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Electric Shock of Bacteria
Name: James
Status: Other
Age: 50s
Location: N/A
Country: N/A
Date: N/A
Question:
Question is what is the minimal(threshold) type
of current necessary to kill bacteria? AC or DC?, voltage?, were the
microorganisms in solution of
some sort, etc.
Any and all info would be helpful.
Replies:
Dear Mr. Gross,
My experience with electrical shock and bacteria is
limited to the application of 'electroporation' (also
called electro-transformation), a method to force DNA
into bacteria. The bacteria are suspended in a
solution of glycerol and glucose (isotonic so that the
bacteria won't burst as they do in water, and free of
ions to give sufficient resistance). This solution is
put in a cuvette sided with two electrodes and DNA is
added. An electrical current is applied for several
milisec, and the result is that the DNA is 'shot' into
the bacterial cells.
The voltage should be high enough
to be effective, but not too high so that the bacteria
survive. When salts (from the growth medium) are not
sufficiently removed, the voltage results in a current
(a flash!) and the bacteria are killed. I am not sure
weather it is the heat or the current itself (or the
combination) that kills the bugs. How much current is
needed for electroporation, and how much the bacteria
can survive, is dependent on the organism. Note,
however, that these experiments are optimalized for
cell survival, not for killing. I did a quick search
for you on the internet about applications:
Research is going on to use electrical current to kill
micro-organisms, see for instance this (lay-man)
article on killing bacteria and viruses in medical
blood products
(http://www.ioa.com/~dragonfly/blackbox.html).
Bacteria that form biofilms (multiple layers of
tightly packed cells) on catheders are a serious
problem in invasive medicine. Such bacteria are hard
to treat with antibiotics because the inner layers are
not reached. The application of electrical current
(1-10 mA/cm2), often in combination with antibiotics
is used for desinfection of such devises. See for
instance this scientific publication
(http://aac.asm.org/cgi/reprint/40/9/2012?view=reprint&pmid=8878572).
Another application to kill bacteria with help of
electricity is to rinse foods/cutting boards etc. with
electrolyzed water
(see
http://www.scienceagogo.com/news/20000728182516data_trunc_sys.shtml).
In this case it is the acidity of the water and
oxidation/reduction that distroy the microorganisms.
I hope this answers your questions
Trudy Wassenaar
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Update: June 2012
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