They are less than a cell, yet they are one of the greatest manipulators of the world and are responsible for some of the worst diseases. They are viruses. This is somewhat different from the topics that this blog normally covers. However, a greater understanding of the world leads to a greater ability to meet the challenges that face us. Thus, this article will look at what viruses are, how they differ from bacteria, and how they work.
It is true that both viruses and some bacteria are pathogenic, however, there are some significant differences between them. They have a different chemical structure and what kills bacteria does not necessarily kill viruses. Viruses are strictly parasitic and are unable reproduce or carry out metabolic functions without a host cell. They are comprised of a submicroscopic particle of a nucleic acid genome (all genetic material surrounded by a protein coat called a capsid). The infective extra cellular form is called the virion and it contains at least one protein synthesized by genes in the nucleid acid of that virus. Some viruses also contain a lipoprotein membrane called an envelope. Viruses contain either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), but not both. DNA and RNA both contain genetic material with one chemical difference. (RNA has uracil instead of thymine). Bacteria, by contrast, are unicelluar organisms which contain both DNA and RNA. They reproduce through cell division and are not dependent on a host cell for biological functions. While bacteria can also be pathogens, there are also a number that perform important ecological functions, such as nitrogen fixing, which allows plants to absorb nitrogen from the soil. Without these bacteria, soil be fertile and organic matter would decay much more slowly. Viruses, however, are solely pathogenic. When a virion comes into contact with a host cell it attaches, penetrates the plasma membrane, and introduces its own DNA or RNA. Through chemical messages, the host cell is then “tricked” into sythesizing the virus’s genetic material which is then used in making new viruses. Eventually, the virus kills the host cell and goes on to infect other cells. Most viruses can produce between 100-1,000 new viruses in less than one hour. Hence, then can mutate very quicky and this one reason they can be so difficult to treat. COVID 19 belongs to the coronaviridae family of viruses, which is one of several. The corona virus has a club shaped glycoprotein spike in its envelope, which gives it a crown-like appearance (hence corona). Its genome consistes of a single strand of positive sense RNA. Positive sense RNA means that it acts as a synthesis for the translation of viral proteins.
There is some debate as to the origin of viruses and they were originally considered to be primordial life forms. However, this is not likely correct, since they need a host cell to metabolize and reproduce. According to Robert M. Wagner and Robert M. Krug, Encyclopedia Britannica April 2020, it is “likely” that viruses trace their origins to rogue pieces of nucleic acid. It is also “possible” that viruses came from plasmids, which are circular DNA molecules, without chromosomes. They could be transferred from cell to cell, acquired coded proteins to coat the plasmid DNA, and evetually have been converted into viruses.
According to Chambers Dictionary of Etymology, the word virus dates form 1392 and comes from the Latin virus meaning poison, sap of a plant, or slimy liquid. Related words are the Old Irish fi, the Greek wisos, and Sanskrit visa, all of which also mean poison. Its use as a disease causing agent was first recorded in 1728, the Chamber Cyclopedia. The word bacteria was first used between 1847 and 1840. It is from New Latin bacteria, French bacterie (1842), and Greek bakterion, meaning small staff or rod. Words are powerful and an understanding of the word can lend a greater understanding of what it names. When I looked these up, I thought it was interesting that bacteria, which can have good uses, is essentially named for its shape without any positive or negative connotations, while viruses which are solely pathogenic have a name rooted in disease.
As was stated earlier, due to their high reproduction and susequently high mutation rate viruses can be very difficult to treat. In addition, antivirals must kill the virus without killing the host cell. According to Wagner and Krug, effective antivirals must do one of the five following: prevent the virus from attaching to the host cell, uncoat the virus, prevent the sythesis of new viral components, prevent assembly of viral components, or release the virus from the host cell.
Viruses have the distinction of having a simpler chemical makeup than a living cell, yet they have achieved great evolutionary success. There is no doubt that the current climate is a difficult one. As of this writing, cases and deaths are continuing to increase, hospitals are overstretched, and tens of thousands of people are out of work as a result of the economic shutdown. If anything, this virus may convince us that we’re not as invincible as we’d like to think. However, with a greater understanding of what viruses are and how they are transmitted, we may be able to put long term preventative measures in place.