Ass.-Prof. Dr. Jillian Petersen

Assistant Professor
WWTF Vienna Research Group Leader
University of Vienna
Althanstr. 14
A-1090 Vienna
Phone: +43 1 4277 91206

Our Research:

Every animal, including humans, evolved in a ‘sea’ of microbes. Animal-microbe mutualisms are ubiquitous in nature and are powerful driving forces in the evolution of life on Earth. Most animal-associated microbial communities are enormously diverse, which poses an immense challenge to understanding the molecular crosstalk that underpins establishment and maintenance of these lifelong partnerships. Many marine invertebrates have evolved intimate associations with just one or a few species of chemosynthetic bacteria. They are therefore ideal natural models for investigating the fundamental mechanisms that underpin host-microbe associations.

400 Million Years of Symbiosis: Marine Lucinid Clams and their Sulfur-oxidizing Symbionts

We investigate host-microbe mutualisms in lucind clams that host a specific species of sulfur-oxidizing bacteria in their gill cells (the symbionts are shown in red, left). Lucinid clams are found worldwide in shallow marine habitats such as coastal seagrass sediments that are easily accessible for sampling. There are hundreds of species of lucinids currently known, and almost every one of these hosts its own specific symbiotic microbes. The symbiotic bacteria are chemosynthetic, which means they use chemical energy from the environment to synthesize sugars and other molecules needed by the host. This ancient and highly successful partnership has resulted in a reduction of the length and complexity of the clam’s digestive tract over evolution, as it relies on its gill symbionts for nutrition.


Current projects:

Molecular host-microbe crosstalk. Molecular host-microbe crosstalk is the language used by symbiotic partners to recognize and communicate with one another. The innate immune system of bivalves allows them to interact specifically with their symbionts and to tell them apart from the diverse 'crowd' of bacteria in their environment. Many beneficial microbes use similar molecular mechanisms to communicate with their hosts as pathogenic microbes use to ‘hijack’ their hosts. How these mechanisms evolved, and which factors determine whether they will be used for ‘good’ or ‘evil’ is currently not well understood. Our approach uses field experiments and laboratory experiments in aquaria at the University of Vienna. The goal of our work is to better understand of the molecular basis of beneficial host-microbe associations.

Fine-scale microbial diversity and the individuality of the microbiome. Fine-scale diversity in bacteria is the diversity seen within traditionally accepted species boundaries. Recent studies have revealed a remarkable diversity of microbes in nature, and have provided insights into how fine-scale diversity emerges and how it is maintained in natural populations. Investigating the fine-scale diversity of host-associated microbes have revealed the remarkable individuality of these microbes, meaning that each individual animal, including each human being, hosts its own genetically unique microbiome. The next challenge is to understand how microbial fine-scale genetic diversity affects their function. Our research therefore relies on state-of-the-art techniques for quantifying microbial activity in nature. Our goal is to understand the role of fine-scale diversity in the functioning and evolutionary stability of host-microbe associations.


We have aquaria to keep lucinids in our lab in Vienna. We also work in the field at multiple locations in Europe, the Caribbean, and Africa.





Our work is funded by the Vienna Science and Technology Fund, European Research Council, the Austrian Academy of Sciences and the Region Guadeloupe.