Genomic taxonomy of the genus prochlorococcus

Area of Science:

• Marine microbiology
• Oceanography
• Genomics

Background:

• Prochlorococcus is a globally abundant marine cyanobacterium, dominating phytoplankton biomass in oligotrophic oceans.
• The genus Prochlorococcus, previously considered a single species (Prochlorococcus marinus) with six ecotypes, required taxonomic clarification.

Purpose of the Study:

• To analyze the taxonomic structure of the genus Prochlorococcus using comprehensive genomic methods.
• To establish a refined taxonomic framework for Prochlorococcus species.

Main Methods:

• Analysis of 13 complete genomes of cultured Prochlorococcus strains using multilocus sequence analysis, amino acid identity, Karlin genomic signature, and genome-to-genome distance.
• Estimation of Prochlorococcus species diversity in over 100 marine metagenomes from major oceanic provinces.

Main Results:

• The 13 analyzed Prochlorococcus strains represent ten distinct species, not a single species.
• A new taxonomic framework for the genus Prochlorococcus has been established based on genomic data.
• Metagenomic analysis suggests a global diversity of approximately 35 Prochlorococcus species.

Conclusions:

• High selective pressures in the global ocean likely limit Prochlorococcus diversification.
• The revised taxonomy provides a more accurate understanding of Prochlorococcus diversity and ecological roles.