Mutation adaptation and genotoxicity of microalgae induced by Long-Term high CO2 stress

This study determined that 60% is the most appropriate concentration of CO2 for the domestication of microalgae to obtain strains with improved flue gas CO2-adapting ability. The effect of long-term high CO2 stress (6–99% concentrations) on microalgal gene mutations was first clarified with genomic and transcriptomic analyses. The most beneficial long fragment indel/SV gene mutations in microalgae were obtained under 60% CO2. However, > 60% CO2 domestication caused genotoxicity of the microalgae cells via the following mechanisms: (1) it was not conducive to forming more stable long fragment indel/SV gene mutations, thus preventing further gene mutation; (2) gene mutations did not generate successful linkage to the regulation in transcription and translation; and (3) inhibition of the mismatch repair damaged the specialized ability of genetic variation, leading to the disrepair of harmful gene mismatches and fewer beneficial mutations. These novel results revealed that higher concentrations of CO2 for microalgal domestication did not necessarily result in microalgae that were tolerant to CO2 owing to the genotoxicity of long-term high CO2 stress. This conclusion informs futures efforts of domestication in the microalgae industry.