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USDA Agricultural Research Service
Foodborne Staph Toxin Pinpointed by New Assay
Mon, 14 Dec 2009 08:56:00 -0500
A new test that ARS researchers have developed to trace a Staphylococcus aureus toxin is one billion times more sensitive than the current "gold standard" assay. Click the image for more information about it. Botulism assay quickly detects potent foodborne toxin Arcobacter: Foodborne pathogen's genome exposed Garden microbe foils E. coli O157:H7 in laboratory tests Foodborne Staph Toxin Pinpointed by New Assay By Marcia Wood December 14, 2009 Most people need about two days to recover from being sickened by foods contaminated with what's known as staphylococcal enterotoxin A, or "SEA." Produced by Staphylococcus aureus bacteria, this toxin is a leading cause of foodborne illness in the United States and worldwide, according to Agricultural Research Service (ARS) research chemist Reuven Rasooly. To help public health officials trace the source of food poisoning outbreaks in which staph A is a suspect, and to give food makers another way to ensure the safety of their products, Rasooly has developed a superior new test for finding this toxin in foods. He and technician Paula M. Do developed the test at the ARS Western Regional Research Center in Albany, Calif. The ARS test can detect the toxin at levels that are a remarkable one billion times lower than the current "gold standard" assay for SEA. The researchers' experiments with chicken, beef and milk indicate that the assay reliably distinguishes active from inactive toxin and yields reproducible results. The test takes advantage of the fact that the toxin has a double life. Besides causing nausea, vomiting, diarrhea, and other gastroenteritis symptoms, SEA also acts as a superantigen—a molecule that activates large numbers of immune-system cells. The assay neatly exploits this trait by measuring proliferation of splenocytes, which are immune system cells produced in the spleen. For the assay, the cells are kept alive in laboratory petri dishes. The SEA assay is practical, comparatively fast, and relatively inexpensive. Experienced technicians can quickly learn how to perform the test using equipment that's standard in laboratories across the nation. Rasooly and Do describe their test in an article published earlier this year in FEMS Immunology and Medical Microbiology . ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture (USDA). The Albany research is one of dozens of studies conducted by agency scientists nationwide to help keep food safe—a top priority of the USDA.
Watermelon: Fruit on the Fast Track
Fri, 11 Dec 2009 06:55:00 -0500
ARS scientists Pat Wechter (left) and Amnon Levi have identified and characterized key genes regulating growth and development that enable watermelons to grow from tiny flowers to plus-size, market-ready produce in only five weeks. Click the image for more information about it. Researchers identify cause of watermelon vine decline Watermelon serves up medically important amino acid Watermelon line may help breeders combat mildew Watermelon: Fruit on the Fast Track By Ann Perry December 11, 2009 Agricultural Research Service (ARS) scientists are studying how watermelons grow from tiny flowers to plus-size, market-ready produce in only five weeks. Their findings have resulted in the first reported large-scale study that identified and characterized key genes regulating watermelon growth and development. The researchers included plant geneticist Amnon Levi and plant pathologist Pat Wechter at the ARS U.S. Vegetable Laboratory in Charleston, S.C. Plant geneticist Karen Harris at the ARS Crop Genetics and Breeding Research Unit in Tifton, Ga., plant geneticist Angela Davis at the ARS South Central Agricultural Research Laboratory in Lane, Okla., and molecular biologist Jim Giovannoni at the ARS Robert W. Holley Center for Agriculture and Health in Ithaca, N.Y., also contributed to the research. Tissue was taken from watermelons at three distinct stages during growth and ripening. Then the team analyzed RNA from all the tissue samples and used the RNA to develop a library of genes called expressed sequence tags (ESTs), which are unique gene segments involved in different aspects of development and metabolism. The researchers found that these genes were active in metabolism, cell growth, cell development, and transporting nutrients and other substances across cell walls. The genes also came into play in cell division, cellular communication, DNA copying, plant defense and stress response. The scientists also found a large number of ESTs that appear to be modulated in the fruit during development and ripening. But they can't match them up with any other known plant ESTs, so they may be unique to watermelon. This information could benefit plant breeders and watermelon producers alike. Since cultivated watermelons are not genetically diverse, they are more vulnerable to pathogens and environmental stresses. So finding sources of genetic resistance to watermelon diseases is essential to the continued success of U.S. production. Results from this study were published in Biomed Central Genomics. Read more about this research in the November/December 2009 issue of Agricultural Research magazine. ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture (USDA). This research supports the USDA priority of promoting international food security.
ARS Scientists Help Fight Damaging Moth in Africa
Thu, 10 Dec 2009 09:12:00 -0500
ARS is working on ways to keep the false coddling moth out of the U.S. with the aim of averting a threat to the country's citrus, corn, cotton and a wide range of nuts and fruits. Photo courtesy of the Pest and Diseases Image Library, Bugwood.org Scientists pit fungus against apple pest New pheromone sprayer leads amorous moths astray To catch a pest, scientists fine tune traps ARS Scientists Help Fight Damaging Moth in Africa By Dennis O'Brien December 10, 2009 Agricultural Research Service (ARS) scientists have launched a preemptive strike to combat the false codling moth, a major pest in its native Africa. If the moth enters the United States, it will damage citrus, corn, cotton and a wide range of nuts and fruits, according to entomologist James Carpenter, at the ARS Crop Protection and Management Research Unit in Tifton, Ga. He is working to control the moth in Africa, thereby reducing the risk of its arrival in the United States—and ensuring a future weapon if it does show up. Carpenter and an international team of scientists have turned to a tried-and-true method of pest control: the sterile insect technique (SIT). Using this technique, both male and female insects are irradiated. The female insects are left sterile by the irradiation and are unable to produce offspring. The males are completely or partially sterilized; if they are able to produce offspring, the offspring are sterile. By repeating the process, the target insect population eventually declines. Originally developed by ARS scientists to control screwworms, SIT is now used to control Mediterranean fruit flies, pink bollworms and a number of other moths and pests. Carpenter began working with South African scientists several years ago to develop SIT to control false codling moths and to test the methods in South Africa’s citrus groves. In a series of studies, Carpenter and his colleagues found that irradiating adult false codling moths sterilized the females and ensured that males produced only sterile offspring. The research has been largely funded by the Food and Agriculture Organization of the United Nations and the International Atomic Energy Agency, which is dedicated to finding peaceful uses for nuclear energy. Carpenter also helped South African scientists establish a facility in a rural village where codling moths are reared, chilled, irradiated and transported for release in the orchards. In a year of operations, sterilized moths released aerially and by hand drastically reduced moth populations in South Africa’s Western Cape region. The sterile moths also are available for shipment to the United States if they are needed here. A report on this work was recently published in Area-Wide Control of Insect Pests. ARS is the principal scientific research agency of the U.S. Department of Agriculture (USDA). This research supports the USDA priority of promoting international food security.
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