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CDC
Anthrax page
National Human
Genome Research Institute
Genetics researchers report they've completed sequencing the genome of anthrax.
As this ScienCentral News video reports, scientists can now zero in on what
makes anthrax a killer.
Bad Bug
Scientists at The Institute
for Genomic Research (TIGR) have finished sequencing the genome of the
bacterium that causes anthrax, and they say the killer bug is closely related
to a mostly harmless soil bacterium found in any garden.
Researchers report in the May 1, 2003 issue of the journal Nature
that there are only small differences between Bacillus anthracis, the
deadly anthrax bacterium, and Bacillus cereus, a common soil bacterium
that sometimes causes a form of food poisoning. “If you take the chromosome
of anthrax, you find, say, about 5000 genes,” explains Timothy
Read, assistant investigator at TIGR. “If you look at the similar
chromosomes of B. cereus, the garden strain, you'll find about 95 percent
the same genes. So it's very, very close, and mostly in the same order, in
the same place around the chromosome.”
But there is one key difference between these two strains of bacteria. “Basically,
the difference between B. anthracis and the closely-related soil strains
that are mostly pretty harmless is the fact that B. anthracis has two
of these extra circular [DNA] molecules in its genome called plasmids,”
says Read. “One of the plasmids contains genes that make the anthrax
a lethal toxin and the other plasmid makes the capsule that enables the bacterium
to escape from our immune system.” In other words, these plasmids carry
the key genes for anthrax’ toxicity and virulence—they make anthrax
a killer bug.
Researchers started sequencing the genome of B.
anthracis in 1998. (After the bioterror attacks in 2001, they confirmed
that the strain of anthrax used in the attacks, called the Ames strain, was
nearly identical to the one they sequenced. But this research will probably
not help authorities track down the source of the deadly anthrax used in 2001
that led to five deaths and 17 injuries.) TIGR is currently sequencing the
genomes of 14 strains of anthrax to be able to identify quickly the origins
of any new bioterror attacks. So far they have sequenced six of those 14.
“There will be some differences between different isolates and strains,”
explains Read. “But more and more, we'll actually begin to find out
what those genetic differences are. This B. anthracis genome sequence
can be used as sort of the basic blueprint for understanding the biology of
all B. anthracis.”
New Treatments
image: NBC News
Sequencing the anthrax genome will help scientists develop new drugs and vaccines
against the deadly bacterium. “The genome sequence, which actually we've
been making available since 1999, has already led to the next phase of anthrax
research, which is using the genome sequence and predicted genes to go in
and do experiments to fully understand the biology,” says Read. “For
instance, the genome sequence has enabled us to predict a lot of the proteins
that might be on the surface of anthrax. You can actually take these proteins
and see if these make good targets for vaccines and drugs. People have actually
been doing that for a while now. Shortly, we'll start to get some viable drugs
and vaccine targets from the genome sequence.”
The project was supported by the U.S.
Office of Naval Research, the National
Institute of Allergy and Infectious Diseases, the Department
of Energy, and the United Kingdom’s Defense
Sciences Technology Laboratory.
