Genomic Islands and the Ecology and Evolution of Prochlorococcus

Coleman, Maureen L.
Sullivan, Matthew B.
Martiny, Adam C.
Steglich, Claudia
Barry, Kerrie
DeLong, Edward F.
Chisholm, Sallie W.

¹Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 15 Vassar Street, Cambridge, MA 02139, USA. ²U.S. Department of Energy Joint Genome Institute, Production Genomics Facility, Walnut Creek, CA 94598, USA.

*Present address: University Freiburg, Department of Biology II/Experimental Bioinformatics, Schänzlestrasse 1, D-79104 Freiburg, Germany.

†To whom correspondence should be addressed. E-mail: [email protected]

Supporting Online Material: www.sciencemag.org/cgi/content/full/311/5768/1768/DC1; Materials and Methods; Figs. S1 to S5; Tables S1 to S3; References

31 October 2005; accepted 17 February 2006

10.1126/science.1122050

Science 311(5768):p 1768-1770, March 24, 2006.

Prochlorococcus ecotypes are a useful system for exploring the origin and function of diversity among closely related microbes. The genetic variability between phenotypically distinct strains that differ by less that 1% in 16S ribosomal RNA sequences occurs mostly in genomic islands. Island genes appear to have been acquired in part by phage-mediated lateral gene transfer, and some are differentially expressed under light and nutrient stress. Furthermore, genome fragments directly recovered from ocean ecosystems indicate that these islands are variable among co-occurring Prochlorococcus cells. Genomic islands in this free-living photoautotroph share features with pathogenicity islands of parasitic bacteria, suggesting a general mechanism for niche differentiation in microbial species.