Tolerance of the Photosynthetic Apparatus to Acidification of the Growth Medium as a Possible Determinant of CO₂-Tolerance of the Symbiotic Microalga Desmodesmus sp. IPPAS-2014

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V. V. Ptushenko^1,2 and A. E. Solovchenko^3,4*

¹Lomonosov Moscow State University, Belozersky Research Institute of Physico-Chemical Biology, 119991 Moscow, Russia; E-mail: ptush@belozersky.msu.ru

²Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia

³Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia; E-mail: solovchenko@mail.bio.msu.ru

⁴Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia

^* To whom correspondence should be addressed.

Received June 7, 2016; Revision received July 21, 2016

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The symbiotic unicellular chlorophyte Desmodesmus sp. IPPAS-2014 capable of growth at extremely high CO₂ levels prohibitive for most other microalgae is an interesting model for studies of CO₂ tolerance mechanisms and a promising organism for CO₂ biocapture. We studied the initial (0-60 min) phase of acclimation of this microalga to an abrupt decrease in pH of the medium sparged with air/20% CO₂ mixture. Acclimation of the culture to these conditions was accompanied by a sharp decrease in photochemical activity of the chloroplast followed by its recovery with a characteristic time of 10-50 min. We hypothesize that acidification of the cultivation medium by dissolving CO₂ plays a key role in the observed decrease in the photochemical activity. The possible role of photosynthetic apparatus tolerance to abrupt acidification in overall high tolerance of symbiotic microalgae to extremely high CO₂ levels is discussed.

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KEY WORDS: acidification, chlorophyll fluorescence, stress, tolerance

DOI: 10.1134/S0006297916120142

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