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Entomologist Denny Bruck injects a larva of the
tobacco hornworm, Manduca sexta, with P. fluorescens Pf-5.
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Gene Clusters Offer Potential Protection against Plant
Diseases
By Laura
McGinnis
April 11, 2008 New research supported by the
Agricultural Research Service (ARS) has
revealed novel pseudomonad compounds and toxins with potential benefits for
plants and people. Pseudomonads are a diverse group of bacteria, some of which
harm plants and animals, while others are beneficial.
Within every genome, there are chunks of DNA whose functions are unknown.
Some of these are similar to genes that make natural products. Because
scientists don't know which specific natural products these genes make, these
segments are known as "orphan gene clusters."
According to
Joyce
Loper, a plant pathologist at the ARS
Horticultural
Crops Research Laboratory in Corvallis, Ore., it's likely that some orphan
gene clusters produce natural products that could become new antibiotics.
Identifying these gene clusters and their products would give scientists new
tools that can be used to fight harmful microorganisms.
Working with scientists at Scripps
Institution of Oceanography at
University of California-San
Diego, Oregon State University, and
Northland College in Ashland,
Wis., Loper investigated a new method for determining the products of orphan
gene clusters.
The scientists used what they call a "genomisotopic" approach,
which combines genomic sequence analysis and isotope-guided fractionation, the
process of isolating compounds.
Loper and her colleagues applied the genomisotopic method to the genome of
the bacterium Pseudomonas fluorescens Pf-5, a biological control agent
that protects plants from diseases. Scientists have long known that Pf-5 makes
antibiotics, but by using the method, they've identified two antibiotics that
had never been seen before.
These studies were funded jointly by ARS, the National Institutes of Health, the
German Research Foundation, and the
Microbial Genomic Sequencing Program, an initiative of the USDA Cooperative
State Research, Education and Extension Service (CSREES). In 2007, CSREES funded the
sequencing of seven additional Pseudomonas species, four of which are
under investigation in ARS laboratories.
Further research could identify new natural products with valuable
properties, with potential for use in antibiotics, drugs or pesticides.
Read
more about this research in the April 2008 issue of Agricultural
Research magazine.
ARS is the U.S. Department
of Agriculture's chief scientific research agency.