Do Viruses Exchange Genes across Superkingdoms of Life?

Malik, Shahana S.; Azem-e-Zahra, Syeda; Kim, Kyung Mo; Caetano-Anollés, Gustavo; Nasir, Arshan

To evaluate these alternatives, we pooled the ABE FSFs of archaeoviruses (n = 93), bacterioviruses (319), and eukaryoviruses (315) into a non-redundant list of 442 FSFs (Table S6 ). Next, we dissected the 442 FSFs into seven new Venn groups: a (ABE FSFs detected only in the proteomes of archaeoviruses), b (ABE FSFs detected only in bacterioviruses), e (ABE FSFs detected only in eukaryoviruses), ab (ABE FSFs detected only in prokaryotic viruses), ae (ABE FSFs detected only in archaeoviruses and eukaryoviruses), be (ABE FSFs detected only in bacterioviruses and eukaryoviruses), and abe (ABE FSFs detected in archaeoviruses, bacterioviruses, and eukaryoviruses) (Figure 6 ). This classification enabled evaluation of virus-tovirus HGTs in contrast to either virus-to-cell or cell-to-virus candidate HGT events postulated above. The majority of the ABE FSFs were part of the be group (n = 130) once again suggesting relatively high activity of cross-superkingdom genetic exchange between bacterioviruses and eukaryoviruses (or their cellular proteomes) possibly driven by bacteria-eukarya lifestyle affiliations or, as an alternative, loss of these FSFs in archaeoviruses. The next larger groups included e (117) and b (102) (Figure 6) . These could represent direct HGT events from bacterial proteomes to bacterioviruses and eukaryal proteomes to eukaryoviruses, respectively.