I always hear about how poisons have a short life span. Rats, cockroaches, bacteria evolve so that future generations are unharmed by today’s toxins.
So why does bleach remain effective? Same thing for DDT, same for mouthwash.
Pretty much the same reason that humans haven’t developed an immunity to being thrown naked into a vat of strong alkali.
Bleach is a physical assault on bacteria. It doesn’t stop them from reproducing or repairing cell walls like antibiotics can; it physically destroys them.
An organism might be able to mutate and become immune to things which are only subtly interfering with its life but it cannot develop an immunity to something which radically affects it. There is no way an organism can develop immunity to a chemical which just totally destroys every sign of life just like birds cannot develop immunity to bullets.
Some organisms do have natural defenses that give them * some * protection against bleach and other chemicals. For example, giardia has a hard shell that protects it (to some degree) from bleach. Other intestinal parasites may have waxy coatings or other mechanisms that protect them from being digested on their way to your all-you-can-eat intestinal buffet. In these cases, it’s not a stretch to think that the organisms could evolve to survive a wider range of chemical attacks.
resistant coats can be developed, but at quite a cost. They generally interfere with absorbing and excreting substances, and are very energy-intensive to produce. Lots of reasons to have such a trait selected against, not many reasons to be selected for.
It helps to understand that there are two different sorts of things we use to kill germs. On the one hand, you have broad-spectrum poisons like bleach. Bleach kills everything, and very well, too. Sometimes, that’s great. But sometimes, you need to be able to kill the germs without killing your kids, or pets, or garden, or whatnot. Then, you need something specific. Ideally, you want something that kills all of the harmful species, but leaves all of the harmless species untouched. The problem is that some of the harmful species can be very similar to some of the safe ones, so it doesn’t take much of a mutation for one to develop immunity.
If there were environments where bleach occurred naturally in a variety of concentrations, I wouldn’t be all that surprised to find some kind of life there; certainly there are other environments (boiling pools of acid, for example) that are generally harmful to life, yet a few lifeforms have evolved defences.
How, precisely, does bleach kill bacteria? Bleach is a 5.25% solution of NaOCl, and it only takes a few spoonfuls of that mixed with a washer full of water to disinfect your laundry, so it must be very potent. However, if you stick your hand in a cup of bleach, your skin won’t melt off, so it can’t be THAT potent. (Of course, you’d want to wash your hands right away, but it isn’t like sticking your hand into acid.)
Your skin won’t ‘melt’ off, but it doesn’t take that strong a solution to make your skin blister and dry out (from personal experience, I can tell you), which is well beyond the scale of microscopic organisms like bacteria. Bleach reacts very strongly with organic compounds. Imagine the cell wall of a bacterium to be like two staggered rows of Lego blocks, holding each other together. Bleach is like coming in there with a hammer and busting it up.
I asked a Microbiologist in my lab this a while ago - specifically how does ethanol kill bacteria, and how does bleach? He told me that the bleach chemically modifies the surface of the bacteria since it has that reactive oxygen, while the ethanol gets inside the membrane and causes damage. I assume bleach (Na-O-Cl) is O-Cl in solution. The chlorine, due to it’s high electronegativity, will pull the electrons away from the oxygen making it want to react even more. This must attack something on the bacteria. I’m not sure of the ethanol mechanism.
Well that wasn’t completely right or wrong, I just found this via Google:
And this regarding ethanol:
Could this be similar to Boric Acid. I have tried a lot of things on roaches but boric acid WORKS. It takes awhile but the roaches never seem to get used to it like other products. Is that because they don’t ingest it rather they walk thru it?
Boric Acid kills because, as I recall, it causes micro abrasions on the shell of the roach which cause its body to dry out. I will find you a link.
Seems that is just one of two possibilities, but both result in dehydration.
since depending upon the source that you read prions, can resist even autoclaving at high temperatures for relatively long periods of time. Are these living organisms? Probably not, but maybe in the sense that a virus is an “organism”. Though they are merely proteins prions may cause diseases ranging from scrapie in sheep to Kuru, variant CJD, and some cases of sporadic CJD in humans. In addition, there is a disease termed chronic wasting disease found primarily in elk that may be prion based.
That may be my all-time favorite SD column … “Now, you may regard borax as ‘pansy-ass,’ my boy, but that is because you are young and ignorant and have not yet grasped the subtleties of Total Insect Warfare, which requires fanatical dedication. You must mix up oodles of this stuff and apply it with the enthusiasm of Robert S. McNamara dumping Agent Orange on the Mekong Delta.”
How come we don’t see columns with this kind of genius anymore?