About the differences between bacteria and viruses

Considering the current situation about Covid19, family and friends asked me about the actual difference between viruses and bacteria. A question which I generally love to give a lecture about.

So I used the time throughout social distancing to compile some facts and help you understand this time of crisis.

The main difference between a virus and a bacterium is:

Bacteria are considered living organisms – viruses not.

This is because:

Bacteria can grow on their own by cell division. Viruses require host cells for their production.

Bacteria can produce their own energy by metabolising nutrients, meaning digesting food. Viruses are unable to do metabolism.

Bacteria can be highly complex, talk to each other and adapt to the environment, import and export molecules. Viruses are not able to adapt to their environment on a metabolic level.

Bacteria have a cell wall or a double cell membrane which protects the inner content of the cell from the environment. The viral envelope is like a coat made of proteins and lipids. These lipids come from the host cell that originally produced the virus particle.

the visual differences between bacteria and viruses

The bacterial cell is filled with proteins, ribosomes and all the “stuff” the cell needs to grow, divide, produce anything. A virus is only filled with DNA or in the case of Covid19 with RNA.

When a bacterium infects a cell, it still works as an organism. Viruses break into its single particles which release its genetic material, which can be DNA or RNA. The DNA/RNA then tricks the host cell into reading the virus DNA/RNA. This leads to production of the virus complexes. When the host cell produced enough virus complexes, it assembles to a full virus particle and leaves the cell.

The virus replication cycle adapted from BioRender. Update on 16/03/2020: Viral RNA is being transcribed into different species of positive and negative sense subgenomic RNA and not, as stated before, into DNA.

In any case a virus requires a host. Without a host, no virus will survive. This is why throughout evolution, viruses evolved that are highly infectious. Thus, the virus easily spreads and more and more virus can be produced.

As I keep reminding, every kind of organism always wants to survive.

Most bacteria can actively move or swim with their flagellum. Viruses do not have such mechanism and require spread by host acceleration. For example one such mechanism is sneezing. When we sneeze, we accelerate the virus out of our body and into a different host – a common spreading mechanism by viruses.

Another important difference is that most of the us known bacteria actually help our organism, can be considered as “good” bacteria. No virus is actually advantageous for a host, as it always hijacks the host machinery to produce more and more of the virus. And in most cases this is deadly for the host cell.

Antibiotics only work against bacteria, because they tackle different mechanism within the bacterial cell – read more about this in this article about antimicrobial resistances. Viruses do not have these targets for antibiotics, which is why they would be useless.

Viral infection can be treated by anti-viral drugs, which work differently than antibiotics. And for not many viral infections do exist anti-viral drugs. For Covid19, so far no anti-viral drug has been found.

Virus infection can only be prevented by vaccines. These vaccines recognise surface proteins within the coat of the virus. Because the surface of bacteria is different, a vaccine against a virus will not work against a bacterium and the other way around. So, the pneumococcus vaccine will not actually prevent from the Covid19 virus, but prevent you from a pneumococcus infection, which are bacteria.

Also, generally viruses are a lot smaller than bacteria. However, there are always exceptions. Giant viruses have been found and so have been tiny bacteria about the same size ac the common virus.

The corona virus is very small, which makes it so light that it can travel “through air”. This again, makes it very infectious and you should keep a safe distance of about a meter from anyone infected.

These are the main points so far and what remained from my undergraduate lecture on virology a few years ago.

Now, in a healthy person, usually your immune system can fight the Covid19 similarly to any other cold virus, even though your symptoms are most likely different from that of a flu. Eventually, your body will make antibodies against the virus and you will easily overcome this infection. However, in immune-compromised people, the immune system might not work this well and they will have problems fighting off this virus.

Since this is a very new issue, we do not really know much about what is going on and scientists are currently trying to understand the molecular details of Covid19 infection.

Some more information can be found in this article by Nature interviewing the director of the Wellcome Trust Foundation Jeremy Farrar.

Okay, now what about the soap issue?

For this I can highly recommend this article which explains very detailed the science of soap and how it is working against the virus.

 Soap molecules have a dual nature. One end of the molecule is attracted to water and repelled by fats and proteins. The other side of the molecule is attracted to fats and is repelled by water.

Think about what happens when you pour some olive oil into water. The oil pools up in a mass that floats. “That’s because fats don’t mix with water,” he says. But mix some soap into the oil and water and the oil will disperse. Basically, that happens because the soap is attracted to the grease, via its fat-loving side, but then tears it up, pulling it into the water via its water-loving side. It’s a one-two punch. Surround the oil particles and move them away from one another.

Coronaviruses are a bit like the oil mentioned in the above example: bits of genetic information — encoded by RNA — surrounded by a coat of fat and protein.

One side of the soap molecule (the one that’s attracted to fat and repelled by water) buries its way into the virus’s fat and protein shell. Fortunately, the chemical bonds holding the virus together aren’t very strong, so this intrusion is enough to break the virus’s coat. “You pull the virus apart, you make it soluble in water, and it disintegrates,” he says.

Quote from the article “How soap absolutely annihilates the coronavirus” on Vox.com

And here is a podcast about the science of soap by “But why”

Explaining Coronavirus to Kids and the Science of Soap.

I also compiled some information on the Covid19 virus.

Please, if you have any more questions or comments or would like to add important information, send me a message or comment in the text boxes below.

Also, share the information with your friends and family and anyone who you think might be interested. Looking forward to any comments!

A great overview about the coronavirus


About the fact that Covid19 is not just like the flu virus.

How soap destroys the virus by @AjSadique

The WHO now even started a SafeWash challenge to keep everyone’s hands clean

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