Project R-6391

Mechanisms of radiation resistance in Arthrospira sp. PCC 8005 (Research)

This project aims to provide a better insight on how certain genetic mechanisms or biochemical pathways allow the cyanobacterium Arthrospira to withstand extreme high doses of ionizing radiation (IR). Our main interest goes to strain PCC 8005 which is used as an oxygen producer and a nutritional endproduct in the lifesupport system MELiSSA and which is intensively studied by the MIC group of SCK-CEN. A first approach is to establish a catalogue of bacterial genes and proteins/enzymes known from literature to be involved in extreme radioresistance and perform bioinformatic analyses to identify genes and pathways relevant to IR-resistance in Arthrospira. This will also allow me to become familiar with the range of mechanisms for IR-resistance in other microbes. In addition, we will zoom in into particular protein sequences of strain PCC 8005 (e.g. ClpX, RecA, PriA, ..) to find clues for the Arthrospira sp. PCC 8005 IR-resistant phenotype on the molecular level (including protein motifs/domains). A second approach is to test IR-resistance in a wide set of Arthrospira strains. Through comparison of the available PCC 8005 genome data with genome data of IR-sensitive Arthrospira we hope to find additional genes and pathways potentially linked to IR resistance. Throughout these studies, particular interest will be given to DNA repair systems and the avoidance and detoxification of reactive oxygen species (ROS), as well as transcriptionally regulatory systems, including those that involve socalled non-coding RNA's (ncRNA's). In a third approach, Arthrospira sp. PCC 8005 cells will be subjected to high doses of gamma radiation and global gene expression levels will be measured by RNAseq technologies during at least one cycle of photosynthetic growth (i.e. in the presence of light, where previous gene expression experiments were only performed in the dark). Other gene expression experiments may be devised to address specific questions related to IR-resistance in strain PCC 8005. In general, irradiated cells will also be studied for DNA damage, protein modification, ROS abundance, and pigment and antioxidant composition. Novel antioxidants will be characterized and further investigated. A last aspect of the PhD project is to develop a genetic system for Arthrospira. Although Arthrospira has prominent defenses against incoming DNA this not only would allow the generation of gene-specific mutants of strain PCC 8005 to verify or test for an IR-sensitive phenotype but, in a more general way, would also give an important impetus to further genetic studies of Arthrospira.

01 October 2015 - 30 September 2019