GIANT VIRUSES - A RELIC OF THE PAST AND CURIOSITY OF THE PRESENT

Abstract

Discoveries in Microbiology and its subfield Inframicrobiology – which is now known as the independent science of Virology – have always followed the same trend from larger microorganisms to increasingly smaller infectious agents. That held true until recently when scientists confirmed the existence of giant viruses. Although they were initially thought to be comparable to Gram-positive cocci, molecular biology technologies revealed their true viral nature. This new viral type is present in fresh and marine waters, and although commensal in humans, it contributes to human pathologies, especially lower respiratory tract infections – it represents the etiological agent of more than 20% of pneumonia cases without a precise etiology. These large, but paradoxically recently discovered viruses are ancient (as it is demonstrated by their re-awakening from the melting Siberian permafrost) and are leading researchers to question their ecological significance in direct connection with the global warming phenomenon and probable new emergent pathogens. The aim of this paper is to briefly present milestones in virology research and elaborate on the recently discovered senior viruses – giant viruses – along with their main characteristics, implications in human pathology, and ecological significance.