How to wake up dormant microbial strains

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????The image shows a microbial strain bank. At present, the China General Microbiological Culture Collection Center preserves 11,977 patented strains, ranking 2nd in the world. (Image source: Science and Technology Daily)

An ancient strain that had been dormant for 20 years at the China General Microbiological Culture Collection Center recently became popular because of the Han Chunyu incident. This strain, called Natronobacterium gregoryi, became famous after being used by Han Chunyu, associate professor at Hebei University of Science and Technology, to achieve the genome editing technology NgAgo-gDNA.

The "China Microbial Resource Development Report 2016" released recently shows that culture collections around the world hold a total of 96,907 biological materials used for patent procedures, of which the China General Microbiological Culture Collection Center preserves 11,977 patented strains, ranking 2nd in the world.

On September 14, reporters entered the China General Microbiological Culture Collection Center (referred to as the Collection Center) to explore the daily life of microbial strains.

?A "life" bank supporting the future

Xin Yuhua, senior engineer at the China General Microbiological Culture Collection Center, said that Natronobacterium gregoryi was exchanged to China from Scotland 20 years ago by researcher Zhou Peijin, former director of the Institute of Microbiology, Chinese Academy of Sciences, and was first isolated from Lake Magadi in Kenya. As one of more than 5,000 kinds of microorganisms in the Collection Center, Natronobacterium gregoryi is in a dormant state either through vacuum freeze-drying or through liquid nitrogen ultra-low temperature freezing at about -190°C.

Some strains have even slept in cold storage for more than half a century. "Once there is a demand, they will be awakened and put into application," Xin Yuhua said. But today, humans still do not know how to culture 99% of the microorganisms on Earth. Only after culturing them can we know what they can do in the future and ultimately realize their use.

"The strains we select generally must have potential application value and rich biodiversity. Now, more and more microorganisms are being 'awakened' and showing their abilities in various fields," Xin Yuhua said. The microorganisms preserved by the culture collection center have been accumulated over the long term and continuously by several generations. Only time can reflect the value of preserving microbial resources. In addition, microbial resources bear on the future of biotechnology innovation.

It is worth noting that in May this year, the United States announced the launch of the "National Microbiome Initiative." The U.S. government will invest 121 million USD over the next two years as startup funding, and dozens of universities and research institutions will invest 400 million USD in the coming years.

Strain preservation has double "insurance"

As a national-level collection center in China that can simultaneously provide general strain resource services and preserve patented biological materials, the Collection Center was listed as an "International Depositary Authority under the Budapest Treaty" in 1995, becoming a microbial "bank" holding an international license.

"Here we mainly collect, preserve, identify, exchange and supply various biological materials," Xin Yuhua told the Science and Technology Daily reporter. Some strains isolated during research and development, whose functions are not yet known, are stored as resource reserves; and fungi that need to be collected and screened for research projects can also be stored as backups after the project is completed. Over several decades, the Collection Center has provided hundreds of thousands of strains of various microorganisms, making outstanding contributions to life science and biotechnology research and development in China.

Entering the underground Collection Center, the air was filled with a trace of chill, in sharp contrast to the muggy heat outside. In this liquid nitrogen biological storage tank room of about 100-plus sq m, about 30 "large tanks" with a capacity of 750 liters are placed, and 53,000 microbial strains such as bacteria, fungi and yeasts are hidden within them.

"Almost all strains are stored in liquid nitrogen. Biological materials are first preserved and 'backed up' here." Xin Yuhua lifted the lid of a liquid nitrogen tank, and steaming nitrogen rushed toward them. The reporter instinctively stepped back. Through the swirling mist, various microbial strains were "sleeping" in small iron boxes.

"The temperature in the liquid nitrogen tanks is maintained at about -190°C, and strains can be preserved here for decades," Xin Yuhua said, pointing to the ceiling. When the liquid nitrogen decreases, the "giant" liquid nitrogen tank upstairs will automatically sense it and replenish it in time. These expensive "refrigerants" are shipped directly from Tianjin.

Arriving at the low-temperature cold storage room was like entering a bank vault. Row after row of stainless steel cabinets reached up to the ceiling, and each cabinet was neatly arranged with many compartments like "drawers." Pull out a "drawer," and one could see many small vacuum glass tubes storing strains with different numbers. The test tubes contained a light yellow, already dried protective agent, and hidden within it were "dormant" microorganisms. This preservation method is called vacuum freeze-drying.

For strains preserved through double "insurance," the price of one strain is only 500-1,000 yuan. As a public welfare institution, the Collection Center's prices are not expensive and its quality is guaranteed. It is worth noting that new microbial species must be verified and preserved by the Collection Center before they can be validly published in international journals, and this is precisely the authority held by the China General Microbiological Culture Collection Center.