Figure 1: The frequency of cas operons in different lineages.
From: Major bacterial lineages are essentially devoid of CRISPR-Cas viral defence systems
(a) Rifle groundwater metagenomic data sets and (b) NCBI complete bacterial and archaeal genomes. Only lineages with more than ten genomes are presented. Column heights are normalized for genome completeness, column colours represent CRISPR-Cas type, and the bold brown line represents the number of genomes. Blue vertical lines in a represent the fraction of genomes with CRISPR-Cas among NCBI complete genomes for applicable lineages. Two superphyla and four phyla in the groundwater samples, including the two most abundant ones, superphyla Parcubacteria (OD1), and Microgenomates (OP11), have an extremely low incidence of cas operons.
