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Decades ago I would stop by biology and biochemistry laboratories to see what was up, and I noticed a ubiquitous presence of a squirt bottle of bleach solution. When I asked what it was for I would get different answers in different laboratories. They ranged from disinfection of surfaces by accidental bacteria or phage contamination to denaturing of certain specific proteins or nucleic acids thought to be threatening to certain types of experiments.

Experimental techniques have developed dramatically over the subsequent decades.

Question: Are bleach solutions still routinely used in biology and biochemistry laboratories to rid experimental surfaces of bacteria, viruses, certain enzymes, and nucleic acids? If so, how can one solution be so reliably useful across all of these cases?

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I'm a research post-doc working in a US-based microbiology research lab. We still use a relatively low-concentration bleach solution to decontaminate most liquid cultures before disposing of them, but most of our surface and equipment decontamination is accomplished with alcohol (either ethanol or isopropyl alcohol (IPA)). We do work with some organisms that are not effectively killed by alcohol, such as C. difficile. C. difficile makes endospores which are very resistant to alcohol-based agents, but they are readily killed by bleach.

So after working with C. diff and other spore-forming bacteria we decontaminate with commercial wipes containing a stabilized sodium hypochlorite solution at a little less than 1%, which isn't even enough to give off a strong bleach odor. On metallic surfaces and some kinds of rubber, we follow up with an alcohol wipe to prevent corrosion from the bleach.

We do have other sporicidal agents that are used for specific applications where bleach isn't suitable, but most of them are much more harsh (requiring use of respirators), require a longer contact time, and have a substantially shorter shelf life at the effective concentration (sometimes just days or hours, vs. months with bleach).

Bleach is also good for destroying DNA and RNA in clean areas used for PCR setup, but there are some commercial products specifically designed to do this along inactivating nucleases that might degrade a sample, so I personally use those products. (Note that ethanol and IPA solutions can actually precipitate nucleic acids, leaving them behind after the solution evaporates.)

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I can only speak from my experience in many labs in different countries: We never used bleach for cleaning or disinfecting surfaces like cell culture hoods or lab benches. For this purpose we routinely used 70% Ethanol or commercial alcohol based disinfectants. Bleach was only used to inactivate culture media (cell culture and also bacterial cultures) so we could later discard it in the sink without the need to autoclave it (we usually had enough trash that needed this kind of treatment, so we didn't want to increase the amount further).

I think alcoholic solutions are used because they are more friendly to the skin if spilled, residues evaporate relatively fast and also because bleach is pretty aggressive to the surface, which can alter them possibly. There is also no need to remove residual bleach afterwards. However, for treating liquid waste, it was favorable.

Bleach can be used ultmatively because of its mechanism of action. It disrupts the cells and oxidizes its contents, so contaminants have no chance of reproducing anymore.

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    $\begingroup$ Thanks! From what I gathered in answers to How exactly does alcohol solution kill or neutralize viruses? (my own humble there in particular) alcohols are particularly good against viruses whose envelope includes lipids from the host's membrane, but may not be so effective against viruses that don't. But maybe those are not stable in the environment in general anyway? $\endgroup$
    – uhoh
    Nov 12, 2020 at 9:49
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    $\begingroup$ @uhoh They are at least not a general problem you encounter in the lab. If you suspect something like that, you would use a more suitable disinfection agent. $\endgroup$
    – Chris ♦
    Nov 12, 2020 at 10:13
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    $\begingroup$ I work in a C. diff lab where we have to decon benches and hoods with bleach wipes, as alcohol does not kill C. diff spores. We usually follow any bleach application with an alcohol wipe-down to prevent corrosion of stainless steel surfaces, like in a biosafety cabinet. $\endgroup$
    – MikeyC
    Nov 12, 2020 at 13:42
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    $\begingroup$ @uhoh the point isn't that the lipids come from the host, it's only that they are lipids. Their origin is irrelevant, all lipid membranes are susceptible to detergents or alcohol or other disinfectants. $\endgroup$
    – terdon
    Nov 14, 2020 at 15:39
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    $\begingroup$ @uhoh apologize? What in the world for? You didn't do anything wrong! I just thought that you had understood that the reason alcohol is effective against membrane-bound viruses is because they incorporate the host's lipids and I didn't want you to come away with that misunderstanding since alcohol would be effective against any lipid membrane whether it came from the host or not. $\endgroup$
    – terdon
    Nov 15, 2020 at 1:02
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Bleach also destroys DNA/RNA, and kills bacteria, making it useful in an area where PCRs are done. 70% ethanol is very friendly to DNA, but it kills bacteria well enough. My guess for the preference of 70% ethanol is that it is not as corrosive as bleach. Best would be bleach, and then a wipe of ethanol.

References

Use of bleach to eliminate contaminating DNA from the surface of bones and teeth

Improved ethanol precipitation of DNA

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    $\begingroup$ Best would be bleach, and then a wipe of ethanol. If you do this (the genetics lab I work in does), do a water rinse in between. Otherwise, ethanol and bleach can react to produce chloroform, which you don't want to breathe. Whether or not it would produce a dangerous amount, I don't know, but there's definitely no harm in reducing the risk $\endgroup$
    – anjama
    Nov 14, 2020 at 23:07
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I was associated with a lab in 2015 that used a lot of Streptococcus pneumoniae. They had ethanol squirt bottles to clean certain surfaces and in case of a spill. This was intended to kill that bacteria. In other labs previously I had seen bottles of hypochlorite (bleach) - but it was comical to see fungal growth in some of them due to the hypochlorite having decayed over time.

With regard to enzymes, (RNase particularly) the laminar flow cabinet stainless steel was wiped down with ethanol - not to denature any enzyme, but just to remove it and prevent remaining enzyme from becoming airborne.

Sorry for lack of refs yet

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    $\begingroup$ Yeah, people don't realize that hypochlorite is light-sensitive. I've fought a losing battle in a couple labs to store bleach solutions at least wrapped in foil or paper tape, if not in an entirely opaque container. I've found 1:10 bleach solutions dated several years previous that didn't even smell like bleach... $\endgroup$
    – MattDMo
    Nov 12, 2020 at 19:28

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