Magazine article Science News

Dam the Bacteria, Drugs and Vaccines Ahead

Magazine article Science News

Dam the Bacteria, Drugs and Vaccines Ahead

Article excerpt

Growing in a test tube, bacteria may appear harmless. When they infect a host, however, the microbes draw upon a concealed repertoire of molecular tools to dodge immune defenses and cause disease. Much like the famed Trojan horse, bacteria "hide their weapons until they're inside," notes Michael J. Mahan of the University of California, Santa Barbara.

In the May 7 SCIENCE, Mahan and his colleagues show that a protein called DNA adenine methylase, or Dam, regulates a bacterium's use of its armament. Without Dam, it's no longer virulent.

The findings suggest that Dam offers an appealing target for new antibiotics. Moreover, bacteria weakened by mutations in the gene for Dam might serve as vaccines against many diseases.

Like other methylases, Dam chemically coats DNA with clusters of atoms known as methyl groups. In doing so, it governs bacterial processes such as DNA replication and repair.

Mahan's group established the protein's role in virulence by disabling its gene in Salmonella typhimurium, which causes food poisoning in people and typhoid fever in mice. When researchers infected rodents with bacteria unable to make Dam, disease rarely resulted.

Mahan's team had previously identified around 250 genes activated in S. typhimurium when it infects a host. In the mutant bacteria, as many as 50 of these genes become active when the microbes are grown outside a host in test tubes. Dam seems to normally repress the genes until needed during an infection.

Unleashing the genes at the wrong time during an infection can prove troublesome to a bacterium. …

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