In article <1994Sep29.135409.14710 at es.dupont.com>, mccardaj at esvx23.es.dupont.com writes:
>> Main point from previous article:
>>>>I am doing some work using high pressure with ambient temperature for sterilizatliz
>>>ation purposes. Does anyone know how high pressure kills bacteria?
>>>>>>My original thought was that the water within t
>>>I would appreciate any discussion on the mechanism and of course if
>>>anyone has any good references/review articles to suggest I would be
>>>>>>Thanks,
>>>A.J. McCardell
>>>>>>I am not familiar to high pressure sterilization, and I find it
>>as a strange way of doing it. Bacteria is found at deep depths
>>of the ocean so I recon they may survive 4-500 atm. Water is not
>>a medium that will compress much. Think I read somewere (to long
>>ago so I can't give a reference) that bacteria live as usual when
>>you put pressure on them. I have also experinced that a "french
>>press" not were enough to kill a culture of cyanobacteria.
>>><snip snip>
> Please could someone explain to me what a "french press" is? This is the
> second reference to it and I have no idea what this is.
>A french pressure cell (and I have one sitting right next to me) is an ugly
machine. You put a suspension of your bacteria in a kind of armor plated
syringe with a plunger at the top and a narrow opening at the bottom (actually,
out the side just at the bottom). You the apply *LOTS* of pressure onto the
plunger - around 16,000 psi is common I believe. The cells get forced out of
the narrow opening, and lyse due to the pressure differential...
>> I like your idea about the most crucial step being the drop in pressure.
...Making the above comment correct. The actual physics invovled...hmmm. Got
me there!
Even with E. coli, however, one passage through the press is usually not
sufficient to lyse all the cells. Two or three passes are common, and this is
just to get optimum yield of protein...most people don't use these things to
sterilize stuff.
>> Yes, dead cells can be turbid too, but not lysed ones? My point was that I
> was expecting the cell to be lysed and therefore the suspension clear.
>
Lysed cells can be turbid - eg when making phage stocks of the lytic P1 virus,
you can tell the stage of lysis by holding the culture up to the light and
seeing big chunks of debris floating around.
> We have had a fair amount of success to date with everything but those nasty sp
> spores, specifically Bacillus stearothermophilus.
>Spores are meant to be hard to kill, aren't they?
> I am still hoping to generate more discussion on how high pressure affects the
> bacteria. By what mechanism(s) does it actually kill cells?
>Well, theres my tuppence worth.
Richard Heath
Department of Biochemistry
St Jude Children's Hospital,
Memphis, TN
