Diatoms are found in marine environments worldwide and are responsible for 20% of global primary production. We conducted experiments on the diatom Phaeodactylum tricornutum ecotype Pt1, collected off the coast of Blackpool, England. Under typical growth conditions diatoms fluoresce at 680 nm; however, previous research has shown that when P. tricornutum is grown under light stress, a fluorescence peak at 710 nm is induced, known as the F710 state. Our experiments investigate whether F710 emission is a generalized stress response, and how F710 fits into the overall light-harvesting energy transfer scheme in P. tricornutum. We cultured Pt1 under a range of iron conditions (0.1-11.7 μM Fe³⁺) and conducted steady-state and time-resolved fluorescence experiments to observe the effects of iron stress on F710 emission. We observe fluorescence emission from the F710 state under iron stress, indicating that F710 is not a specifically red-light stress response (Figure 1). Fluorescence lifetime experiments provide insight into the energy transfer dynamics. At lower iron concentrations, our data reveal energy transfer from 680 nm into the F710 state. Studying diatom light harvesting under lower iron concentrations could further expand our understanding of how diatoms adapt to external stressors.

Figure 1: Normalized steady-state emission spectrum following 403 nm excitation of <i>Phaeodactylum tricornutum</i> ecotype Pt1 cells grown under varying iron concentrations. Fluorescence emission at 710 nm increases when cells are grown under low iron (0.1 μM and 1.0 μM) concentrations.

Figure 1: Normalized steady-state emission spectrum following 403 nm excitation of Phaeodactylum tricornutum ecotype Pt1 cells grown under varying iron concentrations. Fluorescence emission at 710 nm increases when cells are grown under low iron (0.1 μM and 1.0 μM) concentrations.

Noor Nazeer

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