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Scientists Examine Genetic Clues to Help Biocontrol Agents Survive Longer

Media Contact:
Jennifer Martin, (202) 720-8188

June 22, 2009

For years, producers have used biological control agents as a sustainable, environmentally-friendly way to keep their plants disease- and pest-free.  While this method can reduce the use of pesticides, there is one downside: the short lifespan of the control agents in the soil.

Researchers, funded in part by USDA’s Cooperative State Research, Education, and Extension Service (CSREES), have identified genes in one biological control agent – the bacterium Pseudomonas fluorescens – that are related to the organism’s survival in soil and on plant surfaces.  Their work could lead to the production of more effective biological control agents.  P. fluorescens isolates protect a range of crop plants against diseases, including protection of wheat against take-all disease.

The study found that among the three genome sequences compared, there was much similarity in genes located near the origin of replication and many differences in genes near the section of the DNA where replication terminates.  These differences may help the bacteria survive under different environmental conditions.  It also suggests P. fluorescens doesn’t belong to a single species, but rather to a species complex.

“The use of whole genome sequence analysis has given a fascinating view of the variability of P. fluorescens and points the way forward to new and powerful ways to categorize microorganisms,” said Dr. Mark W. Silby, research associate professor of microbiology at Tufts University.

By comparing three different sequenced genomes of P. fluorescens, researchers discovered several sections of the bacteria’s DNA where genes are located on both strands of the DNA structure.  These sections give the researchers new clues to understanding how the bacteria survive in natural environments and build upon findings of another study recently published by the Tufts University researchers.  The scientific community previously thought that gene expression could only occur from one of the strands of DNA in bacteria.  Gene expression from both strands of DNA of one section had previously only been identified in viruses and ‘higher-level’ organisms, but not in bacteria.

“The confirmation that the bacteria can express two proteins from the same section of DNA is exciting and demonstrates the versatility of this organism and its great potential as a pest control agent,” said Tufts University professor of molecular and microbiology, Dr. Stuart B. Levy.

According to North Carolina State University’s Biological Control Information Center, biological control is human's use of a living organism (a predator, parasite or pathogen) to control a particular pest. Biocontrol agents include arthropods, vertebrates, nematodes, fungi, protozoa, bacteria and viruses.   

The work was completed by researchers at several institutions, including Tufts University School of Medicine, U.S. Department of Energy, Wellcome Trust Sanger Institute in the United Kingdom and Massey University in New Zealand.  CSREES provided funding through the Microbial Functional Genomics program.

Through federal funding and leadership for research, education and extension programs, CSREES focuses on investing in science and solving critical issues impacting people's daily lives and the nation's future. For more information, visit www.csrees.usda.gov.

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