Sequencing the Bad Guys
A high-tech piece of equipment, hard work, and collaboration have brought
researchers a few steps closer to developing new tests and vaccines
for several troublesome cattle diseases.
Scientists at ARS' Bacterial
Diseases of Livestock Research Unit in Ames, Iowa, and the University
of Minnesota (U-M) have sequenced the chromosomes of two disease-causing
microbesthose that cause Johne's disease and bovine brucellosisand
have moved into the finishing phase of work on an agent that brings
about leptospirosis. That project is being done completely within the
ARS unit, which is part of the National Animal Disease Center (NADC).
The arrival at Ames of a DNA sequence analyzer has made much of this
work possible. "Our sequencing capacity was a limiting factor for
large-scale projects," says ARS veterinary medical officer David
Alt, who operates the analyzer. "Now we can perform almost 800
reactions a day." The sequencer can automatically analyze multiple
runs of 96 DNA samples, making unattended 24-hour operation possible.
Alt compares a sequenced genome to a book. "We can read the book
from start to finish," he says. "We are not going to understand
every word in it, but it's a starting point that may lead to treatments,
vaccines, and diagnostic means that are better than those currently
Automated sequencing allows for rapid analysis of an organism's genes,
speeding identification of those linked to superior characteristics
or to negative traits such as susceptibility to disease. Scientists
and breeders can then, theoretically, root out or exploit specific genes
to breed improved varieties or species. The Ames/U-M research seeks
to identify genes that are associated with disease and that show potential
in vaccine development.
NADC's first sequencing project was on Mycobacterium paratuberculosis.
That microbe causes Johne's disease, an intestinal disorder characterized
by diarrhea and weight loss in infected cattle and found in 7 percent
of beef herds and 22 percent of dairy herds nationwide. ARS microbiologist
John Bannantine and Vivek Kapur, a U-M pathogenomics scientist, led
"With the sequencing," says Bannantine, "we hope to
understand the biology of M. paratuberculosis, identify unique
disease-causing genes, andmost importantlydevelop new diagnostic
ARS microbiologist Shirley Halling led sequencing work on Brucella
abortus, which causes bovine brucellosis. This highly contagious
bacterial disease induces late-term abortions and infertility in cows.
It can also bring about undulant fever in humans.
The sequencing of Leptospira borgpetersenii serovar hardjo,
a cause of leptospirosis, is being led by ARS microbiologist Richard
Zuerner. Leptospirosis causes abortions, stillbirths, and weak offspring
in cattle and swine and can reduce milk production in cows. It also
affects many other animals, including dogs, and is an important public
health concern.By Luis
Pons, Agricultural Research Service Information Staff.
This research is part of Animal Health, an ARS National Program
(#103) described on the World Wide Web at www.nps.ars.usda.gov.
"Sequencing the Bad Guys" was published in the April 2003 issue of Agricultural Research magazine.