Effect of iron on the growth of Phaeodactylum tricornutum via photosynthesis.

Iron is a limiting factor that controls the phytoplankton biomass in the modern ocean, and iron fertilization of the ocean could lead to blooms dominated by diatoms. Thus, iron plays an important role in controlling the distribution of diatoms. In this study, we measured the growth rate and photosynthetic activity of the model diatom Phaeodactylum tricornutum cultured under different iron concentrations and found that it grew more rapidly and had a much higher photosynthetic efficiency under higher iron concentrations. In order to explore the unique mechanism of the response of diatoms to iron, a proteomic analysis was carried out, and the results indicated that iron promotes the Calvin cycle of P.tricornutum. Diatoms can tolerate the pressure of iron limitation by replacing iron-rich proteins with flavodoxin, and so on. Moreover, we found that the photosystem I (PSI) activity of iron-limited algae that were treated by N',N',N',N'-tetramethyl-p-phenylenediamine (TMPD) was increased significantly. As TMPD plays the role of a cytochrome b(6)/f complex that transfers electrons from photosystem II to PSI, the cytochrome b(6)/f complex is the key to photosynthesis regulation. Iron could influence the growth of P.tricornutum by regulating its biosynthesis. All of the results suggest that iron might affect the growth of diatoms through the Calvin cycle and the cytochrome b(6)/f complex.