Freiburg researchers study oral bacteria in periodontitis

Dental Tribune International

Tue. 16. December 2025

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FREIBURG, Germany: Thousands of different bacteria colonise the oral cavity, many of which remain unidentified. Researchers in Freiburg are now using a combined culture- and gene-based approach to determine which of these microorganisms contribute to periodontitis. The project, funded by the German Research Foundation, combines two methods that have been used successfully in gut microbiome research to analyse both the genetic material and the culturable bacteria. The aim is to gain a more precise understanding of how the composition of the oral microbiota differs between various states of health and periodontitis.

“We want to better understand the diversity of bacteria in the mouth and specifically cultivate species that were previously only known by their gene sequence,” Prof. Ali Al-Ahmad, project leader and laboratory head of the Department of Operative Dentistry and Periodontology at the Medical Centre—University of Freiburg, said in a press release. Earlier this year, the researchers identified a new bacterial species, Dentiradicibacter hellwigii, in a human root canal. This finding underscores how much of the microbial world of the oral cavity remains unexplored.

For the project, the researchers are collecting samples from the oral cavities of patients with and without periodontitis. The bacteria are cultivated on a wide range of growth media in a process known as culturomics. At the same time, the genetic material of the bacteria is analysed. This combination of cultivation-based and genetic approaches has so far been used primarily to characterise the gut microbiome and has led to the isolation of many previously unknown bacterial species.

“There are still many bacteria in the mouth that we don’t know whether they protect us or make us ill. This project is an important step towards shedding light on this issue,” said Prof. Fabian Cieplik, a medical director in the same department. Ultimately, a clearer picture of the oral microbiota—including species that have so far remained unknown—could pave the way for earlier diagnosis and more individualised prevention and treatment strategies for periodontal diseases.

From left: Profs. Ali Al-Ahmad and Fabian Cieplik are part of a scientific team investigating the oral microbiota to identify which bacteria are involved in periodontal diseases.