Fig. 3
Functional assays showed that the carbolines impact the growth, morphology, and infection rate of the marine diatom C. granii. a β-Carboline and 4-CTC inhibit the growth of C. granii algal cells at 6 and 24 µM, respectively (mean growth rates ± SE, one-way ANOVA with multiple comparisons against the DMSO group, Holm–Sidak method, F = 26, dF = 8, n = 3, *** for p value >0.001). b The infection rate was elevated in cultures treated with 4-CTC (>6 µM) after 3 and 5 days of incubation. Statistical tests, a two-way repeated measures ANOVA with pairwise multiple comparison (F = 17, dF = 8, n = 27) and the Dunnett’s method with multiple comparisons against the DMSO group found significant differences with the treatments highlighted by *** for p-value <0.001, ** for p value <0.01, * for p value <0.05. Mean of the infection rates was determined ±SE. c The phenotype of cells treated with β-carboline at 24 µM and 4-CTC (6 µM) (pictures on the right) was similar to the untreated infected cells (second picture from left). Plasmolysis was observed with vacuolization (white arrows) and some cytoplasmic detachment (blue arrow). Scale bars equal 20 µm, representative pictures of three replicates are shown
