Understanding the genetic structure of a bacterium will help in the development of an effective vaccine
Tamara Traubman
Biologists have succeeded in deciphering the genome of the bacterium that causes this disease. During human history, the bacterium - named Yersinia pestis - caused several worldwide epidemics and the death of 200 million people. The disease is still found in several regions of the world, including the western United States, but not in Israel.
The genome is the complete DNA of the organism; DNA is a long chain of chemical units in which the genetic information of organisms is encoded. Decoding a genome means that the researchers were able to identify the sequence of DNA units, in this case of a bacterium.
The scientists believe that deciphering the genome will help in the development of improved vaccines against the bacteria. This bacterium is also mentioned as a means that may be used in biological warfare, because it can be contracted by inhaling it from the air.
Decoding the genome can help, for example, in the development of a vaccine that is based on disrupting the work of the genes responsible for creating the bacterial envelope. The current vaccine against this disease is in limited use, because it has many side effects. The standard treatment is antibiotics, but this is only effective if the disease is in an early stage. In Africa, the bacterium has developed resistance to antibiotics.
The bacterium usually lives in rats, and spreads from rat to rat through fleas. Humans can contract it by being bitten by an infected flea, or by inhaling it from the air. In the most common case, the bacteria reaches the lymph nodes and causes swelling. In more rare and fatal cases it causes blood infection or lung inflammation.
New research has revealed that the bacterium became deadly about 1,500 years ago. Until then it was a bacterium that caused infections in the digestive system. "During the decoding of the genome, we discovered that within a short period of time the ancient bacterium acquired a large set of genes from another bacterium, including some genes that caused it to become a killer that wreaked havoc on the world," said the head of the decoding project, biologist Dr. Julian Parkhill, in a telephone interview from his office at the Sanger Center in Great Britain.
The first recorded epidemic took place between 546-542 AD, and was called the "Justinian Plague". It struck Asia, Africa and Europe, and according to various estimates caused the death of about 100 million people.
After that came the most famous plague of all, the "Black Plague", which destroyed about a third of the European population in the 14th century. The current outbreak began at the end of the 19th century (first cases were discovered in southern China in 1894). According to the World Health Organization, at least 3,000 people get sick every year.
The researchers published their findings in the scientific journal "Nature" and the decoding data also appears on the "Gene Bank", a website that contains DNA data of organisms (including humans) whose genomes have been decoded.
In the past, some experts expressed concern that publishing the genomes of deadly bacteria would aid in the development of biological weapons. But in an official announcement published by the Sanger Center, one of the partners in the study, Dr. Rick Tiball from the Proton Down Laboratory of the British Ministry of Defense, said that "the benefit of making the information available to the general public far outweighs the risk of someone obtaining it and using it for bad purposes."
According to Tibul, the information accumulated since the decoding work began about three years ago, has already helped him and his colleagues develop a new vaccine. According to him, the vaccine was found to be effective in animals and safe for use in humans as well.
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