Abstract

Single Cell Sequencing Reveals Non-Random Genetic Alterations in a Cyanobacterium During the Biology and Mars Experiment (BIOMEX)

Yuguang Liu, Assistant Professor, Mayo Clinic

Understanding the impact of long-term exposure of microorganisms to space is critical in understanding how these exposures impact life during extended human missions. Here, we subjected Nostoc sp. CCCryo 231-06, a cyanobacterium capable of surviving in extreme conditions, to a 23-month stay at the International Space Station (BIOMEX, on the EXPOSE-R2 platform) and returned it to Earth for single-cell whole genome analysis. We used a microfluidic platform to isolate single cells, and amplify femtograms of DNA in a precisely controlled manner with minimal contamination, and sequenced their whole genome to identify the genomic changes in single Nostoc cells. The variant profile showed that biofilm and photosystem associated loci were the most altered, with an increased variant rate of synonymous base pair substitutions. We concluded that the combined effect of complex cosmic radiation and UV exposure may result in synergistic damage effects, with a higher number of synonymous variants with simultaneous exposure to cosmic and UV radiations. The cause(s) and evolutionary implications of the non-random synonymous genomic substitutions observed at the single cell level under long-term cosmic exposure warrants further investigation, and may revolutionize our views on how evolution occurs at the single cell, and also population level.