It is not possible to see microorganisms with our naked human eye. We need special equipment, like microscopes, to detect the great variety of tiny organisms that surrounds us. There is a whole world in a grain of dirt on the ground, filled with microorganisms like bacteria*.
Even though viruses** and bacteria are almost invisible to the human eye, they are nothing alike. The main difference is that viruses are not even alive. A virus is a dependent “parasite” that needs to infect a cell to survive. Thus, a virus contains genetic material but needs a living cell to provide the machinery for its replication. In other words, viruses need to infect a cell to “reproduce” and form new viruses.
In comparison, bacteria are alive because they can typically lead “independent” lives. Instead of infecting other cells to propagate, bacteria can reproduce by a process called binary fission, where they split apart to form two identical daughter cells. Depending on their membrane and structure, the bacteria can be classified as Gram + or Gram -. This is relevant to determine the type of antibiotic that will help when fighting a bacterial infection. Furthermore, there are many species of bacteria. For example, some use sunlight energy to survive, others break down waste, or help us digest food. Actually, many of them are good and do us no harm!
Although bacteria seem tiny in comparison to humans, they are giants compared to viruses. Bacteria have relatively complex machinery inside the cell whereas viruses’ structure is much simpler. Viruses are only composed of genetic material that is trapped inside a protein structure, which may or may not also have a layer of “fat” (the envelope) [1].
Lastly, viral and bacterial infections are also different. Examples of viral infections are COVID-19, polio, influenza, and AIDS. On the other hand, examples of bacterial infections are tetanus, tuberculosis, or strep throat. Interestingly, there is a kind of virus that is designed to infect bacteria, those bacteria-infecting viruses are called bacteriophages! [2] While bacterial infections can be treated with antibiotics, antibiotics cannot do any damage to a virus, which is why antiviral medication is needed.
Because antibiotics and antivirals are respectively for bacteria and viruses, it is important to go to the doctor to ensure that you are taking the right medication. Otherwise, you might take a drug that has no effect on the infection. More on this in the upcoming articles!
*Bacteria - microorganisms invisible to the naked eye that consist of a single cell, though they can group together to form colonies or biofilms. Some bacteria are pathogenic and cause disease, like Salmonella enterica, while others are beneficial to our health, like the ones normally found in the guts.
*Virus - it can be considered a very small and basic life form or an aggregate of molecules that is simpler than a cell. They can be found in the environment or inside living organisms. It has to infect a cell and use its machinery to multiply, since it cannot multiply by itself. Viruses consist of nucleic acids (DNA or RNA), a protein capsid that contains the nucleic acids and, sometimes, an external envelope of lipids. The flu, measles, AIDS and Covid-19, for instance, are caused by viruses.
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Written by: Nicole
Edited by: María and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. If you have any questions about this topic, please comment or send them to our email.
References:
What’s the difference between bacteria and viruses?. Imb.uq.edu.au (2021). Available at: https://imb.uq.edu.au/article/2020/04/difference-between-bacteria-and-viruses (Accessed: 9th June 2021)
Kasman LM, Porter LD. Bacteriophages. StatPearls (2021). Available at: https://www.ncbi.nlm.nih.gov/books/NBK493185/
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