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sergius
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hydrogen peroxide
why is hydrogen peroxide is toxic to bacteria and yeasts?
Ideally it is decomposed by enzymes like catalase to oxygen.
The oxygen should be useful for respiration of bacteria/yeasts.
But why bugs perish when exposed to even minute concentration of hydrogen peroxide?
can any one explain?
Sergius
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tom haggen
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Ok lets say hypotheticlaly your eyeball is a living organism for example. Use some 30% hydrogen peroxide for eye drops and see if your having a bad
day. Now imagine your eye is a micro organism. Less concentrated H2O2 is going to have the same effect because it takes less moles of H2O2 to do the
same damage.
PLEASE DO NOT USE H202 AS EYE DROPS!!!
Or do if it will prevent you from being able to see a computer screen and ask stupid questions.
In my defense, I wouldn't have flamed this idiot so much if he could correctly spell the word "catalyses".
[Edited on 16-11-2004 by tom haggen]
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The_Davster
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Tom, he was not even trying to spell catalyst. Catalase is a natural enzyme in all animals(is it in plants too?) that decomposes the H2O2 produced
during cellular processes to hydrogen and water.
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tom haggen
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ok well I guess i don't have a good excuse. Ok well hydrogen peroxide is corrosive to living organisms. Sorry I don't have an equation for
this reaction.
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BromicAcid
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Not only will it randomly oxidize things that a certain bacterium might need to live, but there are many nasty anaerobic bacteria that the oxygen
formation will wipe out.
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chemoleo
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Tom, I don't quite see why your 'flaming' is warranted, particularly that you don't know what catalase is ... might be good to
check your textbook before your next flaming attempt 
Anyway.......
H2O2 is definitely not useful as such to any organism, as it produces much harm onto the way to the mitochondria, where the O2- ion is produced, and
even more harm once it arrives. The O2- is indeed broken down by various enzymes, and its energy is employed by the electron transport chain. O2-,
however, also contributes to much radical damage - which is in part why we age with time, and why it is often said that low calorie food is good for
you (your mitochondria are less active, and thus produce less O2-/OH.).
It is of course more harmful to small organisms as it rapidly is able to diffuse into the whole cell/organism, thereby killing it (i.e. overwhelming
the mitochondria, which thereby die of oxidative damage).
H2O2 should be, per unit bodymass, equally toxic to most organisms - as its detrimental effects are the same in any organism. Of course various
effects come into it, i.e. some may be better at absorbing H2O2, and thus die faster, or have greater damage - while others have a better ability to
break down peroxides.
If you drink H2O2, it shouldnt be doing THAT much damage as I should think it is broken down by oxidising food stuff in the stomach. Not that I'd
try it. However, you may remember that guy who got MEKP onto his trousers... and had massive headaches and other symptoms afterwards. That is
definitely very dangerous as this peroxide is (due to its hydrophilic nature) able to diffuse accross fatty acid membrane layers, i.e. straight into
mitochondria/nuclei, and achieve the damage there much more rapidly.
Sergious, any biochem textbook explains where the superoxide radical/ion is, and what it does, it maybe best if you have a look there, for furhter
details.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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tom haggen
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Alright I take it back.
Sorry midterms are making me grumpy.
[Edited on 16-11-2004 by tom haggen]
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HNO3
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Aren't yeast anaerobic? that is, they can't survive with much O2 in their envirovment.
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Esplosivo
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| Quote: | Originally posted by HNO3
Aren't yeast anaerobic? that is, they can't survive with much O2 in their envirovment. |
There are two types of anaerobes, the obligate ones which cannot survive in the presence of oxygen, and the facultative anaerobes which can survive
through a range of oxygen concentration ranging from common air conc. to no oxygen at all. Yeast is a facultative anaerobe and therefore can survive
in the presence of oxygen, carrying out aerobic respiration and in its absence carrying out anaerobic respiration - producing ethanol as a byproduct.
This latter property is used in the production of alcoholic beverages.
Theory guides, experiment decides.
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chemoleo
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Now, now, whats this about? The point being?
If yeast were solely anaerobic, it wouldnt NEED oxygen to live, and the presence of oxygen might be detrimental to survival.
Anyway...yeast can both live with or without oxygen.
In the case of brewing it lives anaerobically, producing ethanol (or lactate). In the presence of oxygen it'd ferment this on to CO2, and acetic
acid I guess. Regardless, the superoxide radical O2-. is present in both - as part of the normal electron transport chain in the mitochondria. The
O2-. is normally converted by superoxide dismutase (an enzyme) to H2O2, which is less damaging, which in turn is then disproportionated to H2O and O2
by catalase. You can see that if the catalase/superoxide dismutase are overwhelmed, it very rapidly can kill the electron transport chain, and thereby
the energy supply of the cell (apart from mutagenic effects etc).
So, aerobic/anaerobic - no matter, H2O2 is bad for either.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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sergius
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Interestingly when I searched in the Google, I got several links which say that hydrogen peroxide can be a source of oxygen in mould cultivations!!
A few of them are given below.
http://www.mycomasters.com/Advantages-FAQs.html
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=Text&D...
http://members.aol.com/PeroxyMan/
What I sincerely believe is that hydrogen peroxide is converted to highly toxic reactive oxygen species such as hydroxyl free radical by transition
metal ion mediated catalysis.
But the enzyme catalase secreted by the molds into the growing medium may decompse the hydrogen peroxide to molecular oxygen and water. The molecular
oxygen may be useful for the respiration of pelletized molds.
If you put some amount of hydrogen peroxide in a solution containing catalase you can see bubbles of oxygen coming out. You can even measure the
amount of oxygen produced when some living yeast is present in that solution. There are so many interesting experiments involving oxygen generation
through catalase mediated catalysis of hydrogen peroxide breakdown.
Even in waste water treatment plants hydrogen peroxide is used to incerase the oxygen concentration so that harmful anaerobic microoragnisms are
killed.
Sergius
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sergius
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hi there,
some more links on oxygen supply and hydrogen peroxide
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&a...
http://www.h2o2.com/intro/overview.html
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&a...
From these can we make an assumption that hydrogen peroxide can be a source of oxygen other organisms also if they are sufficiently armed with the
enzyme catalase ( by external addition or engineering the organism to make more catalase in side the cells and/or by secreting it out)?
Sergius
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Wolfram
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Q
As I see It H2O2 should be cancerogenic and very dangerous but it isn´t known to be very dangerous, why?
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chemoleo
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Sergius, good links.
It's interesting that it is used for mushroom growing (now that must be of use to some mushroom growers here), and it's also interesting to
see that it is used as a sterilising medium - meaning that nothing else can grow! Seems the mycelium is producing plenty of catalase.
Do remember though, H2O2 is used as a disinfectant, again emphasising its toxicity to microbial organisms.
Not just that, it is clearly toxic to humans too.
Check this for instance:
http://www.atsdr.cdc.gov/MHMI/mmg174.html
H2O2 vapours cause significant morbidity!!!
If ingested, solutions of hydrogen peroxide up to concentrations of 9% are generally nontoxic (nonfatal); however, even a 3% solution is mildly
irritating to mucosal tissue and may cause vomiting and diarrhea. Ingestion of industrial-strength solutions (≥10%) causes systemic toxicity and
has been associated with fatalities.
HOwever, it is not classified as a carcinogen.
Anyway... i would once again like to point out the increased toxicity of organic peroxides that are lipid soluble. The mechanism of
action is the same (radical formation, oxidation of cysteines, metal ions, lipid peroxidation etc), - see http://www.cdc.gov/niosh/pel88/1338-23.html
Ingestion is often fatal. It is, however, not a carcinogen, either (which is good to hear).
To sum this up - H2O2 is toxic for ANY organism, if administered in high enough concentrations/amounts. There is a certain level of tolerance due to
restricted uptake rates, but beyond it becomes quickly lethal. For instance, injected H2O2 is tolerable up to the point where the O2 generated (via
catalase and others) is no more soluble in the system fluids. Then this becomes lethal, death by embolie.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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sergius
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This link may of interest to those anxious about cancer and ageing.
http://www.cnn.com/2004/HEALTH/11/17/health.apples.reut/inde...
Sergius
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Alagebrium
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Some micro-organisms, like some Lactobacilli produce H2O2. It suppresses the growth of several pathogens, so H2O2 isn't all bad after all.
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Blind Angel
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I remember reading that a bug is able to produce a poison constitued of 28% H2O2 as a protection weapon (www.lachimie.com if you can read/understand french, there are a lot of info on H2O2)
/}/_//|//) /-\\/|//¬/=/_
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BromicAcid
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The Bombardier Beetle has a pair of glands that produce large quantities of hydrogen peroxide and hydroquinone. When threatened it allows the two to
react producing quinone and water and lots of heat, it sprays out the mixture which is boiling or close to it, making an audible sound as it does so,
it contains enough of each chemical to do this 20 - 30 times in quick succession. In addition to any heat or residual peroxide or even the sound, the
quinone produced deters other insects from getting up close and personal. From an entry in 'Chemistry' 6th edition by Raymond Chang.
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Wolfram
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When I read about this beatle I wonder why nature yet has not developed a creature with natural flamethrower like device. Very interessting would be
to know how this beatle prevents the H2O2 from harming it self.
[Edited on 19-11-2004 by Wolfram]
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Blind Angel
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I already read somewhere that it would be possible, if the creature had two gland on the side of the mouth and a pouch containing small amount of
white phosphorous and small lenght alkane or alcohol. The site was looking at the existence of dragon on a scientific way (not that they exist, but
could they exist, with body mass and all)
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sergius
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Hello everyone,
The toxicity of hydrogen peroxide is absolutely dose dependent. The toxicity of hydrogen peroxide is mediated by frre radicals generated when there is
excess of molecular oxygen present at a particular locality.
We all know that the solubility of oxygen is very poor and it amounts to 8 ppm at 25 deg C. This is more that sufficient to meet the oxygen
requirement of microbes in the aqueous media.
The decomposition of hydrogen peroxide (mediated by catalase) occurs in liquid phase as follows
2H2O2 -------> 2H2O + O2
By liquid phase decomposition is meant that what ever molecular oxygen that is formed is in solution.
Stoichiometrically, when we decompose 1 mM hydrogen peroxide, it will give 0.5 mM of oxygen ie (16 ppm of oxygen twice that of equilibrium
concentration at 25 deg C). Hence much lower concentrations can be safely used for oxygen supply. The catalase here will be playing the lead role
minimising the risk of free radical generation by converting hydrogen peroxide into molecualr oxygen.
Depending on the sensitivity of the microorganism to hydrogen peroxide and oxygen the concentration can be optimized.
I hope this method can be very much useful in industrial biotechnological processes, where the cost for meeting the oxygen requirement is very very
high.
An oxygen cylinder costs more than 100 times that of 500 ml 30% hydrogen peroxide. Hence this may be promising technology in industrial scale.
Sergius
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unionised
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"An oxygen cylinder costs more than 100 times that of 500 ml 30% hydrogen peroxide. Hence this may be promising technology in industrial
scale."
Erm..., where are you getting those prices from?
The catalogue I have lists H2O2 at about £15 and I don't think a gas cylinder of oxygen costs £1500.
BTW, if I remember rightly, the white blood cells generate H2O2 to destroy invading bacteria.
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sergius
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Oops... sorry about the wrong price details. But the cost difference will be very significant at industrial scale of operation.
The concentration of commercially available hydrogen peroxide is 30% which works out to a molarity of ~ 9.7 M. The working concentration of hydrogen
proxide will be between submillimolar to millimolar range. So the quantum of oxygen required will be effectively met with a single hydrogen peroxide
container, for which one currently needs a few cylinders of pure oxygen in addition to continuous operation of high power consuming air compressors.
The toxicity of hydrogen peroxide is well documented one. The concentration employed for oxygen supply strategy is much less than that of
inhibitory/lethal concentration. hence toxiciyt may not be an issue of concern. The critical thing is to monitor and control the hydrogen peroxide
concentration at desired levels below toxic concentrations.
Sergius
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White Yeti
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It's really quite simple, hydrogen peroxide is dangerous to living things because it is a strong oxidizing agent, just like fluorine and ozone. It
destroys DNA.
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brocklee
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i believe that the specific ways it can damage DNA are through oxidizing bases of the nucleotide causing replication blocks and mutations (eg
8-oxo-guanosine and cytosine to uracil through the deamination) and conversion of dNTPs to rNTPs by oxidizing the 2'OH (which increases the
probability of strand breaks).
Also as people mentioned oxidation of lipids and proteins causes loss of functional conformation. even "low" levels of H2O2 (from a bottle) can
overwhelm the cells enzymatic capacity to convert it to water and oxygen. btw as far as i know everything that rely on aerobic respiration has minute
concentrations of hydrogen peroxide as it is a product of oxidative phosphorylation.
as for that bombadier beetle, beats me :/
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