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
Everyones driven home the point about how the world is coated in a thin layer of bacteria, but one thing that’s important to consider is that only a tiny percentage of them have the potential to ever cause disease, and then an even tinier fraction of that number that are likely to cause you specifically to become ill – many bugs are opportunistic and will only make you ill under very specific circumstances.
Estimates vary wildly, but we can say with confidence that there are at LEAST 1 million, more likely 2-4 million species of bacteria. One study says there could be trillions. There are, at last count, exactly [1503 human pathogens](https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.001269). 25% of them have caused less than 3 cases. That means by the most conservative estimate, 0.15% of all bacterial species you’ll encounter could cause disease.
Of course, you’re more *likely* to encounter M. Tuberculosis than some bacteria from a hydrothermal vent in the deep ocean, but I just wanted to show that as a group, bacteria are for the vast vast vast part, harmless.
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