The Laboratory
in the News

Faster detection of salmonella
Biomedical scientists Peter Agron and Gary Andersen have developed a DNA-based detection system for identifying the presence of the salmonella pathogen, a major cause of food poisoning in humans. In a paper published in November 2001 in Applied & Environmental Microbiology, Agron and Andersen described their work to develop a DNA signature that will cut down the time usually taken to identify Salmonella enteritidis—the strain that causes bacterial infections—from as long as 2 weeks to as short as 2 hours.
During a year-long research effort, Agron and Andersen identified unique segments of DNA in S. enteritidis. They used a technique called suppression subtractive hybridization to compare the DNA of similar strains of Salmonella and determine what fragments of the DNA of enteritidis were unique and therefore the basis of its signature. Then they designed primers, or DNA markers, of the unique enteritidis regions. The primers were replicated many times using the polymerase chain reaction, and the replicated regions were processed to identify and characterize S. enteritidis unambiguously.
Coauthoring the journal article with Agron and Andersen were Jessica Wollard, also of Lawrence Livermore; Richard Walker, Sherilyn Sawyer, and Dawn Hayes of the California Animal Health and Food Safety Laboratory in Davis, California; and Hailu Kinde of the California Animal Health and Food Safety Laboratory in San Bernardino, California.
Contact: Peter Agron (925) 423-1284 (agron1@llnl.gov) or Gary Andersen (925) 423-2525 (andersen2@llnl.gov).

Need for explosives simulants increases
A California company with ties to the Laboratory predicts that its business will grow as a result of the September 11 attacks.
Van Aiken International, located outside Los Angeles, expects that the need to train more dogs to detect explosives and the increased screening of airline baggage for explosives will put a high demand on the explosives simulants that it is manufacturing under license from Lawrence Livermore.
Some 6 years ago, researchers at Livermore began developing high-explosive simulants, primarily to train bomb-sniffing dogs in real-life situations without posing a hazard. John Kury, project leader of the program, said that he and his team were trying to develop a full suite of simulants to match commercial explosives, gunpowders, and plastic explosives similar to those used to down the Pan Am flight over Lockerbie, Scotland.
Kury said that the simulant developed at the Laboratory contains just 8 percent of explosive, has passed all Department of Transportation tests, and is not classified
as hazardous. It can be detected by trained dogs, and it looks like an explosive to an
x-ray machine because it has the same density and average atomic number as real explosives.
Contact: John Kury (925) 422-6311.

Volcanic eruptions affected global temperature
Satellite measurements of temperature, which began to be collected in 1979, have shown little or no warming in the lower troposphere. These data have been cited to support skepticism of global warming. But recent research by atmospheric scientists has explained the apparent difference in warming rates at Earth’s surface and in its lower troposphere.
In a paper published in November 2001 in the Journal of Geophysical Research– Atmospheres, these scientists presented their discovery that large volcanic eruptions cooled Earth’s lower troposphere more than the surface and likely masked the actual warming of the troposphere..
The conclusion is presented in “Accounting for the Effects of Volcanoes and ENSO in Comparisons of Modeled and Observed Temperature Trends.” The work was performed by Laboratory researchers Benjamin Santer, Charles Doutriaux, James Boyle, Sailes Sengupta, and Karl Taylor, who teamed with scientists from the National Center for Atmosphere Research; National Aeronautics and Space Administration/Goddard Institute for Space Studies; the Climatic Research Unit at the University of East Anglia, United Kingdom; and the Max Planck Institute for Meteorology, Germany.
The scientists used a statistical procedure to quantify
the volcanic influences on surface and tropospheric temperatures. To do so, they also had to separate out the effects of El Niño events, which coincided with both of the eruptions they were studying—El Chichón in Mexico in 1982 and Mount Pinatubo in the Philippines in 1991.
“Our recent work shows that some of the differences between warming rates at the Earth’s surface and in the lower troposphere are due to the effects of volcanic eruptions and stratospheric ozone depletion,” said Santer, the lead author. “Both of these factors probably cooled the lower troposphere by more than the surface, for physical reasons that are well understood. Without ozone depletion and the recent eruptions of El Chichón and Pinatubo, it is highly likely that the lower troposphere would have warmed over the last two decades.” These conclusions were reinforced by results from numerical models of the climate system.
Contact: Benjamin Santer (santer1@llnl.gov).