A. Kimberley Lema1,2, Bette L. Willis1, and David G. Bourne2
1ARC Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia ([email protected]
; [email protected]
2Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville 4810, Australia ([email protected]
Scleractinian corals live in a close symbiotic relationship with a diverse group of dinoflagellates (Symbiodinium or zooxanthellae), but corals also harbour highly diverse, abundant, and stable, microbial communities. The discovery of bacterial communities as symbiotic partners in corals is surprisingly recent and the ecological function of these bacterial communities is still poorly understood.
Elucidating the functional role these mutualistic bacterial communities play in the corals’ multi-partner symbiosis (i.e. the holobiont) is essential to understand their importance in coral health. One important proposed functional role for coral associated bacteria is nitrogen fixation. Nitrogen ﬁxation can only be accomplished by diazotrophic bacteria and is fundamentally important because it makes gaseous dinitrogen (N2) available for nitrogen limited ecosystems such as coral reefs.
In this study, we investigated the diversity of diazotrophic bacterial communities associated with corals of the Great Barrier Reef (GBR) by profiling the conserved subunit of the nifH gene, which encodes the dinitrogenase iron protein. We looked at the diversity of diazotrophs in different: coral species, coral microhabitats (mucus and tissue), life stages and geographical regions. Coral mucus nifH sequences displayed high heterogeneity, and many bacterial groups overlapped with those found in seawater.
In contrast, the dominant diazotrophic bacteria in tissue samples in all coral species, through all life stages and at different locations were closely related to the bacterial group rhizobia, which represented over 67% of the total sequences in all cases. Our results suggest that, as in terrestrial plants, rhizobia have developed a mutualistic relationship with corals and may contribute fixed nitrogen to Symbiodinium.
Kim was born and grew up in Mexico City. She completed her BSc in Marine Science at the Centre d’Océanologie de Marseille, Université Aix-Marseille II (Marseille, France), with a thesis on a mathematical model for marine protected areas.
Stayed in France for some months after completing her BSc and worked with deep-sea bioluminescent bacteria at the LMGEM Marine microbiology and biogeochemistry laboratory, CNRS (National Centre of Scientific Research). Then, returned to Mexico, Yucatan Peninsula, and worked on migration models of marine turtles and whale sharks at the CINVESTAV (Centre of Advanced Research, Mexico) and PRONATURA(NGO).
Finally, felt ready to go further from home and flew to Australia. Completed a Master of Applied Sciences at James Cook University (Townsville, QLD) and went on to do a PhD. Kim is currently finalizing her PhD on “ Coral nitrogen Fixing bacteria” under the supervision of Prof. Bette Willis (JCU) and David Bourne (AIMS). One component of her thesis is through collaboration with Prof. Peta Clode at the CMCA (Centre of Microscopy) at UWA.
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