# Probing Respiration and Metabolism of a Periodontal Pathogen

> **NIH NIH F31** · GEORGIA INSTITUTE OF TECHNOLOGY · 2022 · $47,552

## Abstract

Project Summary
Periodontitis is a highly prevalent disease affecting nearly half of all American adults, and if left untreated leads
to bone loss and tissue damage [1]. Multiple microbes are associated with this disease [2, 3] and through
chemically-mediated interactions form complex interspecies communities within the periodontal crevice. Due to
the complexity of these chemically-mediated interactions, periodontitis remains a difficult disease to treat. Efforts
using polymicrobial communities [4, 5] and animal models [5, 6] have explored possible chemical interactions
and have greatly advanced our understanding of the chemical interactions occurring during periodontitis. In the
Whiteley lab we use a two-species model system composed of Streptococci gordonii (Sg), a representative
Gram-positive streptococcal species capable of consuming sugars and producing acids such as L-lactate as well
as producing hydrogen peroxide (H2O2), and Aggregatibacter actinomycetemcommitans (Aa), a Gram-negative
oral pathogen associated with aggressive periodontitis. Previously, we have shown that when grown in co-
culture, Sg cross-feeds Aa its preferred carbon source, L-lactate, while additionally providing the social cue H2O2
thereby enhancing the fitness of Aa [7-9]. By being cross-fed L-lactate, the slow-growing Aa is able to better
compete within a polymicrobial environment. Furthermore, H2O2 serves as a cue by stimulating the production
of the complement factor ApiA that protects Aa from complement killing [4], and induces the production of the
protein Dispersin B that allows Aa to control its spatial localization [9]. In addition to these fitness benefits, we
also hypothesize based on previous data that Sg-produced H2O2 also serves as a direct source of O2 for Aa
through catalase mediated detoxification [8]. While L-lactate and H2O2 have been shown to provide important
metabolic cues for Aa, recent genomic work indicates that there are likely additional chemical interactions
occurring between these bacteria during co-infection [8, 10]. Our hypothesis is that Aa displays defined
responses to Sg that are critical to establishing precise spatially structured biofilms at the micron scale.
The first objective of the project is to test the hypothesis that Aa can use O2 derived from H2O2 detoxification as
evidenced by a shift in respiration when Aa is grown in co-culture with Sg, and how H2O2 impacts spatial
structure. In the second objective we will use mass spectrometry to develop a comprehensive understanding of
the chemical interactions occurring between Aa and Sg. The results from these studies will provide direct insight
into the processes underlying the additional benefits Aa receives through H2O2 detoxification. By identifying the
unknown chemical interactions between Aa and Sg, we can better understand the complex interspecies
interactions involved in periodontitis.

## Key facts

- **NIH application ID:** 10336346
- **Project number:** 5F31DE029415-03
- **Recipient organization:** GEORGIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Alexander Klementiev
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $47,552
- **Award type:** 5
- **Project period:** 2020-01-01 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10336346

## Citation

> US National Institutes of Health, RePORTER application 10336346, Probing Respiration and Metabolism of a Periodontal Pathogen (5F31DE029415-03). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10336346. Licensed CC0.

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