title: Genome divergence in two Prochlorococcus ecotypes reflects oceanic niche differentiation.
abstract: The marine unicellular cyanobacterium Prochlorococcus is the smallest-known oxygen-evolving autotroph. It numerically dominates the phytoplankton in the tropical and subtropical oceans, and is responsible for a significant fraction of global photosynthesis. Here we compare the genomes of two Prochlorococcus strains that span the largest evolutionary distance within the Prochlorococcus lineage and that have different minimum, maximum and optimal light intensities for growth. The high-light-adapted ecotype has the smallest genome (1,657,990 base pairs, 1,716 genes) of any known oxygenic phototroph, whereas the genome of its low-light-adapted counterpart is significantly larger, at 2,410,873 base pairs (2,275 genes). The comparative architectures of these two strains reveal dynamic genomes that are constantly changing in response to myriad selection pressures. Although the two strains have 1,350 genes in common, a significant number are not shared, and these have been differentially retained from the common ancestor, or acquired through duplication or lateral transfer. Some of these genes have obvious roles in determining the relative fitness of the ecotypes in response to key environmental variables, and hence in regulating their distribution and abundance in the oceans.
authors.affiliation: School of Oceanography, University Of Washington, Seattle, Washington 98195, USA.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Rocap
authors.forename: Frank W
authors.initials: FW
authors.lastname: Larimer
authors.forename: Jane
authors.initials: J
authors.lastname: Lamerdin
authors.forename: Stephanie
authors.initials: S
authors.lastname: Malfatti
authors.forename: Patrick
authors.initials: P
authors.lastname: Chain
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ahlgren
authors.forename: Andrae
authors.initials: A
authors.lastname: Arellano
authors.forename: Maureen
authors.initials: M
authors.lastname: Coleman
authors.forename: Loren
authors.initials: L
authors.lastname: Hauser
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Hess
authors.forename: Zackary I
authors.initials: ZI
authors.lastname: Johnson
authors.forename: Miriam
authors.initials: M
authors.lastname: Land
authors.forename: Debbie
authors.initials: D
authors.lastname: Lindell
authors.forename: Anton F
authors.initials: AF
authors.lastname: Post
authors.forename: Warren
authors.initials: W
authors.lastname: Regala
authors.forename: Manesh
authors.initials: M
authors.lastname: Shah
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Shaw
authors.forename: Claudia
authors.initials: C
authors.lastname: Steglich
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Sullivan
authors.forename: Claire S
authors.initials: CS
authors.lastname: Ting
authors.forename: Andrew
authors.initials: A
authors.lastname: Tolonen
authors.forename: Eric A
authors.initials: EA
authors.lastname: Webb
authors.forename: Erik R
authors.initials: ER
authors.lastname: Zinser
authors.forename: Sallie W
authors.initials: SW
authors.lastname: Chisholm
mesh_terms: D000222:Adaptation, Physiological / Q000528:radiation effects; D005075:Biological Evolution; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics* / Q000528:radiation effects; D004777:Environment; D005798:Genes, Bacterial / Q000235:genetics; D016680:Genome, Bacterial; D008027:Light; D008969:Molecular Sequence Data; D009792:Oceans and Seas; D010802:Phylogeny