Nathan Ahlgren

Graduate Student 2001-2008

Presently: Postdoctoral Researcher  Dept. of Microbiology, UW

B.S. Biology. Massachusetts Institute of Technology. Cambridge, MA (1999)

M.S. Biological Oceanography. University of Washington. Seattle, WA (2003)

Ph.D. Biological Oceanography. University of Washington. Seattle, WA (2008)

Research interests: Ecology and evolution of marine Synechococcus

Marine Synechococcus provide an excellent model to explore the mechanisms of differentiation in marine bacteria. This abundant group of cyanobacteria is found throughout the world’s oceans, in both oligotrophic and coastal regimes and ranging from tropical to polar regions. Their ability to inhabit a wide range of habitats is attributed to the fact that this genus is comprised of several (at least 16) ecotypes–separate populations which which are genetically and physiologically distinct from each other. I am interested in understanding what physiological differences make these ecotypes distinct and the mechanisms that generate and maintain their coexistence.

More specific research interests:

  • the importance of light physiology and nitrogen utilization in differentiation of marine Synechococcus ecotypes
  • the role of periodic selective sweeps in the differentiation of marine Synechococcus ecotypes
  • the distribution of ecotypes in various environments (with depth through the water column and across oligotrophic and coastal regimes)


Ahlgren, N. A. and G. Rocap. 2006. Culture isolation and culture-independent clone libraries reveal new marine Synechococcus ecotypes with distinctive light and N physiologies. Applied and Environmental Microbiology 72: 7193-7204. PDF file (752 kb)

Ahlgren, N. A., G. Rocap, and S. W. Chisholm. 2005. Measurement of Prochlorococcus ecotypes using real-time polymerase chain reaction reveals different abundances of genotypes with similar light physiologies Environmental Microbiology 8: 441-454 PDF file (257 kb)

Rocap, G., F. W. Larimer, J. Lamerdin, S. Malfatti, P. Chain, N. A. Ahlgren, A. Arellano, M. Coleman, L. Hauser, W. R. Hess, Z. I. Johnson, M. Land, D. Lindell, A. F. Post, W. Regala, M. Shah, S. L. Shaw, C. Steglich, M. B. Sullivan, C. S. Ting, A. Tolonen, E. A. Webb, E. R. Zinser and S. W. Chisholm. 2003. Genome divergence in two Prochlorococcus ecotypes reflects oceanic niche differentiation. Nature 424: 1042-1047. PDF file (430 kb) 
Supplementary Information (418 kb)Mann, E. L., N. Ahlgren , Moffett, J. W., Chisholm, S. W. (2002) Copper toxicity and cyanobacteria ecology in the Sargasso Sea. Limnology and Oceanography 47(4): 976-988.