活動備忘 Event Memo：
The unicellular eukaryotic red algae of Cyanidiophyceae, including Cyanidioschyzon, Cyanidium
and Galdieria, are of special interest due to
their habitats and systematic position. Most of the cyanidiophytes occupy acidic habitats (pH 0-4),
which are detrimental to almost all other eukaryotes, and can survive up to
56°C, close to the upper temperature limit for eukaryotic life. Molecular
phylogenetic data suggest that this enigmatic algal group diverged very early
in the evolution of Rhodophyta. Within the Cyanidiophyceae, Galdieria
has drawn much attention as it is able to grow heterotrophically on more than 50 carbon sources.
The ecological significance of this metabolic versatility, however, is not
clear. In attempt to address this question, G. partita
isolated in the Tatun Volcano Group area, Taiwan, was axenically cultured under different growth
conditions. Here we showed that G. partita
cells stopped growing and were damaged under continuous high light (300 µmol
photons m-2 s-1).
When culture media were supplemented with 25 mM of glucose, the growth of G.
partita was recovered in high light.
Further analyses suggest that carotenoids are crucial in protecting G.
partita from cell damage in high light,
most likely through scavenging reactive oxygen species generated by light. The
high-light sensitivity of G. partita
cells is in accordance with the distribution of their communities limited to epilithic and endolithic microhabitats.
Furthermore, we hypothesize that G. partita
may acquire or retain its capability to uptake various exogenous organic
carbons to enhance its tolerance to high light.