Abstract: Bacteria play crucial roles in most of the biogeochemical cycles in the oceans due to their high abundance and metabolic capabilities. Each square centimetre of coral surface harbours between 106 and 108 bacterial cells, ten times more, on average, than the surrounding sea water. These coral-bacteria assemblages tend to be highly specific to their host and include large number of rare and sometimes even unique taxa. Although the phylogenetic diversity and dynamics of coral-associated bacterial communities have been extensively studied for more than a decade, their ecological and functional roles in coral reefs are still poorly understood. Recently, pioneering studies have started to unravel the role of associated bacteria and their interaction with their coral hosts. Some members of the Alphaproteobacteria and Cyanobacteria taxa are likely to fix dissolved nitrogen; a particularly important process in an oligotrophic environment such as coral reefs. Others like Roseobacter and Spongiobacter can metabolize dimethylsulfoniopropionate (DMSP), an organic sulfur compound produced in large amounts by corals and suspected to play an important role in coral-bacteria associations. Bacteria are also likely acting as a line of defence against invasive pathogens, by competing for space and occupying coral niches, or by directly producing antimicrobial compounds, inhibiting the growth of invasive microbes in corals. During this seminar I will present some of the results derived from my PhD, investigating the functional roles played by DMSP-degrading bacteria in corals. Building upon this body of work, a proposed study investigating more exhaustively the functional roles of coral-associated bacteria will be presented, using a combination of genomic, metabolomic, and advanced imaging techniques coupled with culture-based and chemistry approaches. The outcomes of this work would greatly enhance our understanding of the symbiotic relationships that enables the success and persistence of the most productive and biologically diverse marine ecosystem on the planet.

Biography: Jean-Baptiste studied for his PhD under the supervision of Professor Bette Willis (JCU) and Dr David Bourne (AIMS) after being awarded his Bachelor’s degree from the Centre of Oceanography, University of the Mediterranean Sea in Marseille. His research is in the general area of marine microbial ecology. His PhD and Master degrees at JCU have greatly enhanced his knowledge of tropical marine systems and coral microbiology. In particular his PhD research explored the functional role of coral-associated bacteria in the sulfur cycle. He investigated the role of dimethylsulfoniopropionate (DMSP), an organic sulfur molecule produced in large amounts by reef-building corals, in the structure of coral-associated bacterial communities. The interdisciplinary nature of his research enabled him to develop a broad knowledge across various fields.