettinger, A. Bouchendouka, J. Batagower, and J.R. Kaspar

As oral bacteria grow and persist within biofilms attached to the tooth’s surface, they interact with other species to form synergistic or antagonistic exchanges that govern homeostasis for the overall population. One example are the interactions between the cariogenic species Streptococcus mutans and oral commensal streptococci. Previously, we showed that the cell–cell signaling pathways of S. mutans were inhibited during coculture with other oral streptococci species, leading us to posit that the S. mutans transcriptome and behaviors are broadly altered during growth with these species. To test this hypothesis, we performed whole transcriptome sequencing (RNA-seq) on cocultures of S. mutans with either Streptococcus gordoniiStreptococcus sanguinis, or Streptococcus oralis and a quadculture containing all 4 species in comparison to S. mutans grown alone. Our results reveal that in addition to species-dependent changes to the S. mutans transcriptome, a conserved response to oral streptococci in general can be observed. We monitored the behavior of S. mutans by both microscopy imaging of biofilms and in a bacteriocin overlay assay and verified that S. mutans acts similarly with each of these species but noted divergences in phenotypes when cocultured with another cariogenic Streptococcus (Streptococcus sobrinus) or with oral non-streptococci species. RNA-seq with oral non-streptococci showed lack of a consistent gene expression profile and overlap of differentially expressed genes found with commensal streptococci. Finally, we investigated the role of upregulated S. mutans genes within our data sets to determine if they provided a fitness benefit during interspecies interactions. Eleven total genes were studied, and we found that a majority impacted the fitness of S. mutans in various assays, highlighted by increased biomass of commensal streptococci in mixed-species biofilms. These results confirm a common, species-independent modification of S. mutans behaviors with oral commensal streptococci that emphasizes the need to further evaluate oral bacteria within multispecies settings.

Microbiology Resource Announcements (ASM), Volume 10, No. 35 (2021)

Justin R. Kaspar

Streptococcus oralis is an early colonizer and one of the most abundant species found in the human oral cavity. We report the complete genome sequence of S. oralis 34 (1,920,884 bp; GC content, 41.3%), commonly used in many oral microbiology studies exploring bacterial attachment and interaction(s) within mixed-species model systems.


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