Washington, DC
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.
This impact story is a service of the USDA's Cooperative State
Research, Education, and Extension Service. To view other
impacts, visit
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