Distinct distribution and evolutionary trajectories of pPolB1 and pPolB2 groups in the biosphere. a) A NCBI taxonomy tree with Eukaryotic taxa. The numbers in parentheses indicate the number of genomes having at least 1 copy of pPolB and the number of total genomes subjected to the Polinton pPolB search (see Materials and Methods for details). The sizes and colors in the pie charts indicate the copy number of Polinton pPolBs per pPolB-containing genomes and the classes of pPolB. b) A phylogenetic tree was constructed from multiple sequence alignment of pPolB proteins found in diverse taxa including viruses of prokaryotes, eukaryotes, DNA plasmids, and Polintons using the IQ-TREE-inferred ML method. Bootstrap supporting values are shown on the bottom positions of tree branches. All pPolBs identified in this study were found within Group 2 Polinton pPolBs where pPolB1 and pPolB2 classes form two major monophyletic groups. Asterisks indicated the Nematoda pPolB1 and pPolB2 proteins identified in this study.