Anthrax Genome is Decoded

WASHINGTON -- The complete genetic blueprint of Bacillus anthracis - the microbe that gained notoriety during the 2001 anthrax mail attacks - is now known, researchers announced April 30. A formidable bioterrorist threat and the cause of potentially fatal inhalational anthrax, B. anthracis differs very little from the common soil bacterium that is its near relative, the scientists discovered. Those genetic differences are enough to give B. anthracis its disease-causing properties and may also give scientists valuable clues to its vulnerabilities.

The team of researchers supported by the National Institute of Allergy and Infectious Diseases (NIAID) and other federal agencies was led by Claire M. Fraser, PhD, and Timothy Read, PhD, at The Institute of Genomic Research in Rockville, Md. The complete sequence of the 5.2 million base pairs of the DNA in B. anthracis' single chromosome is published in the May 1, 2003 issue of Nature.

"The pace of microbial genomics research continues to be rapid; B. anthracis is just the latest of dozens of important human pathogens to be sequenced," notes NIAID Director Anthony S. Fauci, MD. "As ever more precise details emerge about the genetic make-up of these organisms, our ability to design effective drugs and vaccines against the diseases they cause is greatly improved," he adds. To date, NIAID has supported sequencing efforts for more than 30 medically important microbes, many of which cause infectious diseases or are potential bioterror agents (see http://www.niaid.nih.gov/dmid/genomes).

Read and his colleagues compared an isolate of the Ames strain of B. anthracis with two closely related Bacillus bacteria. "There is remarkably little difference among these genomes," says Read. "In the 5,000 or more genes we analyzed, we found only 150 or so significant differences."

Read and his coworkers found a number of genes encoding proteins that B. anthracis may need to enter its host's cells. These could provide targets for drugs designed against the organism, says Read.

Unlike its near relatives, B. anthracis possesses genes that give it the ability to thrive on protein-rich matter such as the decaying animal bodies it frequently grows on, the scientists discovered. Their analysis also found that B. anthracis has an enhanced capacity to scavenge iron, which it may use to survive in its host.

Using techniques of comparative genomics, the investigators gleaned several clues about the possible evolutionary pathway taken by B. anthracis ancestors. The similarities between certain B. anthracis genes and those of microbes that infect insects, for example, suggest that a recent ancestor of B. anthracis may have infected insects. Of note is a similarity between one gene of Yersinia pestis, which causes plague in mammals and can also infect insects, and a gene in B. anthracis, which infects only mammals.

NIAID supported the anthrax sequencing through the pathogen functional genomics resource center at TIGR. This initiative, launched by NIAID in 2001, trains researchers in the latest techniques in functional genomics. It also serves as a reagent repository. The center's resources are available to the scientific community through online and other services. Besides NIAID, support for the anthrax sequencing effort came from the United States Office of Naval Research, the Department of Energy and the United Kingdom's Defense Sciences Technology Laboratory.

NIAID is a component of the National Institutes of Health (NIH), which is an agency of the Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, illness from potential agents of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma and allergies.

Reference: T Read et al. The genome sequence of Bacillus anthracis Ames and comparison to closely related bacteria. Nature. 423:82-86 (2003).

Source: National Institutes of Health