Photophysiology of Bolidomonas pacifica

Bolidomonas pacifica is a member of the Bolidophytes, chlorophyll a/c phytoplankters that lack siliceous frustules, in contrast to their sister lineage the diatoms. Under nutrient repletion, B. pacifica achieved a maximum growth rate of ∼0.51 day ―1 at a growth light of 224 μmol photons m ―2 s ―1 , with a light compensation point for growth slightly below 30 μmol photons m ―2 s ―1 The effective absorbance cross section for blue light for Photosystem II (PSII) for cells growing under low light was 1071 (± 64) A 2 quanta ―1 with a modest decrease in cells growing under higher lights. Upon upward shifts in light, B. pacifica induced PSII repair within 15 min to stabilize PSII function in the face of accelerated photoinactivation, and the cells then achieved significant light acclimation within 1 h. When PSII repair was blocked, the cells suffered progressive loss of PSII function with a target size for susceptibility to photoinactivation of 7 × 10 ― 5 (±0.5 x 10 ―5 ) A 2 quanta ―1 , across a range of growth lights. In comparison with similarly sized marine centric diatoms, B. pacifica shows larger absorbance cross sections serving PSII photochemistry but relies upon PSII repair to counter a higher intrinsic susceptibility to photoinactivation.