FIG. 4.

Encystment and excystment of P. piscicida cells in vitro. (A) Encystment of P. piscicida in vitro. The stationary-phase P. piscicida dinospore culture was placed at 4°C in darkness for 28 days. Cells in the water column were counted during encystment (n = 3 replicates). The inset is a SEM image of P. piscicida cysts yielded by in vitro culture under these conditions. (B) Excystment of P. piscicida in vitro. A culture of encysted P. piscicida cells was incubated at 23°C under a standard light cycle for monitoring the emergence of dinospores from cysts (error bars, standard deviations; n, 3 replicate experiments). Densities of dinospores emerging between sampling time points are shown in the inset.