Discovery of Symbiotic Nitrogen-Fixing Cyanobacteria in Corals
Michael P. Lesser,1*
Charles H. Mazel,2
Maxim Y. Gorbunov,3
Paul G. Falkowski3,4
Colonies of the Caribbean coral Montastraea cavernosa exhibit a solar-stimulated orange-red fluorescence that is spectrally similar to a variety of fluorescent proteins expressed by corals. The source of this fluorescence is phycoerythrin in unicellular, nonheterocystis, symbiotic cyanobacteria within the host cells of the coral. The cyanobacteria coexist with the symbiotic dinoflagellates (zooxanthellae) of the coral and express the nitrogen-fixing enzyme nitrogenase. The presence of this prokaryotic symbiont in a nitrogen-limited zooxanthellate coral suggests that nitrogen fixation may be an important source of this limiting element for the symbiotic association.
1 Department of Zoology and Center for Marine Biology, University of New Hampshire, Durham, NH 03824, USA.
2 Physical Sciences, 20 New England Business Center, Andover, MA 01810, USA.
3 Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA.
4 Department of Geological Sciences, Rutgers University, Piscataway, NJ, USA.
* To whom correspondence should be addressed. E-mail: mpl{at}cisunix.unh.edu
