Figure 1.
Algicaidal effect of RPS supernatant on P. globosa at different time points.
Data points: mean ± standard deviation of triplicate assays. Error bars not visible are smaller than symbols. The algal biomass treated with RPS supernatant decreased dramatically in 48 h. A significant interactive effect of RPS supernatant and time was also observed by analysis of two-way ANOVA (P<0.001).
Figure 2.
Morphology (A) and phylogenic tree (B) of RPS.
Morphology from SEM results (JSM-6390, JEOL) and phylogenic tree based on 16S rDNA sequences by Neighbor-Joining analysis. Kitasatospora setae KM-6054 (NR_037063) was used as the out group.
Table 1.
Culture characteristics of RPS at 28°C on different media.
Figure 3.
Algicide release mode of RPS against P. globosa.
Data from RFU assay of algicidal effect (1∶10, v:v). Data points: mean ± standard deviation of triplicate assays. Treatment means with different letters differed significantly (P<0.001), analyzed using one-way ANOVA.
Figure 4.
Sensitivity of supernatant algicidal activity to temperature (A) and pH (B).
Data from RFU assay of algicidal effect (1∶10, v:v). Control represents the initial fermentation broth without any treatments. Data points: mean ± standard deviation of triplicate assays. Temperature treatment means with different letters in (A) differed significantly (P<0.001) by analysis of one-way ANOVA, suggesting that the algicidal activity of RPS is sensitive to temperature, while no significant difference (P>0.05) was observed among treatments with pH in (B), meaning that the activity is insensitive to pH.
Figure 5.
Algicidal activity of initial supernatant and dialyzed supernatants (A) and different organic solvent extracts (B).
Data from RFU assay. Data points: mean ± standard deviation of triplicate assays. In (A), initial supernatant (Control) and dialyzed supernatants were added at 10% ratio, and treatment means with different letters differed significantly (P<0.001) by analysis of one-way ANOVA. In (B), 10 μL extract was added into 1.99 mL algal culture (equal to 1∶10 of v:v in algicidal substance dose, no loss considered during extraction), and treatment means with different letters differed significantly (P<0.05) by analysis of one-way ANOVA.
Figure 6.
Morphological changes of P. globosa treated by ethyl acetate extract from RPS supernatant within 48 h.
(A) normal P. globosa, (B) flagella falling off the alga, (C) broken cells, and (D) algae at different damaged levels. The putative algicidal process is that the algicidal substance inhibits the movement of P. globosa, then causes the flagella to fall off the algae, and finally lyses the algal cells.
Table 2.
Susceptibility of algae to ethyl acetate extract of RPS supernatant.