Acclimation of Chlamydomonas reinhardtii to extremely strong light

Abstract

Most photosynthetic organisms are sensitive to very high light, although acclimation mechanisms enable them to deal with exposure to strong light up to a point. Here we show that cultures of wild-type Chlamydomonas reinhardtii strain cc124, when exposed to photosynthetic photon flux density 3000 μmol m−2 s−1 for a couple of days, are able to suddenly attain the ability to grow and thrive. We compared the phenotypes of control cells and cells acclimated to this extreme light (EL). The results suggest that genetic or epigenetic variation, developing during maintenance of the population in moderate light, contributes to the acclimation capability. EL acclimation was associated with a high carotenoid-to-chlorophyll ratio and slowed down PSII charge recombination reactions, probably by affecting the pre-exponential Arrhenius factor of the rate constant. In agreement with these findings, EL acclimated cells showed only one tenth of the 1O2 level of control cells. In spite of low 1O2 levels, the rate of the damaging reaction of PSII photoinhibition was similar in EL acclimated and control cells. Furthermore, EL acclimation was associated with slow PSII electron transfer to artificial quinone acceptors. The data show that ability to grow and thrive in extremely strong light is not restricted to photoinhibition-resistant organisms such as Chlorella ohadii or to high-light tolerant mutants, but a wild-type strain of a common model microalga has this ability as well.

The Effect of Chilling on the Photosynthetic Apparatus of Microalga Lobosphaera incisa IPPAS C-2047

“…The same trend was discovered for the Car/Chl ratio indicative of PSA acclimation to the excessive light [23,44,45]. The content of individual Cars meas ured by HPLC was also insensitive to the chilling: neither VAZ nor de epoxidized VAZ xanthophylls (reflected as the DE value) revealed statistically significant changes.…”

Influence of Light Conditions on Microalgae Growth and Content of Lipids, Carotenoids, and Fatty Acid Composition

“…Algae grown under various light intensities show changes in biomass formation rate, pigment and lipid content, fatty acid composition, and ratio. For this purpose, various researchers have studied a fairly wide range of light intensity: from 5 to 3500 µmol photons m −2 s −1 [31,43,47,53,[77][78][79][80].…”

“…Recent studies have shown that the strains Chlamydomonas reinhardtii cc124 and Chlorella ohadii, which are able to grow under very strong lighting-3000 and 3500 µmol photons m −2 s −1 , respectively, exhibit high resistance to photoinhibition [31,80]. The strain Chlorella ohadii was isolated from a biological sand crust from the Sinai Desert in the northwestern Negev, Israel [31], and Chlamydomonas reinhardtii cc124 is a laboratory strain widely used as a wild type.…”

Differences in susceptibility to photoinhibition do not determinegrowth rate under moderate light in batch or turbidostat - a studywith five green algae

“…The highest light intensity at which a phototroph (an alga in this case) gains energy (i.e., the highest intensity at which the costs of PSII repair do not exceed the energy that can be obtained by photosynthesis) depends on the species (Murphy et al 2017). In addition, acclimation allows for example the green alga Chlamydomonas reinhardtii to grow at the extreme PPFD of 3,000 μmol(photon) m -2 s -1 (Virtanen et al 2021). It is concluded that all the tested algal species were able to grow under the light intensity used in the present study [200 μmol(photon) m -2 s -1 ].…”