Amoebae as Genitors and Reservoirs of Giant Viruses

Abstract

Amoebae are unicellular phagocytes that feed on microorganisms in their environment. Some amoebae have the largest genome size currently known on earth. They phagocytose any inert particle larger than 0.5 µm. Phagocytic amoebae can harbor different bacteria, fungi and giant viruses within the same cell. There is evidence of lateral gene transfer between the amoeba and its microbiological hosts. There is also evidence of gene exchange between viruses and bacteria hosted in amoebae. Moreover, there is evidence of gene transfer between viruses, such as Mimivirus and the virophage. As a consequence, viruses and intracellular bacteria living in amoebae have a sympatric lifestyle and large chimeric genome repertoires. We conclude that phagocytic protists continuously generate new species with chimeric repertoires that may succeed later if adapted to the environmental conditions and selected in a specific niche.