Why does copper kill bacteria? Copper can kill bacteria by pulling electrons away from the bacteria’s cell wall, breaking it.
There are several materials and chemicals that are good at killing bacteria. Of all the metals, only copper, silver, and zinc can kill bacteria. Some plastics have been engineered to kill bacteria and there are some plants that can kill bacteria. These plants have been used in medicines since ancient times and there have been occasions were animals have been seen using them to run a wound. There are also a lot of molds and fungi that can kill bacteria as well, which is why we use them to make antibiotics. Although, the number of bacteria that are becoming resistant to antibiotics is increasing year by year and becoming quite a serious problem.
Before we look at how copper kills bacteria, let’s look at what bacteria actually are. Bacteria are single-celled, microscopic organisms. There is not one single type of bacteria, just like there isn’t a single species of animal. Bacteria constantly evolve and there is no way of knowing just how many species there are at the moment. Experts estimate that there could be trillions of different types of bacteria. We have names for 30,000 of these species. We also think that bacteria are all uniform, but they vary in size, shape, and what they do. The smallest bacteria that we know about is called mycoplasma genitalium and it is 200 nanometers long. The largest bacteria is surprisingly big. It is called thiomargarita magnifica and it is 2 cm long. It is so big that it can be seen with the naked eye. The one thing all bacteria have in common is that they are all single-celled organisms. And that is the only thing. Most of them have cell walls, but not all of them do. Many bacteria have flagella, which are microscopic hair-like structures that help them move, but not all of them do. Most bacteria reproduce through binary fission, which is where a cell splits into two identical copies, but not all of them do. They don’t all get energy in the same way either. Some break down chemicals to produce energy, but some can photosynthesize and make their own energy. They live in many different environments. It is safe to say that there is no single bacteria type, so when we talk about copper killing bacteria, we are only talking about some types of bacteria.
So, how does copper kill bacteria? There are three ways that copper can kill bacteria, and this also applies to other germs and viruses. The first way happens when copper rusts. Rusting happens when a metal is oxidized, which means it is exposed to oxygen. Oxygen atoms connect to copper atoms and they form a compound called cuprous oxide, which is copper’s rust form. Cuprous oxide is an unstable compound, which means it has an uneven number of electrons. Atoms don’t like being unstable If they have more electrons than they should have, they desperately try to lose one, and if they have fewer electrons than they should have, they desperately try to gain one. Cuprous oxide doesn’t have enough electrons, so it desperately looks for another electron and it finds it in the bacteria that are settled on it. Cuprous oxide pulls electrons out of the cell walls of the bacteria and the cell walls weaken. They can only lose so many electrons before they rupture and the bacteria dies. The second way also revolves around the bacteria’s cell wall. When copper and oxygen join together, they release free radicals, which are unstable atoms. Atoms of oxygen and hydrogen that don’t have enough electrons are released from the copper and they go looking for those extra electrons. They find them in the cell wall of the bacteria, weakening it. The third way is by poisoning the bacteria. Bacteria constantly evolve and adapt and they try to adapt to this copper world that is killing them. When they adapt, the bacteria takes in atoms from its surroundings, and those happen to be the very copper atoms that are killing it. Copper atoms get into the bacteria and prevent it from making energy, break its DNA, or disrupt other processes, until the bacteria dies.
Copper is so good at killing bacteria that a lot of companies are making copper glasses and bottles these days. This is not new knowledge. Ancient civilizations, such as the Egyptians and Greeks, knew about this property and they stored water in copper barrels and lined their water pipes with copper. If you do buy a copper bottle, you need to leave the water in it for about 8 hours to be sure that all the bacteria has been killed. Experiments on E-coli have shown how effective copper is. E-coli will survive on stainless steel for days, but 99.9% of it will have been killed after 2 hours on copper. Amazing. And this is what I learned today.
Try these:
Sources
https://blog.eoscu.com/blog/just-how-does-copper-kill-germs
https://en.wikipedia.org/wiki/Antimicrobial_properties_of_copper
https://www.medicalnewstoday.com/articles/157973
https://www.ncbi.nlm.nih.gov/books/NBK7637
Photo by Samer Daboul: https://www.pexels.com/photo/white-tea-cup-on-gray-surface-2102818/