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UCYN-A1 (Red) & A1 host (green and blue)

Zehr (2015) 

UCYN-A2 (Red) & A2 host (green and blue)

Zehr (2015) 

CARD-FISH images by M. Munoz-Marin

Diversity, distribution, genomics and activity of prymnesiophyte-UCYN-A associations 


The unicellular cyanobacteria group A (UCYN-A), was originally detected by amplification of nifH gene fragments from the oligotrophic ocean using the polymerase chain reaction (PCR), and research in our lab has reveled that it has extensive genome reduction and lives in symbiosis with a small unicellular eukaryotic alga in the Prymnesiophyceae (haptophyte) group.  This association between a bacterium containing a reduced phototrophic genome and a unicellular eukaryote is reminiscent of the evolution of the chloroplast. 


We have recently discovered higher than expected genetic diversity among this cyanobacterial symbiont. The genome of a second strain, UCYN-A2 lacks the same critical genes, yet has diverged substantially in DNA sequence (80-90%). UCYN-A2 also lives in association with a different B. bigelowii strain.


This symbiosis presents intriguing questions regarding microbial interactions, evolution and symbiosis. Our curent research focuses on understanding how the genomes of the B. bigelowii hosts compare to other non-symbiont containing alga, whether and how the growth of the symbiont and host are coordinated, the nature of their physical association, whether there is yet undiscovered diversity of these organisms, and gene expression in the symbiont in response to changes in resources and activity of the host. 

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