Fig. 2.

Growth phenotype of Δspdsyn promastigotes. Wild-type, Δspdsyn1, and Δspdsyn1(pXG-BSD-SPDSYN) [Δspdsyn1(pSPDSYN)] promastigotes were incubated in their respective growth media in the absence or presence of 100 μM spermidine or 100 μM putrescine. Δspdsyn1 parasites were starved of exogenous polyamines 2 days prior to the start of the growth assay. Parasites were inoculated at 5 × 10⁴ cells/ml, maintained at 26°C with 5% CO₂, and enumerated after 4 days. Reported cell densities represent final cell densities minus inoculation densities. Final cell densities of Δspdsyn1 parasites grown under nonpermissive conditions were significantly lower than those of the initial inocula, and thus, growth was zero.