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| Strain Deposits and Accessions |
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Microorganisms may be accepted into the open or public
portion of the ARS Culture Collection. Strains to
be deposited in the ARS Culture Open Collection must
be accompanied by a completed and signed deposit form,
available here
[PDF, 58kb]. Please note that this now
a saveable PDF that can be completed using a PDF reader.
Please contact the Collection Manager, Mr.
James Swezey (e-mail:
james.swezey@ars.usda.gov) prior to sending your
strains to determine if they can be accepted into
the collection. Strains
will not be accepted into the collection without prior
approval.
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The majority
of strains maintained in the ARS Culture Collection
are kept as lyophilized (freeze-dried) preparations.
Culture ampules in refrigerated storage are seen in
the photo below on the left.
The first
large-scale use of lyophilization for culture preservation
was pioneered at NCAUR by Wickerham for yeasts and
by Raper for aspergilli and penicillia. The process
consists of freezing microorganisms within small glass
ampules in an appropriate liquid suspending medium
such as bovine serum and applying a vacuum to sublime
the water from the frozen preparations. Following
drying, the ampules are sealed under vacuum with a
gas-oxygen torch and then stored at 5ºC. This
process can be seen below on the right.
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Some
microorganisms, such as asporogenous filamentous fungi
and certain yeasts and bacteria, do not survive the
lyophilization process. These strains are maintained
as frozen stocks in liquid nitrogen. Liquid nitrogen
storage seems to
cause little or no genetic change in cells. The reasons
for not relying on this method exclusively for preservation
of cultures are: cost and the fact that lyophilized
preparations may be shipped by regular mail whereas
strains preserved by liquid nitrogen must first be grown
on agar
or in liquid medium to avoid the expense of shipping
frozen materials. |
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