Species Scanning(2)

Identifying species

iBOL is likely the most massive project of its kind following the human genome project. Over the years, taxonomists had been thinking of ways to quickly identify various species, said Zhang Yaping, head of Kunming Institute of Zoology of CAS.

With more and more plant and animal specimens brought to Europe from Asia, Africa and America, there is a desperate need for a simple and effective naming system.

Since scientists discovered the structure of DNA in the middle of the 20th century, taxonomy has also benefited from this biological revolution. In the 1980s, scientists compared the similarities and differences among birds and redefined the classification of tens of thousands of the species.

This achievement was furthered in the 1990s. As DNA sequencing technology continued to improve, the sequencing of more species had been created. Through comparing these data, scientists are now able to find answers to some long-held questions, such as the genetic relationship between chimpanzees and human beings.

When Hebert was browsing in a supermarket, the idea of a DNA barcode struck him. If consumers could get loads of information of a commodity by simply scanning the lines of a barcode, why couldn't a similar method be used to identify organisms on Earth?

Although determining the evolutionary relationship between different species through DNA was nothing new, Hebert nonetheless presented a breakthrough idea. He suggested differentiating various species by a specific DNA fragment instead of the whole genomic sequence. The challenge for scientists was to find these DNA fragments to better identify species. No matter which micro tissue the fragment came from, scientists could read the nucleic acid sequence using a handheld barcode reader.

The information would then be submitted to a reference database where scientists could retrieve the organism's name, a picture, a description and other information. Also, the database could be used to identify undiscovered species.

Finally, the position of the DNA fragment was determined. It was the - oxidase I gene (COI) from the mitochondria, which enjoys a mutation rate much higher than a nucleus' DNA and therefore serves as a "molecular clock" recording biological evolution. Hebert selected the DNA fragment with about 650 letters in the COI gene as the DNA barcode used to differentiate species.

"Judging from the world's current genetic testing technology, about 600 letters are optimal for effective detection," said Bai Fengyan, a researcher with the Institute of Microbiology of CAS, and also Deputy Director of the State Key Laboratory of Mycology. "If it's too long, then the detection is not reliable. And if it's too short, the detection might not be accurate."

The DNA barcode has some major advantages, said Chen Shilin, a researcher with the Institute of Medical Plant Development of Chinese Academy of Medical Sciences.

First of all, only one or few gene fragments are needed to accurately identify most species of a genus or family or even dozens of genera or families. Second, it is more efficient. A large number of species can be identified within a short time. Third, the process is easy to carry out. Fourth, it can detect the letters automatically and effectively. Finally, the Internet can be use to enhance data sharing.

Future used

An incident in 2010 at the Zhongshan Entry-Exit Inspection and Quarantine Bureau in Guangdong Province illustrated best the advantage of DNA barcode technology.

The inspection and quarantine personnel found a large number of fly pupas in waste paper which was brought into China. They believed the identification of the pupas could only be conducted after they became flies, which normally would have taken several weeks or longer if the pupas were dead.

To their surprise, the identification report was sent out five days later and identified the pupas as red-headed flies which were carriers of various infectious diseases such as cholera.

Because of this technology, the quarantine period was shortened by two to three weeks, which was previously unimaginable.

More than 50 of the world's 100 most threatened species announced by the International Union for Conservation of Nature were found in China in 2009, causing direct and indirect economic losses of up to 130 billion yuan ($20.59 billion) per year.

DNA barcode identification technology will likely continue to prove beneficial for inspection and quarantine purposes and to reduce the economic losses brought about by the invasion of poisonous insects.