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The Laboratory
in the News

Anthrax virulence depends on the strain
Different strains of the bacterium that causes anthrax vary in their virulence, and scientists are beginning to understand why. Six scientists from Lawrence Livermore, Louisiana State University (LSU), and the U.S. Army Medical Research Institute of Infectious Diseases published findings in the Journal of Clinical Microbiology that could lead to more effective vaccines against anthrax and better tools for tracking the source of anthrax attacks. The paper’s lead author was Pamala R. Coker, formerly of LSU and now at Livermore.
The anthrax genome has one large chromosome and two small pieces of DNA known as plasmids. The anthrax bacterium can contain not just one set of plasmids but could have as many as 243 copies of one plasmid and up to 32 copies of the other. That other plasmid, known as pX02, is more capable of causing disease when more copies of it are in a bacterial strain. In tests, the scientists found that an anthrax strain with just one pX02 plasmid killed 25 percent of the test animals, whereas a strain with 32 copies of the plasmid killed all the animals.
Scientists suspect the pX02 plasmid carries genes that allow the anthrax bacterium to develop an outer protein coat, and this coat shields it from the immune system. The more pX02 copies, the thicker that coating, and the more the anthrax bacterium can do its harm.
Coker says the discovery may help forensics scientists track down the country or laboratory that is the source of an anthrax strain used as a biological weapon. The plasmid technique could reveal genetic distinctions among varieties of anthrax, and that information could be used to match an attack germ with its terrorist perpetrator. She acknowledges that the research could also help others engineer more deadly forms of anthrax. Therefore, the federal government has urged scientists to carefully screen their work to prevent possible harm to national security. Livermore put the scientific paper through a careful security review before submitting it for publication.
Contact: Pamala Coker (925) 423-2817 (coker4@llnl.gov).

Coming soon: more detection technologies
Scientists in Livermore’s newly created Radiation Detection Center are investigating the application of more than a dozen advanced technologies to detect clandestine nuclear materials or nuclear devices. Many of the technologies were originally developed to search for black holes and supernovas in space. Now, these technologies contribute to fighting terrorism.
For example, Ultra-Spec is an ultrahigh resolution gamma-ray spectrometer that uses a detector at low temperatures to precisely measure gamma rays from nuclear materials. It records the warming caused by a single gamma ray hitting the detector’s superconducting material (usually tin). The temperature increase is measured to a precision within 0.1 percent. Ultra-Spec users will be able to distinguish emissions from different types of radioactive materials, thereby allowing easier identification of the exact makeup of the materials.
Another example is the Gamma-Ray Imaging Spectrometer, one of five gamma-ray imaging systems under development. It permits large-area pictures to be taken of radioactivity emissions to determine the presence and location of radioactive materials. The gamma-ray camera consists of many gamma-ray sensors working together to take pictures, acting like a digital camera for gamma rays. The spectrometer is the size of a large-screen television and will provide a tenfold increase in sensitivity for detecting nuclear materials or devices.
Contact: Simon Labov (925) 423-3818 (labov1@llnl.gov).



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UCRL-52000-03-7/8 | July 18, 2003