Thursday, February 18, 2016

KU Cryogenic Storage Expands with Biodiversity Collections

Andy Bentley removes specimens from a cryogenic dewar.


If you think you are cold this winter, remember others always have it worse. For instance, consider the tissue samples at the KU Biodiversity Institute.

The KU Biodiversity Institute stores thousands of tissue samples from species found around the globe at a frosty -175 degrees Celsius. The specimens are stored in dewars, which are large, vacuum-sealed containers with a pool of liquid nitrogen at the bottom. While -175 degrees is hard to imagine, the newest dewar at KU dips even lower.

“The latest one we’ve acquired runs at -190 degrees Celsius, but otherwise functions much in the same way,” said KU Ichthyology Collections Manager Andy Bentley.


To put that in perspective, NASA satellites found locations in east Antarctica reaching temperatures of -135.8 degrees Celsius, or -93.2 degrees Fahrenheit, still almost 60 degrees shy of the dewar’s temperatures. These antarctic locations boast the lowest temperatures found naturally on earth to date. Humans are expected to survive only three minutes in these frozen conditions--not nearly enough time to build a snowman.
East Antarctica, warmer than a cryogenic dewar.
The extreme temperatures in dewars preserve usable DNA in tissue samples taken from whole specimens. The voucher specimens are often stored in structure-preserving formaldehyde solutions. However, formaldehyde destroys a specimen’s DNA, rendering them useless for further genetic study. Researchers need a way to keep both the DNA and the whole specimen preserved.


“We need a way to preserve DNA before the specimens are fixed in formaldehyde,” Bentley said. “So now in the field we take fresh specimens and extract samples of either internal organs or muscle tissue, place them in a tube, and freeze them before sending the rest of the specimen to be preserved.”


Tissues preserved in the dewars are in constant demand. Researchers from all over the world review online catalogs of stored specimens and send requests for tissues that could further their research. Upon receiving a request, the specimen is carefully extracted from the dewar and thawed on ice. Once thawed, a tiny piece of tissue is sliced from the sample and shipped in ninety-five percent ethanol.


The number and variety of specimens available for research is growing rapidly. The two dewars currently used are quickly filling with tissue samples. Bentley expects the newest dewar to see use before 2017.


“There’s new material coming in from the field at a rate of ten percent a year,” Bentley said. “In ichthyology we expect another 1,100 tissues a year, so with that kind of growth across all departments we expect to fill the two current dewars in six to eight months.”


When the first two dewars near capacity, the third will be filled with eight-to-ten inches of liquid nitrogen. This level is monitored 24 hours a day to maintain the crucially cold temperatures. Once filled, the third dewar stands ready to support the growing collection.


“There is a fairly large portion of material that is unique to our collection,” Bentley said. “The ichthyology collection, we think, is probably one of the largest ichthyology tissue collections in the world, based on taxonomic and geographic scope.”