Types of cell-wall material. Various substrates,
rich in wall materials, were explored for use as
carbon sources in culture media. Autolyzed and
washed baker's yeast (AWY) was used in some
parts of this work. Equal amounts by weight of
water and commercial compressed baker's yeast
were mixed. A small amount of toluene was added
and the suspension was incubated at 55 C for 3
days. The insoluble residue was centrifuged, and
was washed with distilled water by repeated
centrifugations until the supernatant liquid was
free from cytoplasmic particles. The cell paste
was lyophilized and stored in a desiccator. AWY
cells (Fig. la) have distinct cell walls clearly
discernible with either a phase contrast or a light
microscope. The cytoplasmic contents are somewhat
retracted from the cell walls because of