Radioprotective role of cyanobacterial phycobilisomes

Abstract

not peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was . http://dx.doi.org/10.1101/281386 doi: bioRxiv preprint first posted online Mar. 13, 2018; Cyanobacteria survived the Foton-M4 space mission 2 It is now generally accepted that cyanobacteria are responsible for production of oxygen, which led to the so-called "Great Oxygenation Event". Appearance of dioxygen in Earth's atmosphere resulted in formation of the ozone layer and the ionosphere, which caused significant reduction of ionizing radiation levels at the surface of our planet. This event not only increased biological diversity but also canceled the urgency of previously developed mechanisms of DNA protection, which allowed to survive and develop in harsh environmental conditions including exposure to cosmic rays. In order to test the hypothesis if one of the oldest organisms on Earth retained ancient protection mechanisms, we studied the effect of ionizing radiation (IoR, here: α-particles with a kinetic energy of about 30 MeV) and space flight during the mission of the Foton-M4 satellite on cells of Synechocystis sp. PCC6803. By analyzing spectral and functional characteristics of photosynthetic membranes we revealed numerous similarities between cells exposed to IoR and after the space mission. In both cases, we found that excitation energy transfer from phycobilisomes to photosystems was interrupted and the concentration of phycobiliproteins was significantly reduced. Although photosynthetic activity was severely suppressed, the effect was reversible and the cells were able to rapidly recover from stress under normal conditions.Moreover, in vitro experiments demonstrated that the effect of IoR on isolated phycobilisomes was completely different from such in vivo. These observations suggest that the actual existence and the uncoupling of phycobilisomes under irradiation stress could play specific role not only in photo-, but also in radioprotection, which was crucial for early stages of evolution and the development of Life on Earth.

Non-random genetic alterations in the cyanobacterium Nostoc sp. exposed to space conditions

“…However, individual compartments on the ISS facility experienced widely different UV fluences 7 due to complex shading and positions of the ISS in relation to the sun, which could not be reproduced individually for the ground experiment. Phycobilisomes, the light-harvesting antennas in cyanobacteria, play a significant role in photo- and radiation protection 35 . Specifically, cyanobacteria are capable of uncoupling phycobilisomes from photosynthetic membranes which could be a first step in preventing radiation damage and overexcitation of the photosystems.…”

Reactive Adsorption of Sulfur Compounds on Transition Metal Polycation‐Exchanged Zeolites for Desulfurization of Hydrocarbon Streams

“…Thea nalysis of the XAFS spectra was performed with the software VIPER for Windows. [46] Ther equired scattering amplitudes and phase shifts were calculated by the ab initio FEFF8.10 code [47] for CuO and ZnO.N ol ess than duplicate spectra were recorded to ensure data reproducibility.…”

The study of the biological effects of ionizing radiation on photosynthetic apparatus of cyanobacteria

“…PCC6803 характерны ФБС полудисковидной формы, основными фикобилипротеиновыми компонентами которой служат Сфикоцианин и аллофикоцианин. Энергия квантов, поглощенных фикобилинами, передается на хлорофилл РЦ ФС1 и ФС2, что позволяет увеличить эффективность фотосинтеза за счет использования света в спектральной области, где поглощение хлорофилла неэффективно [1].…”