Loggerhead sea turtle-associated epizoic vs. non-epizoic diatoms

by Klara Filek |

We are happy to share research from our fellow Young ISDR members. Please see below a summary of the interesting research of Klara Filek.

Loggerhead sea turtles carry a vast number of microorganisms on their shells, including diatoms. Some of these diatoms are epizoic (e.g., Achnanthes elongata) and cannot be found in the host’s environment, while others are considered to be non-epizoic opportunists. To date, factors leading to exclusively epizoic lifestyle of diatoms are unknown, nor is it known how the epizoic and opportunist diatoms interact with each other on their host. As we learn more about the diatom component of host microbiota its becoming crucial to decipher the intricacies of this peculiar diatom habitat and way of life.

Within my PhD project I am studying the microbial communities associated with loggerhead sea turtles, including diatom interactions in culture. To investigate the potential dynamics between diatoms that might occur on the turtles’ surfaces I have isolated diatoms from the scrapings of loggerhead sea turtle, established xenic monocultures, and identified them via morphology and sequencing marker genes. Of all isolated diatoms, a known epizoic diatom A. elongata and two non-epizoic Psammodictyon strains were grown together in co-cultures (one strain epizoic with one strain non-epizoic). Their growth and biomass production were followed over 19 days by a high-throughput plate reader generating a massive number of images to analyze. Observing growth changes in epizoic vs. non-epizoic diatoms should provide a first glimpse into whether these diatom taxa affect each other in some way and if the behavior could translate to the sea turtle carapace and skin habitat.

Even though the co-culturing setup cannot fully reflect the complexity of microbial interactions in the wild, it will add to the interpretation of data collected on epizoic diatoms, as well as contribute to generating novel hypotheses about host-associated diatoms’ lifestyle.

Figure description: Time-lapse of Achnanthes elongata and Psammodictyion panduriforme growing in co-culture over 19 days.