Coaggregation with Actinomyces naeslundii Induces Polarized Filamentation and Cell Division Gene Expression in Corynebacterium matruchotii

Author

• Thet T. Hnin, University at Albany, State University of New YorkFollow

ORCID

https://orcid.org/0009-0000-5223-0447

Date of Award

Summer 2026

Language

English

Embargo Period

7-14-2028

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Biological Sciences

Program

Biology

First Advisor

Alex Valm

Committee Members

Alex Valm, Melinda Larsen, ChangHwan Lee, Jon Paczkowski

Keywords

dental plaque biofilm, bacterial coaggregation, Corynebacterium matruchotii, Actinomyces naeslundii, biofilm architecture, filamentation

Subject Categories

Bacteriology | Biology | Microbial Physiology | Microbiology | Organismal Biological Physiology

Abstract

Human dental plaque is a highly organized polymicrobial biofilm in which interspecies biochemical and physical interactions govern community assembly and emergent properties. Disruption of this organizational balance contributes to oral diseases, including dental caries and periodontitis. Filamentous Corynebacterium species are abundant members of supragingival plaque and are thought to contribute to biofilm architecture by serving as structural scaffolds for complex multispecies arrangements, such as “corn-cob” structures. However, the physiological and molecular consequences of interactions between Corynebacterium and early colonizing species remain incompletely understood. The goal of this study was to determine how coaggregation with the early colonizer Actinomyces naeslundii influences the morphology, gene expression, and spatial organization of Corynebacterium matruchotii. Using quantitative coaggregation assays and live-cell imaging, we demonstrate that C. matruchotii preferentially associates with A. naeslundii, with binding occurring along specific regions of the filament. This interaction is accompanied by a pronounced morphological transition characterized by filament elongation and the formation of spatially organized “spider-web”–like growth structures. To investigate the molecular basis of this response, we performed dual RNA sequencing and identified a coaggregation-associated transcriptional program in C. matruchotii, involving differential expression of 192 genes. Notably, coaggregation with A. naeslundii is associated with upregulation of cell division and growth-associated genes (ftsK/eccC and minD) and downregulation of the division inhibitor sulA and the chromosome organization gene scpA. These transcriptional changes are consistent with the observed morphological phenotype and suggest modulation of the cell division program during interspecies interaction. To assess whether these patterns are recapitulated in situ, we performed spatial transcriptomic analysis using mRNA fluorescence in situ hybridization (FISH) on semi-intact dental plaque samples. This analysis revealed that expression of ftsK/eccC and minD is spatially heterogeneous and correlates with proximity to Actinomyces and Streptococcus populations within the biofilm. These findings support the idea that gene expression in C. matruchotii is influenced by local cellular context within the plaque community. Together, these results demonstrate that coaggregation between C. matruchotii and A.naeslundii is associated with coordinated changes in morphology, gene expression, and spatial organization. This work supports a model in which physical interaction between early colonizing species contributes to biofilm development not only through structural association but also through regulation of cellular behavior, providing new insight into the mechanisms underlying the organization of supragingival plaque.

License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Recommended Citation

Hnin, Thet T., "Coaggregation with Actinomyces naeslundii Induces Polarized Filamentation and Cell Division Gene Expression in Corynebacterium matruchotii" (2026). Electronic Theses & Dissertations (2024 - present). 502.
https://scholarsarchive.library.albany.edu/etd/502