The turtle holobiont

During my time at TurtleBIOME I worked on elucidating the structure and composition of microbial communities of loggerheads. Loggerhead sea turtles are one of the seven extant sea turtle species and are considered vulnerable by the IUCN. They are threatened by human activity (tourism, fishing, pollution), climate change, and pathogenic microorganisms (Fusarium sp., viral infections, etc.).

First reports on sea turtle/loggerhead microbiomes in the gut were from Abdelrhman et al. in 2016. Since then many research groups around the world have started investigating the microbiomes of loggerheads and other sea turtle species to improve the conservation efforts and understand the microbial impact on the sea turtle host.

In 2021 my group and I published our (Filek et al. 2021) work on cloacal and oral bacterial communities of loggerheads in the Adriatic Sea. The turtles were found injured or caught accidentally by fishermen in the winter months. We confirmed previous findings by other researchers that cloacal microbiomes remain stable during short-term rehabilitation. Further, we reported the first findings related to the oral microbiome which is much more dynamic and reflective of the environment as the first part of the gastrointestinal tract that comes in contact with the environment.

In the meantime, I was also working on research by Kanjer et al. (2022), on the external microbiomes (carapace and skin) of loggerheads sampled in the Adriatic Sea, Ionian Sea, Tyrrhenian Sea and Aegean Sea. This major effort with many collaborations across the Mediterranean resulted in first comprehensive insights into bacterial and microeukaryotic components of the loggerhead microbiome. We found we might distinguish the turtles’ origin based on their surfaces’ highly diverse microbial communities.

Recently, I wrapped up data analyses of microbiotas for a new cohort of loggerheads that were found injured or accidentally caught in the spring/summer months, mostly in the Adriatic Sea. The work was submitted for review in October 2023 and the preprint can be found here. I looked into bacterial communities of oral and cloacal samples in tandem with corresponding carapace samples to get a more detailed image of the Adriatic loggerhead holobiont. In addition to bacteria, I helped my (at the time) master’s student investigate the fungal component of the gut microbiota found in loggerhead cloacas. Reviewer no.2 please be kind!