Cellular and environmental variables determining numbers of flagella in temperature-shocked Naegleria.

Naegleria gruberi amebae normally transform into biflagellated cells. When subjected to high temperatures during flagellate differentiation, populations develop an average of 4-5 flagella/flagellate. Attempts to maximize this phenomenon by altering cellular and environmental variables revealed that: (a) few Naegleria isolates become multiflagellated: strain NB-1 gives the greatest response to heat shocks; (b) temperature is the most critical variable: highest numbers of flagella are obtained only if cells are temperature-shocked at precisely 38.2 +/- 0.1 C, then returned to 19-22 C to complete differentiation; (c) although pH alone does not affect numbers of flagella, a pH optimum of 5.5-7.0 exists for temperature-shocked cells; and (d) single cells in microdrops become multiflagellated, but the population response is density-dependent. Optimal conditions are described for growing, washing, and transforming amebae to generate reproducibly highest numbers of flagella.