October 19, 2021
Viruses (from the Latin virus, "poison" or "toxin") are small infectious agents, most with a diameter of 20-300 nm, although there are viruses (0.6–1.5 µm) that have a constituted genome. of one or more nucleic acid molecules (DNA or RNA), which are either single-stranded or double-stranded. Virus nucleic acids are usually coated with a protein coat made up of one or more proteins, which may also be coated with a complex envelope made up of a lipid bilayer. Viral particles are extremely small, submicroscopic structures. Most viruses have small sizes, which are beyond the resolution limits of optical microscopes, and it is common for their visualization to use electron microscopes. Viruses are simple structures, compared to cells, and are not considered organisms, as they do not have organelles or ribosomes, and do not have all the biochemical potential (enzymes) necessary to produce their own metabolic energy. They are considered obligatory intracellular parasites (a characteristic that prevents them from being considered living beings), as they depend on cells to multiply. Also, unlike living organisms, viruses are unable to grow in size and divide. From host cells, viruses obtain: amino acids and nucleotides; protein synthesis machinery (ribosomes) and metabolic energy (ATP). Outside the intracellular environment, viruses are inert. However, once inside the cell, the replication capacity of viruses is surprising: a single virus is capable of multiplying, in a few hours, thousands of new viruses. Viruses are capable of infecting living beings from all domains (Eukarya, Archaea and Bacteria). In this way, viruses represent the greatest biological diversity on the planet, being more diverse than bacteria, plants, fungi and animals combined. Nearly 200,000 different types of viruses spread in the world's oceans, according to one study. The 2019 count is 12 times higher than the previous census of marine viruses recorded in 2016. There are, individually, about ten nonillions (10³¹) of viruses on planet Earth, a number one hundred million times greater than the number of stars on Earth. observable universe.