Molecular investigation of the radiation resistance of edible cyanobacterium Arthrospira sp. PCC 8005

Abstract

The aim of this work was to characterize in detail the response of Arthrospira to ionizing radiation, to better understand its radiation resistance capacity. Live cells of Arthrospira sp. PCC 8005 were irradiated with 60Co gamma rays. This study is the first, showing that Arthrospira is highly tolerant to gamma rays, and can survive at least 6400 Gy (dose rate of 527 Gy h−1), which identified Arthrospira sp. PCC 8005 as a radiation resistant bacterium. Biochemical, including proteomic and transcriptomic, analysis after irradiation with 3200 or 5000 Gy showed a decline in photosystem II quantum yield, reduced carbon fixation, and reduced pigment, lipid, and secondary metabolite synthesis. Transcription of photo-sensing and signaling pathways, and thiol-based antioxidant systems was induced. Transcriptomics did show significant activation of ssDNA repair systems and mobile genetic elements (MGEs) at the RNA level. Surprisingly, the cells did not induce the classical antioxidant or DNA repair systems, such superoxide dismutase (SOD) enzyme and the RecA protein. Arthrospira cells lack the catalase gene and the LexA repressor. Irradiated Arthrospira cells did induce strongly a group of conserved proteins, of which the function in radiation resistance remains to be elucidated, but which are a promising novel routes to be explored. This study revealed the radiation resistance of Arthrospira, and the molecular systems involved, paving the way for its further and better exploitation.

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

“…Other cyanobacteria are even more radioresistant, almost as the champion bacterium Deinococcus radiodurans [100% survival at 5kGy (Moseley and Mattingly, 1971; Ito et al, 1983)]. These radiation-resistant cyanobacteria are Chroococcidiopsis [10% survival to 4–5 kGy of gamma rays (Billi et al, 2000)], three Anabaena strains [they can grow at 5 kGy (Singh et al, 2010)] and Arthrospira PCC8005 [it grows at 800 Gy (Badri et al, 2015)]. Thus, cyanobacteria might be used in the future for leaching (and/or sequestration) of radionuclides (Acharya and Apte, 2013).…”

“…In some cyanobacterial genomes uvrA, uvrB, uvrC , and/or uvrD are clustered with another DNA repair gene, such as phr or recN (gene clusters a and c in Supplemental Table 1 and Supplemental Figure 1). In the radiation-resistant cyanobacterium Arthrospira PCC8005, uvrBCD were found to be upregulated by gamma rays (no information is provided for uvrA ) (Badri et al, 2015). …”

“…Several P. marinus strains lack mutL, mutt , and mutY (Supplemental Table 1). In Arthrospira PCC8005 (radiation-resistant) mutST were upregulated by gamma rays (Badri et al, 2015). …”

“…This is true for Synechococcus PCC7002 and Nostoc PCC7120, where these duplicated genes can be studied and compared through deletion/over-expression. In Arthrospira PCC8005 (radiation-resistant), recGJQ were found to be upregulated by gamma rays (Badri et al, 2015). In contrast a few cyanobacteria has neither recJ nor recQ , as P. marinus MIT9515 (Supplemental Table 1).…”

Sustainable life support on Mars – the potential roles of cyanobacteria

“…Arthrospira sp. PCC 8005 cells were shown to be able to survive exposure to doses of at least 6.4 kGy of gamma irradiation, 1 kGy of He particle radiation and 2 kGy of Fe particle radiation (Badri et al 2015). Chroococcidiopsis spp.…”