Phycobilisome ultrastructure and chromatic adaptation in Fremyella diplosiphon

Abstract

Phycobilisomes isolated from the cyanobacterium Fremyella diplosiphon were negatively stained with uranyl sulphate and examined by transmission and scanning transmission electron microscopy. They were composed of a central triangular core of discs and six peripheral stacks of discs radiating out from the core. The peripheral stack discs were identified as phycobiliprotein hexamers on the basis of their size and morphology. Phycobilisomes from cells grown under white light were compared with phycobilisomes from cells grown under red light. The two types of phycobilisomes differed widely in their phycobiliprotein composition, but were closely similar in structure, varying only in the number of peripheral stack discs. The structure described here for F. diplosiphon phycobilisomes is consistent with a recently proposed model for cyanobacterial phycobilisomes. © 1981 Annals of Botany Company.