The Virosphere: How Viruses Move Genes Across Life

In 2017, microbiologists used the term virosphere for all viruses and virus-like elements on Earth. Most have never been grown in a laboratory. They occur in seawater, soil, the human gut, ice, hot springs, and deep mines. A single metagenomic sample can hold thousands of viral sequences that existing databases have not recorded.

Viruses have no cellular structure and usually cannot make energy on their own. They carry genetic material into a host cell, then use the cell's machinery to make copies. That is why viruses are often described as pathogens. The same process of packaging and transport can also carry a piece of one cell's genome into another cell.