By TANG YUANKAI

THERE are children who can spend many contented hours watching lines of industrious ants go back and forth on their urgent mission of collecting food. Some scientists, however, make these children's fascination seem insignificant, and spend years studying ants as part of their research. Among them is Dr. Zhang Guojie at Shenzhen BGI, China's largest genome and bioinformatics analysis center, where he is associate director of its Science Department and head of its Genomic Evolution and Comparison Center.

Dr. Zhang started sequencing ants' genomes in 2009. His work is a part of the 1,000 Plant and Animal Reference Genomes Project launched by BGI. In September 2011, Zhang resumed his cooperation with researchers at the University of Copenhagen to study the genome of leaf-cutting ants.

Good Farmers

Ants are among the four animals, the others being termites, bark beetles and mankind, that are known to have farming abilities. Ants have been farming much longer than humans. They used techniques such as fertilizing and weeding some 50 million years ago to cultivate their favorite food – fungi.

Dr. Zhang, along with other scientists from China and various institutions in Denmark and Switzerland, published their analysis of sequencing the genome of the leaf-cutting ant Acromyrmex echinatior, in the journal Genome Research. "The research that we have carried out with the University of Copenhagen has set an important foundation for genetics in social behavioral studies, providing more information and knowledge about leaf-cutting ants," said Dr. Zhang.

Leaf-cutting ants mainly inhabit in South America, Central America and the southern part of the United States. They are taken as an archetype for ants with an agricultural bent. There are a number of physiological and behavioral differences between these and other species of ants. In comparing the Acromyrmex echinatior genome to those of other ant species, the scientists were able to analyze genetic changes that were likely to have accompanied this species' evolution.

"Leaf-cutting ants process food in an interesting way," Zhang explained. "First, they cut leaves into tiny pieces and then chew them into a paste. That is used as a surface to grow fungi consumed by ants in the colony."

Leaf-cutting ants are also unique among ants in terms of their method of reproduction. While the queens of most ant species mate with only one male ant once in their lives, a leaf-cutting queen mates with many males and stores all the sperms that she will need to fertilize the eggs she produces over decades. Researchers believe this mating habit probably results from the expansion of a certain gene family in the leaf-cutting ant genome.

The Secret to Long Life

Within a colony and throughout the ant family, ants can be of vastly different sizes, and also differ greatly in terms of longevity and behavior. For example, the queen can live for nearly ten years while worker ants may live for just one to two months. "We hope to find the reasons for these differences by analyzing ants' genomes," Dr. Zhang said.

The Shenzhen BGI has cooperated with the School of Medicine at New York University, Arizona State University and the School of Medicine at the University of Pennsylvania on the study of the genomes of two other ant species – Camponotus floridanus and Harpegnathos saltator. These two species are different not only in behaviors and ways of predation, but also in social structures and divisions of labor. Furthermore, in an organized ant society, the queen ant has a much longer lifespan – ten times that of the offspring of worker ants and 500 times that of male ants.

In comparing the genomes of Camponotus floridanus and Harpegnathos saltator, as well as their gene expressions at different life phases and social divisions, scientists have discovered genes related to ants' aging process, nerve functions and chemical communications. "These results have offered us a good model for further study on behaviors and longevity control in human beings," Zhang said. "Analyzing ants' genomes is a key to finding out how genetics influences the aging process and social behaviors of humans."

Solution to Antibiotics Resistance

Ants are also notable for their outstanding ability to manage potentially health-threatening waste. The methods they employ in waste management include using antibiotics produced by microorganisms to prevent the spread of pernicious bacteria and diseases.

Ants began using antibiotics much earlier than human beings, as long ago as 50 million years. But this begs the questions of why no resistance has developed in ants and why antibiotics are still effective in them after such a long period of time. Antibiotics are already less effective in treating human diseases because strains of bacteria in the human body become resistant to them due to their improper use. Researchers in this area are developing new antibiotics or finding ways to regenerate existing antibiotics. Some scientists have turned to ants for solutions, to determine whether or not they have evolved a solution to the "antibiotics issue."