FIG. 3.

Effect(s) of fish-derived factor(s) on proliferation of P. piscicida dinospores in vitro. (A) Survival of P. piscicida dinospores without prey algae. The stationary-phase P. piscicida culture was maintained without additional prey and fresh medium for an extended 21 days with the supplement of ASW (striped bars), SAW (dotted bars), or F-SAW filtered through a 0.2-μm-pore-size membrane (white bars). Dinospore cell densities were counted on days 0, 7, 14, and 21 after the supplemental inoculation (n, 4 replicates). (B and C) Proliferation of P. piscicida dinospores with and without fish-derived factor(s). SAW or ASW (250 ml) was mixed with the culture (250 ml) of P. piscicida on Rhodomonas (at final densities of 1.0 × 10³ P. piscicida cells and 1.9 × 10⁴ Rhodomonas cells ml⁻¹) and the culture was maintained under the standard conditions (error bars, standard deviations; n, 3 replicate experiments). Cell densities of P. piscicida (○ and •) and prey Rhodomonas (□ and▪) were counted. Symbols correspond to fish-derived factor(s) (○ and □) and ASW (• and ▪). Panel B is focused on the growth rates of P. piscicida during the exponential phase from panel C.