When I was a kid, my parents told me that everyday items are always filled with bacteria, such as banknotes, tabletops, keyboards, smartphones, floor (pick up your fallen food within 5 seconds or it will be infected with bacteria), I grew up told there are millions of bacteria under the fingernails all the time, is this really true? How can they be always there and survive that long if they are on the floor, banknotes etc.? They are living organisms, need to eat something, right? For my thinking there is nothing to eat on the banknotes normally. Can anyone bust this myth or confirm? Thanks in advance.
In: Biology
Yes, everything is “covered in bacteria”, but a lot of them are dead or dying, or in “suspended animation” hoping to get lucky and start growing again.
(Some are better able to survive long-term drying-out and exposure than others, and have different survival strategies, way too complex for ELI5 and frankly beyond my expertise. But overall, the fact they’re so simple compared to eukaryotic cells (cells with a nucleus, like most living things that aren’t bacteria) means they’re able to survive stuff that would kill cells of higher organisms or cause them to commit “suicide.”)
If something is coated in a large amount of bacteria, it’s going to be nasty/slimy (“biofilm” is the technical term), and a seriously bacteria-infected liquid is going to look very cloudy. But at that level, you’re probably talking about trillions of bacteria. (or more)
You know the film that forms on your teeth over the course of a day? Ever scratch at it with a fingernail and wonder what that off-white stuff is? Yeah…
A few million bacteria is nothing, because they’re tens of thousands or hundreds of thousands of times smaller (in terms of volume) than human and other higher animal cells. A bacterial “colony” the size of a largish grain of sand might contain over a billion cells.
So most of the ones coating everything don’t have the right conditions to grow (divide), which is why everything isn’t actually coated in a thin layer of disgusting slime all the time. 🙂
But because a bacterium typically needs less than one hour to divide if it has the nutrients, their numbers can increase exponentially very rapidly if they manage to find the right environment. (Although the human body is typically not a welcoming environment, because of our immune system and our own symbiotic “microbiome” which competes with any foreign interlopers.)
Anyway, so long, I just realized I need to brush my teeth…
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