Diversity of the ribosomal structures in the Euglena gracilis chloroplast genome: description of a mutant with two ribosomal operons and possible mechanism for its production.

We studied the bleached mutant of Euglena gracilis Y3BUD producing carotenoids and rich in chloroplast DNA. This mutant which was produced more than twenty years ago segregates permanently, forming 30 to 50% daughter cells without carotenoids and poor in chloroplast DNA. Electron microscopy and mapping with restriction enzymes show the deletion of a complete ribosomal operon out of the three present in the original strain.