The production of asparaginase in standing
cultures depended upon protein synthesis. Cells
were first grown aerobically. The addition of
chloramphenicol at the time when the aeration
was discontinued prevented the appearance of
the enzyme. Dependence of enzyme formation
on protein synthesis indicated that its appearance
resulted from de novo synthesis rather than from
the conversion of a preexisting but inactive
protein precursor.
Roberts et al. (23) recently reported that, when
E. coli is grown for 12 to 16 hr with shaking,
there is a greater yield of asparaginase in air
than in an atmosphere of nitrogen. It was concluded
that anaerobiosis depressed the formation
of asparaginase II. The supply of oxygen is likely
to be limiting to cultures at high cell densities even when shaken in air. Thus, as these workers
have also shown (23), under their conditions of
cultivation, the highest concentration of asparaginase
appeared in cells as the bacteria
approached the end of growth.
Formation of asparaginase IH during anaerobic
growth. The experiments with standing cultures
suggested that asparaginase II might be produced
continuously and at high rates by bacteria adapted
to anaerobic conditions of growth. Bacteria
produced asparaginase II at a constant rate for
many generations during growth in anaerobic
jars. Under these conditions, formation of the
enzyme was stimulated greatly by the enrichment
of the mineral-salts-glucose medium with
tryptone, yeast extract, or casein hydrolysate