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  • Alex Cloherty

Bacteria vs. Viruses - what's the difference?

Updated: Nov 9, 2021

Oftentimes on this blog, I refer to 'microbes' in a general sense. For instance, I call both bacteria and viruses "microbes". But, although they can be grouped together as "microbes" they are different from each other in many ways - like cats and dogs are both housepets, but different. The umbrella-term "microbes" includes several different groups of related and unrelated small things, that are really only grouped together as "microbes" because they are small and hard to see with the naked eye. For instance: viruses, bacteria, fungi, and amoebas would all be "microbes". So, what are the differences, then? For now let's focus in on the ones we hear about most in the news: viruses, versus bacteria.

Today's mini-Microbial Mondays was inspired by a question from Tine. Thanks to Tine for the inspiration!

As I began to write this, I realized once again that it is rather a difficult task to explain the difference between viruses and bacteria. But, to put it simply, scientists typically consider bacteria to be single-celled living things, which have a fatty "cell membrane" - a sort of skin that encloses them - but no nucleus.

Ok... But what's a nucleus?

A nucleus is a specific place in all animal, plant, and fungal cells that acts sort of like a control center, and the presence or absence of a nucleus is considered a main difference between bacteria and so-called "eukaryotes" - i.e. animal, fungal, and plant cells. As an aside, "eukaryote", this scientific blanket term for animal, fungal, and plant cells, actually means "true nucleus", underlining how important this part of the cell is. As well as a nucleus, animal, fungal, and plant cells also have other specific organs (called organelles) that bacteria don't have, like the famous powerhouse of the cell, mitochondria. But back to bacteria.

Like plant, animal and fungal cells, Bacteria can also "replicate" (reproduce) without the need to hijack another living creature. Viruses, on the other hand, are usually defined on the basis of them absolutely needing to hijack another cell (it can be, for example, a plant, bacterial, or animal cell, depending on the virus) to reproduce. In other words, a virus can't have virus babies until it's hijacked something else to incubate in. I like to compare viruses to the Alien in the 1979 sci fi film: they need living incubators.

But here is the maddening (and fascinating) bit: there are exceptions to that rule!! For instance, the bacterium that causes chlamydia needs an "incubator", just like viruses do.

I guess I would summarize the whole thing like this: when we don't think about it too hard, scientists consider viruses versus bacteria to be completely different - like dogs versus cats. But in reality, they can be trickier than that to categorize because there is some gradient between their characteristics. Like a chihuahua: small like a cat, barks like a dog, and overall a strange small animal that is harder to characterize than, say, a St. Bernard. Having said that, though, in general viruses are much less self-reliant than bacteria, which have many more features that allow them to live life all by themselves - whereas viruses need a host.

That's all for today - but I do have some more jargon-free science for you this week. This week, I am representing the Netherlands in an international science communication contest called "FameLab". This Wednesday, on November 10th, the international semi-final that I am in is streaming live here on YouTube, at 16:00 GMT (or, 08:00 Vancouver time, 11:00 Ontario time, 17:00 Dutch time, and other times can be checked here). This first of two semi-finals (Semi-final #2 is the following day at the same time, same place) will feature top science communicators from around the world, each explaining a different concept in easy-to-understand language, in three minutes.

A few of us will go on from this competition to to the finals - and the audience gets to choose! A link to vote on your favourite communicator will go up at the same time as the livestream, and stay up for 24 hours for you to pick your top 3 communicators to head to the finals. I would love it if you would watch - the finals will also stay up on YouTube to watch at a more convenient time if that is better for you - and vote for whoever captured your imagination most. As a little sneak preview - I'll get back to that similarity between some viruses and a certain 1979 sci fi film. Hopefully, see you there!

So - until Wednesday,

~ Alex

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