Prochlorococcus marinus str. MIT 9515

Prochlorococcus, a fairly recently discovered cyanobacterium (1988), is the smallest known free-living photosynthetic prokaryote. Despite its small size it contributes significantly to global nutrient cycling. It is unique among cyanobacteria in using divinyl chlorophyll a and b as the major light-harvesting pigments, and harvests light with chlorophyll-binding antenna proteins (Pcb proteins) instead of the phycobilisomes used by most cyanobacteria. It is found in low- to mid-latitude oceans and seas, thriving in nutrient-poor waters and at greater depths than its close relative Synechococcus (down to 135m for Prochlorococcus, but only 95m for Synechococcus). Prochlorococcus can be differentiated into low-light (LL) and high-light (HL)-adapted ecotypes that have different physiologies and exist at different depths. Comparison of 12 whole genomes suggests the core genome contains about 1250 genes, while the pan-genome will have more than 5800 genes.This LL-adapted strain was isolated from the North Atlantic Ocean at 10m depth in April 1990. Its chlorophyll b/a ratio is 0.97 and it belongs to high chlorophyll b/a clade I. (HAMAP: PROMT)