Cold Facts was privileged to spend a morning with Dr. Shannon Hackett, the Richard and Jill Chaifetz Associate Curator, Head, Bird Division, Zoology Department, at Chicago’s Field Museum of Natural History. We wanted to learn more about the museum’s cryogenic storage facility and its role in the collections and research done by scientists at this world-famous institution. (View a photo gallery from our tour.)
We started out in Hackett’s office on the upper floors of the museum and wound up in the basement where the specimens are cryogenically stored. Our tour and conversations provided a thoroughly fascinating glimpse into what Hackett refers to as “The Tree of Life,” that is, the interconnected world of living organisms, and the important role cryogenics is playing in furthering research into its mysteries.
Hackett told us that the specimens that are ultimately stored beneath the museum come from all over the world. They are gathered as the result of field programs that are worldwide in scope and cut across almost all of the taxonomic diversity of life on earth, a feature that makes the collections special. In total, the museum’s collection represents more than 200,000 individual specimens.
In the Bird Division alone, Hackett, her husband Dr. John Bates (also Curator of Birds), and their staff work with almost 40,000 individual specimens and 80,000 small samples that are stored in the facility. The Mammal Division has roughly the same number, amounting to more than 150,000 birds and mammals together. Then there are plants, other animals, and DNA samples from the specimens they have in the collections as well.
Research at the Field Museum
The aim of Hackett’s research is to better understand the interconnectedness of life, a daunting task that is made somewhat easier thanks to the museum’s comprehensive collection—one she describes as the “gold standard”—which includes not only tissue samples, but original specimens, a luxury for researchers who can use both resources to further their studies.
“DNA reveals all kinds of information you would not have known by just looking at the sample,” said Hackett. “So if you find something different in the DNA, you need to go back to the individual and actually look to see if you find something different about the specimen—if it actually looks different.”
For Hackett and other museum researchers, maximizing the utility of the specimens, for research now and in the future, is a top priority.
“We will come and go and our theories as scientists will come and go… but the one thing I know for sure is that those specimens will still play the most prominent role in the science that goes on inside of this institution,” said Hackett, adding that some of their oldest specimens date back 150 years. “That’s the lasting legacy of the work that we do here.”
Methods of collection, too, have improved over time. While in the past, LN2 was not used in the field, some of their current studies involve taking LN2 dry shippers into the field for specimen collection.
And in keeping with their goal of maintaining utility, researchers are making use of improved imaging techniques that won’t destroy the specimens, allowing researchers to find clues they weren’t able to in the past.
“Now we have the ability to document the exact locality where specimens were collected,” said Hackett.
Armed with extensive resources, both physical and technological, Hackett and her team can study genetic diversity and changes over time. New computer technologies, new data and new analytical techniques contribute to their expanded view of genetic variability.
“Now we can sequence the whole genome using the specimens in our collection,” Hackett said. “These specimens are now at the forefront of new knowledge of biodiversity.”
So why is knowledge of biodiversity important to humans? Hackett says for her it all comes back to the interconnectedness of life on earth, also conceptualized as the “Tree of Life.”
“Researchers have evolutionary questions such as why don’t naked mole rats get cancer and why do sharks have such low rates of cancer? So we need to know what naked mole rats are related to and how their genomes might have changed compared to those of animals they are related to,” Hackett said. “When we answer these questions, we hope to use the information imbedded in those genomes to help humans.”
Bates, Hackett, their students, and others in the Bird Division do extensive field work. In fact, at the time of our visit, a group was just returning from Africa that afternoon. These researchers are studying parasites and pathogens that live in and on birds, looking for novel bacteria or viruses. An ongoing project that focuses on malaria keeps the researchers mindful of the connections between the disease in birds and in humans.
Hackett says they are gathering baseline data from which threats to human or environmental health can be compared.
“Humans ignore the rest of life on earth at their own peril, because there certainly are going to be solutions to problems we think of as uniquely affecting humans from other species,” said Hackett. “So exploiting in the best way the things that have happened in the evolutionary process is one of the reasons why museums can play such a strong role in things that are not thought of as typically museum-related.”Every department at the museum uses the cryogenically frozen samples, Hackett said. “Because we have all of the ‘life on earth’ kinds of disciplines, our collections are some of the most comprehensive in the world.”
While these samples are in safekeeping, what seems most difficult to protect these days are the researchers themselves. Financial problems at the museum have very recently led to major cuts in funding—down $5 million from a $60 million yearly operating budget. Since our interview, the anthropology, zoology, geology and botany departments have been merged. These departments will lose a total of 18 positions, including 6 of 27 curators.
Cuts like these could threaten an institution that the Chicago Tribune describes as one with a “demanding double mission: serving the public with relevant and engaging exhibits while supporting internationally recognized scientific research.” Like many other research institutions in the US, funding problems are an ever-present threat, as we in the cryogenics community know.
Classification and Preparation
Our tour started with the area where specimens are classified and prepared. Much of the work of cleaning the flesh off these tiny, delicate bones is done by Dermestid beetles, who feed on the flesh without damaging the fragile bones, a method that has proved much more effective than cleaning by human hands. Hackett remarked that when the specimens are soaked in alcohol in the field to preserve them for shipping to the museum, the beetles seem to do a better job of cleaning!
Many specimens are gathered through a salvage program that makes use of birds killed in the Chicagoland area after flying into windows.
Before they make their way to the museum’s larger cryogenic storage area, specimens are stored in a smaller ultra cold freezer housed in the preparation room.
DNA LabOn the way to the cryo storage area, we made a stop at the museum’s DNA lab, with a sleek, public-facing glass-walled area that lets curious museum visitors observe the work of scientists and participate in daily Q&A sessions. A DNA sequencer and other equipment are on display.
Because of the collection and the nature of their work, Hackett is often asked by museum guests about recreation of certain species, notably dinosaurs. Of course, the researchers must disappoint them. “It’s not cryonics, she said. “People want to know if we are going to bring the dinosaurs back to life. They don’t understand how much work it would take to turn even a genome sequence into a living being.”
For particularly difficult extractions of DNA, such as from plants and some insects, lab personnel call on a piece of equipment appropriately nicknamed “The Smashinator.” It uses stainless steel tubes with rods inside, filled with LN2, and shakes violently and loudly until the tissues turn into powder. This enables the breaking down of cells and cell walls, after which DNA extraction is much easier.
Collections Resource CenterTwo stories under the museum sits the main attraction for anyone interested in cryogenics: the Cryogenics Room inside the Collections Resource Center. Opened about six years ago, the facility has a large glass front window, allowing individuals to get a peek inside at the large tanks lining the left side of the room. We saw equipment from many of our CSA Corporate Sustaining Members throughout the lab.
Strict security measures, including limited access for individuals, ensure safety. There is also an alarm system to prevent any accidental exposure to too much LN2 and low oxygen levels.
The staff has modified the vessels in the lab to fit their needs. Steps have been added, accommodating shorter people, and they have also built special metal “arms” on the top doors of these vessels to facilitate opening and to keep them from slamming down.
The center’s method of storage previously involved ultra cold freezers with compressors, but staff found that they went out of service frequently and contributed to high electricity costs. Using nitrogen to cool has saved significant amounts of money for the museum and provides a more reliably cold environment.All the tissue in these vessels comes from the collections and is all catalogued in a database. To contain the samples, they use special internally threaded 2 milliliter Nunc cryogenic tubes—not glass, since glass is too fragile. These tubes can withstand the low temperatures without cracking as long as they are not overfilled.
We also got a look at the dry shippers that the researchers take into the field. Nitrogen is poured in and absorbed by the vessel’s lining. They cool it down and put the specimens they have gathered in it. When they’re ready to take the shipper on the plane, the LN2 is simply dumped out. It is well insulated and will hold cold temperatures for days.
There are 80,000 two-milliliter tubes stored in each of the lab’s four vessels, which cool the specimens in the vapor stage. Hackett explained that if a tube were to crack and the vessel cooled in liquid, the cracked tube could spill its contents onto all the other tubes. There’s a stainless steel platform on the bottom of the vessel, with the nitrogen below it. The vapor from the nitrogen keeps it at approximately -170˚ C.
A detector sensor signals when there is either too little nitrogen or too high a temperature and this automatically opens a solenoid so that nitrogen flows in under very low pressure. The vessels have temperature and level sensors. Every couple of weeks employees wheel the tanks out to the loading dock and they’re refilled with nitrogen from a special tanker truck called an Orca.
Other facilities in the museum that also use nitrogen include the scanning electron microscope lab and the elemental analysis lab in the anthropology department where they also use liquid argon and helium and other gases to study elements.
Our morning spent with Hackett was informative, enlightening and somewhat rare: the average museum visitor has no idea what goes on in the many rooms tucked far away from the public exhibits.
“There are [so many] people with PhDs on staff here, it’s like a university,” said Hackett. “We have people all over the world studying almost whatever you could think of and a whole bunch of things you’ve never heard of.”