The effector protein Cas12e (formerly CasX) was identified in a collaboration between Jillian Banfield's and Jennifer Doudna's research groups at University of California, Berkeley using metagenomics sequencing in groundwater and sediment samples. Genomic database sequences show Cas12e present in two different phyla, Deltaproteobacteria and Planctomycetes. RNA-dependent interference activity by CRISPR-Cas12e was shown in E. coli by the ability of the system to inhibit DNA transformation in plasmid interference assays.Cas12d (formerly CasY) was identified in the same 2017 Nature publication, but found in the genomes of bacteria belonging to the Candidate Phyla Radiation (CPR).