Not only do small heat-shock-proteins occur in eukaryotes and prokaryotes but they have also now been shown to occur in cyanobacterial phages as well as their bacterial hosts [2].

1: Crystal structure of a small heat-shock protein. Kim KK, Kim R, Kim SH Nature 1998;394:595-599. PMID:9707123

2: Analysis and phylogeny of small heat shock proteins from marine viruses and their cyanobacteria host. Maaroufi H, Tanguay RM; PLoS One. 2013;8:e81207. PMID:24265841