A new prokaryote containing chlorophylls a and b

Abstract

Prochlorophyta, suggested as a new division of prokaryotes1, lack phycobilin pigments characteristic of cyanobacteria, but contain chlorophyll b as well as chlorophyll a, characteristic of green algae and higher plants. Since the description of Prochloron didemni as the type species for this division2, no other genera or species have been added to the group. The only published accounts of Prochloron are obligate symbionts of didemnid ascidians3, which are difficult to grow in the absence of their hosts4. Consequently, research on their cell composition and physiology has been handi-capped. Here, we report a second prochlorophyte. This organism is one of the dominant species in the shallow eutrophic Loosdrecht lakes in The Netherlands, from which it was isolated in 1984. Unlike Prochloron, the newly isolated species is filamentous and planktonic. Detailed investigation of its cell structure, composition and physiology is possible as it can easily be grown in a mineral medium.