The ultrastructure of the outer cell wall-layer ofChlorella mutants with and without sporopollenin

Chlorella fusca wild type strain C-1.1.10 is able to synthesize ketocarotenoids (KC) and sporopollenin (SP) which are present in the cell wall (CW) as integral components. Mutants derived from this strain are unable to synthesize KC and SP. The CW ultrastructure of both, wild type and mutants, was investigated by TEM after different staining procedures. Strains containing SP in the CW exhibit a trilaminar structure of the outer layer of the CW, while mutants defective in KC- and SP-synthesis differ in this respect. Fragments of unit membranes, various membranous vesicles and structures often are found in the space between the CW and the plasmalemma; this perhaps indicates some steps of CW- and sporopollenin-synthesis. These findings again strongly confirm the close connection between the synthesis of KC, SP, and the trilaminar structure of the outer CW-layer.