The cyanobacterium <i>Prochlorococcus</i> has divergent light-harvesting antennae and may have evolved in a low-oxygen ocean
Osvaldo Ulloa, Carlos Henríquez‐Castillo, Salvador Ramírez‐Flandes, Álvaro M. Plominsky, Alejandro A. Murillo, Connor Morgan‐Lang, Steven Hallam, Ramūnas Stepanauskas
Abstract
Significance The marine unicellular cyanobacterium Prochlorococcus is the most abundant photosynthetic organism on Earth. Members of this genus are classically thought to be adapted to high-oxygen and nutrient-poor ocean conditions, with a principle divergence between high-light and low-light ecotypes. We show that the most basal Prochlorococcus lineages are adapted to the low-oxygen, low-light, and high-nutrient conditions found in the dimly illuminated waters of anoxic marine zones. The most basal lineages have retained phycobilisomes as light-harvesting antennae—a characteristic of most other cyanobacteria—whose loss was thought to define all Prochlorococcus . As oxygenic photosynthesis drove ocean oxidation in the ancient Earth, oxygen appears to have played as much a role as light and nutrients in driving Prochlorococcus evolution.