Genome Sequence Aids War on Tuberculosis

Article excerpt

Scientists often turn to military metaphors when they describe how the body tries to fend off infectious agents. Immune cells turn into valiant soldiers rallying to a noble cause, while bacteria and viruses become the merciless invading army to be defeated.

In that sense, microbiologists are best viewed as spies studying the enemy to determine its strengths and weaknesses. In the ongoing fight against the bacterium that causes tuberculosis, which claims more lives annually than any other infectious agent, these spies have now collected a long-awaited body of intelligence. In the June 11 Nature, they unveil the complete DNA sequence of the bacterium's more than 4,000 genes, laying bare all its potential weapons and defenses.

With such information, scientists hope to pinpoint novel targets for drugs. Moreover, by identifying bacterial molecules that trigger immune responses, they may find new leads to vaccines. "The sequence marks a new phase in the battle against one of mankind's most successful predators," writes Douglas B. Young of the Imperial College School of Medicine in London in a commentary accompanying the report on the Mycobacterium tuberculosis genome.

Scientists from the Pasteur Institute in Paris and the Sanger Centre in Hinxton, England, spearheaded the sequencing project. They found that the microbial genome consists of more than 4.4 million base pairs, the protein-encoding sub-units of DNA.

Unlike many bacteria, M. tuberculosis has a complex cell wall, and many of the newly identified genes play a role in creating this protective barrier. One unexpected finding is that the tuberculosis bacterium has more than 250 genes devoted to metabolizing lipid molecules. This suggests that the microbe may obtain much of its energy by digesting lipids of its host, says Stewart T. Cole of the Pasteur Institute.

The researchers have also identified a large number of genes that appear to encode proteins secreted or displayed on the surface of cells. …