The effect of mercaptoethanol on flagellar morphogenesis in the amoeboflagellate Naegleria gruberi (Schardinger)

β-Mercaptoethanol added to cultures of Naegleria gruberi at any time after the induction of flagellation by washing, leveled the flagellation curve at a time 20 min later than the time of addition of the drug. When the mercaptoethanol was removed from blocked amoebae, there was subsequent recovery. Treatment with mercaptoethanol for 20-60 min caused excess delay in recovery such that the cells were setback to the time of induction (t₀). Comparison of the time of sensitivity to mercaptoethanol vs. actinomycin D indicated that the primary effect of mercaptoethanol occurs at a later point in flagella morphogenesis than RNA synthesis. Sensitivity to actinomycin D characteristic of newly induced amoebae was not restored to such cells setback to t₀ provided only a short time (< 120 min) had elapsed since induction. These results are interpreted in terms of mercaptoethanol's hypothesized effect on the assembly of precursor protein molecules into ordered structures and suggest that manufacture or polymerization of certain microtubular or fibrous elements begins almost immediately upon induction of flagellation.