A class of prokaryotic organisms coextensive with the division Prochlorophycota in the kingdom Monera. Because prochlorophytes carry out oxygen-evolving photosynthesis, they may be considered algae. They are distinguished from Cyanophyceae, the only other prokaryotic algae, by the presence in their photosynthetic lamellae of chlorophyll b in addition to chlorophyll a and the absence of phycobilin pigments. Otherwise, they resemble Cyanophyceae biochemically and ultrastructurally. The class comprises a single genus, Prochloron, with one species.