Symbiosis and the holobiont concept

Symbiosis is the close association between two or more organisms of different species. Thanks to technological advances, we now know that all macroorganisms engage in stable and highly-specific associations with microbial communities! Those microbes influence the ecology, development, and function of the host. Thus, animals, plants, and algae cannot longer be considered as single entities but holobionts. The holobiont is a biological organization unit comprised by the host, its associated microbes, and the emerging functions derived from the interactions. That is, the holobiont is more than the sum of its parts! I combine molecular work (e.g. RNA-Seq, amplicon sequencing) with an experimental approach to disentangle the relative role of environment-host-and microbial factors in the functioning of the holobiont. And my focus is on marine sponges.

Why sponges?

Sponges are early-diverging organisms, allowing us to investigate conserved mechanisms in animal evolution. They resulted in one of the more complex marine symbiosis and constitute a source of novel microbial diversity, functions, and natural products. Finally, the host capacity to filter thousands of liters of water per day together with the activity of the microbial partners makes sponge holobionts a key component of the nutrient cycling in the ecosystem.

Nested ecosystems

Holobionts can be regarded as complex ecosystems consisting of the host, the microbiota, and the interactions among them. Applying ecological theory helps us to understand the relative roles of microbial, host-related factors and environment in shaping the symbiotic interactions. Holobionts are further integrated into larger and more complex communities and ecosystems. Like a Russian doll, microbial processes translate into holobiont functions that impact the surrounding environment. And vice versa, environmental perturbations may challenge the outcome of the interactions within the holobiont. Therefore, I am particularly interested in investigating holobiont processes in a relevant ecological context.

Sponge ecological immunology

Research on sponge immunity started more than 100 year ago. Nobel Laureate Metchnikoff investigated sponges in his interest to understand digestion in early-diverging organisms and to develop its phagocytic theory. Others have shown that sponges are able to distinguish self vs non-self. Yet, the molecular mechanisms of sponge immunity remain understudied. My research goals are: to understand sponge immunity in discriminating symbiont vs non-symbiotic microbes, to characterize the immune responses under different contexts (e.g. injury) and environmental conditions, and to identify conserved mechanisms of animal-microbe communication. I hypothesize that the immune system is the guardian of the holobiont by orchestrating host-microbe interactions and keeping homeostasis.


A big support for my current research activities comes from the Collaborative Research Centre 1182-Origin and Functions of Metaorganisms