Data from: The effect of bacterial mutation rate on the evolution of CRISPR-Cas adaptive immunity|CRISPR-Cas免疫数据集|细菌进化数据集

CRISPR-Cas immune systems are present in around half of bacterial genomes.
Given the specificity and adaptability of this immune mechanism, it is
perhaps surprising that they are not more widespread. Recent insights into
the requirement for specific host factors for the function of some
CRISPR-Cas subtypes, as well as the negative epistasis between CRISPR-Cas
and other host genes, have shed light on potential reasons for the partial
distribution of this immune strategy in bacteria. In this study, we
examined how mutations in the bacterial mismatch repair system, which are
frequently observed in natural and clinical isolates and cause elevated
host mutation rates, influence the evolution of CRISPR-Cas–mediated
immunity. We found that hosts with a high mutation rate very rarely
evolved CRISPR-based immunity to phage compared to wild-type hosts. We
explored the reason for this effect and found that the higher frequency at
which surface mutants pre-exist in the mutator host background causes them
to rapidly become the dominant phenotype under phage infection. These
findings suggest that natural variation in bacterial mutation rates may,
therefore, influence the distribution of CRISPR-Cas adaptive immune
systems.