Studies on the response to spaceflight related conditions in the cyanobacterium Arthrospira sp. PCC8005 using a genomic approach.

Due to its efficient oxygen production and its valuable nutritional properties, the cyanobacterium Arthrospira sp. PCC 8005 has been selected as oxygen producer and food source in the bioregenerative life-support system MELiSSA, developed by the European space Agency (ESA) for future long-term space missions. In space, ionizing radiation might have an effect on the genome and the metabolism of this organism. In this thesis a first draft of the complete genome of Arthrospira sp. PCC 8005 was obtained. Its nutritional value was assessed by reconstructing the biosynthesis pathways of all essential amino acids, the essential fatty acids linoleic acid and γ-linolenic acid, and some vitamins. No biosynthesis for cyanotoxins were detected so far. Arthrospira sp. PCC 8005 presented a promising resilience to oxidative stresses induced by H2O2 and ionizing radiation. Exposure to high acute doses of gamma radiation up to 3200 Gy did not affect the cells. Acute doses of gamma radiations above 200 Gy induced a decrease in the growth rate of the cultures. Arthrospira sp. PCC 8005 did not show any effect of chronic low doses of neutron and gamma radiations. Multiple exposures suggested a putative adaptation to chronic low doses of radiation.