Why Sequence Prochlorococcus?

The overall goal of this project is to understand the genomic underpinnings of the observed ecological diversity and distribution of Prochlorococcus. This unicellular cyanobacterium is an extremely abundant primary producer in the world’s oceans, is the smallest known oxygenic phototroph, and has a compact genome (as small as 1.7 Mbp). Its abundance and phototrophic metabolism make Prochlorococcus an important link in global carbon cycling through CO₂ fixation. Involving Prochlorococcus cells from the surface and from deeper in the euphotic zone (at depths of 30 m and 120 m), the research will focus on estimation of the total genomic diversity of Prochlorococcus, the nature of variation among genomes, and comparison of environmental sequences with those of cultured strains. The comparison of genomic diversity between bacteria in the field and in previously sequenced cultured isolates will allow us to establish testable hypotheses of genotype-phenotype connection and niche differentiation. The sequencing project is part of a long-term investigation to determine the connection between genomic variation, phenotypic properties, and ecological distribution in Prochlorococcus.

CSP project participants: Sallie W. Chisholm (proposer) and Martin Polz (Massachusetts Inst. of Technology).