Starvation of Prototheca zopfii

The colourless alga Prototheca zopfii survived carbon-starvation for at least 110 d. Over a period of 21 d total numbers of organisms and viable organisms declined by 62% and 68% respectively. Both acetate-supported and endogenous respiration rates decreased, and the values for adenylate charge decreased from 0·95 to 0·015 after 5 d starvation. Complex changes in respiratory enzymes, catalase and acid hydrolases occurred over a 27 d period; cytochromes b and c were modified to protohaem-like and haem c-like compounds, and no haem a derivative could be detected. Ultrastructural changes included indentation of cell walls, shrinkage of the cytoplasmic mass, and disorganization of mitochondrial inner membranes, although recognizable mitochondrial profiles were still present after 43 d.