Probing an Unusual Nitrogen Fixing Symbiosis

Symbiotic relationships between unicellular microorganisms are essential components of global ecosystems. Recently, a unique marine symbiosis was discovered between a microalga and an uncultivated unicellular cyanobacterium called UCYN-A. Analyses of UCYN-A revealed extensive genome reduction in this organism, but the retention of an elaborate nitrogen-fixing cluster. UCYN-A lacks the genes for oxygen-evolving photosystem II and carbon fixation, while the microalga has the ability to photosynthetically fix carbon. Studies revealed that a mutual exchange of carbon and nitrogen form the basis of this symbiotic relationship. We are unravelling this critical and fascinating evolutionary aspect of nature. Our objective is to identify the mechanisms (physical, chemical, and biological) that facilitate interactions leading to symbiosis between these two microorganisms. This study will use novel strategies including a state of the art fluorescence kinetic microscope (FKM) developed by Photon Systems Instruments (Czech Republic) for imaging photosynthetic activity in single cells. This work is funded by the Gordon and Betty Moore Foundation.

$1 million grant awarded to I-CARES Director and UCSC Professor