Viruses, Bacteria, Archaea, Protists, and Fungi

Abstract

Viruses, bacteria, archaea, protists, and fungi make up much of the biological world. Many of these are very small organisms known as microorganisms. Some are not organisms at all (e.g., viruses); others are not microscopic, though the parts recovered from archaeological sites may be small. Microorganisms are widespread and form the basis of food chains, contribute to nutrient cycling, and enhance soil fertility vital to the health of ecosystems. Some are restricted to specific habitats and are highly sensitive to changes in climates, water quality, and ecosystem processes. These provide direct and indirect information about environmental histories in aquatic and terrestrial landscapes of anthropogenic and non-anthropogenic origin. Some microorganisms have symbiotic or parasitic relationships with people or other organisms. Others are implicated in the deterioration of Paleolithic art at the Lascaux (Dordogne, France) and Altamira (Cantabria, Spain) caves, important World Heritage Sites (Saiz-Jimenez et al. 2011). Numerous species live in and on us, colonizing specific parts of the body and known collectively as a microbiome. Pennisi (2010) reports that 9 out of 10 cells in our bodies are members of this microbiome and that our own gastrointestinal system contains as many as 1,000 species.