Freeze-Drying Is Key to Saving Fungal Collection

Imagine. The scientists worked for months on an experiment, and then it happened: The fungal species that was critical to the entire experiment was accidently cross-contaminated. The researchers had been working on harvesting a gene that produces a key enzyme from a very special fungus. “No problem,” says taxonomist Maren Klich. She has pure inventory of exactly the fungal species needed to regroup. Experiment saved.

This is the kind of taxonomical rescue Klich conducts. She has been curator for nearly 30 years of the ARS Southern Regional Research Center’s (SRRC) 1,700 strains that make up the Fungal Culture Collection.

The collection is critical to the day-to-day work of career scientists who work at SRRC and beyond. Interestingly, Klich chose a method of preserving the collection that is essentially “the closest thing to putting microbes into suspended animation,” she says.

She and colleagues actually freeze-dry tiny amounts of a fungal species. In a small vacuum tube, water is removed from the frozen fungi. That suspends the life of the live organism. Fungi can stay in that condition for 50 years or more. “You end up with white pellets that can be resuspended,” says Klich. “We immerse the pellet in a liquid, and place the suspension on a petri dish containing agar, and the mold grows right out—it comes back to life.”

Another way the team could have chosen to preserve their live fungi was to freeze them in liquid nitrogen. “But if we had gone that route, we would have lost the entire collection during Hurricane Katrina,” says Klich.

After Katrina, evacuee scientists were barred from returning to SRRC, so they would not have been able to keep cultures frozen. “You have to replenish the liquid nitrogen, and we just could not do that after Katrina,” she says.

But when Klich was allowed to return, she found the collection safe and sound. She then turned her attention to helping other agencies identify potentially dangerous mold species that could occur as a result of water damage from the storm.—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.

Maren A. Klich is with the USDA-ARS Food and Feed Safety Laboratory, 1100 Robert. E. Lee Blvd., Bldg. 001, New Orleans, LA 70124; (504) 286-4361.

"Freeze-Drying Is Key to Saving Fungal Collection" was published in the January 2010 issue of Agricultural Research magazine.