Characterising the role of microbial behaviour and nutrient exchanges in coral symbioses

Coral reefs are the most diverse marine ecosystems, but are currently threatened by anthropogenic stressors that disrupt the relationship between the coral host and its microbial symbionts (i.e., endosymbiotic microalgae and bacteria).

While these symbionts are fundamental to coral health, corals do not generally transmit them to their offspring, who have to acquire them from the environment.

Despite the critical roles of microbial symbionts for coral health, we still do not know how they find and colonise their coral hosts, which key compounds are exchanged between the various partners once in symbiosis, and to what extent bacterial symbionts contribute to coral growth.My previous research has revealed the importance of chemotaxis in other marine symbioses, a behaviour allowing microbes to find their host by homing in on the chemical cues it produces.

Building on my previous research and preliminary data, I hypothesise that coral symbionts also use chemotaxis to find and colonise corals.

Using a unique combination of cutting-edge approaches, this project aims to characterise the onset and functional consequences of coral-microbe symbioses.

More specifically, it will:(1) identify the chemical cues underpinning the recruitment of coral symbionts, using analytical chemistry approaches and in situ chemotaxis assays that I previously developed;(2) determine how key bacterial symbionts colonise their coral host, through genetic engineering of the bacterial symbionts with live imaging and microscopy;(3) characterise the chemical exchanges between bacteria, microalgae, and their coral host, by combining co-culture assays, omics, and high-resolution secondary ion mass spectrometry.By deciphering the chemical language of coral symbiosis, this project will reveal biological processes at the foundation of coral health, a game changer in the current context of widespread reef degradation.