THREE GENE SOURCES IN DIATOMS. “The evolutionary trajectory of diatoms has brought together a highly unorthodox combination of genes derived by endosymbiotic gene transfer from two secondary endosymbionts to the exosymbiont nucleus, as well as by horizontal gene transfer that permitted numerous additional acquisitions from bacteria and Archaea.”
http://jxb.oxfordjournals.org/content/early/2012/01/20/jxb.err441.full