Table 3.
Effect of nitrate depletion in Aphanizomenon gracile UAM529 grown at 23 °C in two different culture media (BG11, with nitrate, and BG110, without nitrate). Data show mean ± standard deviation of three replicates (n = 3). Asterisks indicate significant differences of BG110—grown culture compared to BG11 (p < 0.05, t-test). Expression data of BG110 are relative to BG11 expression, which was set to 1 to facilitate comparison.
| Culture Medium | Ecophysiology | Toxin Production/Release | Relative Expression | ||||
|---|---|---|---|---|---|---|---|
| Growth Rate (day−1) | Chl a Content (mg g−1 DW) |
Total STX Content (µg mg−1 DW) |
Extracellular STX (%) | sxtA | sxtM | sxtPer | |
| BG11 | 0.17 ± 0.03 | 13.6 ± 2.4 | 0.20 ± 0.08 | 11.8 ± 6.1 | 1.0 ± 0.01 | 1.0 ± 0.02 | 1.0 ± 0.01 |
| BG110 | 0.05 ± 0.01 * | 7.6 ± 1.9 * | 0.15 ± 0.04 | 51.2 ± 20.2 * | 1.5 ± 0.5 | 1.2 ± 0.5 | 1.1 ± 0.3 |
Chl a = chlorophyll a; DW = dry weight: STX = saxitoxin.