Photosymbiosis

Photosymbioses between heterotrophic hosts and photosynthetic endosymbionts are ubiquitous in oligotrophic marine environments and an important driver of global nutrient cycles. Throughout evolutionary history, these symbioses have independently developed on numerous occasions. Yet, the rapid environmental change of the Anthropocene is now destabilizing these associations at a global scale.

In the newly established Photosymbiosis Focus Group, our mission is to unravel the mechanisms behind the evolutionary success and the current ecological collapse of photosymbioses. We employ cutting-edge imaging and omics technologies to investigate the processes involved in the development, maintenance, and breakdown of these intricate relationships.

Our research centers around three interlinked areas:

1) Characterize the metabolic controls of symbiotic interactions

Resource competition between the host and symbiont could be key in stabilizing the efficient recycling of nutrients in the symbiosis. The formation of mutualistic interactions could thus be an emerging property of symbiotic associations in nutrient-limited environments.

2) Resolve the interplay of symbiont nutrient release and host immunity

The release of photosynthetic nutrients might allow algae to survive within the host by mimicking active digestive processes. Understanding this link between photosynthesis and symbiosis stability could shed light on the repeated evolution of photosymbioses and their vulnerability to climate change, as exemplified by coral bleaching.

3) Understand the drivers of co-evolution towards obligate symbiotic interactions

The inherent instability of photosymbioses could favor their evolution towards obligate associations in variable environments. Resolving the ecological tradeoffs between facultative and obligate metabolic interactions could help us understand fundamental processes enabling the formation of organelles such as the chloroplast.