Fig. 2

Viral life strategies in freshwater environments. Left: The Trojan horse strategy. A phage encoding the eukaryotic toxin ADP-ribosyltransferase (VIP2 family) infects a microbe that is then ingested by a eukaryotic predator (a flagellate is shown). In the phagolysosome, the toxin is expressed and released after cell lysis into the phagolysosome from where it translocates to the cystosol. In the cytosol, the toxin inhibits actino polymerization leading to cell death. Right: Phage-mediated ROS defense. a, b A phage encoding ROS defense genes, e.g., thioredoxin, glutaredoxin is ingested by a flagellate. c, d The damage produced to the microbe by the ROS present in the phagolysosome will be reduced by the expression of phage-encoded genes, which will favor survival during the oxidative burst. e When the phage-infected microbe is released outside, cell lysis by the phage can proceed