For public health and law enforcement officials responsible for monitoring disease outbreaks, and determining whether an outbreak is a natural occurrence or a criminal act, it is often difficult to make a swift and clear distinction between suspect bacteria with similar features. Recently, scientists at Los Alamos National Laboratory devised an improved analytical method for distinguishing Bacillus anthracis (the bacterial cause of anthrax) from its close cousins Bacillus cereus, which is less deadly and Bacillus thuringiensis, which is usually benign.
In research published in the current issue of Applied and Environmental Microbiology, Los Alamos scientists Yulin Shou, Thomas Yoshida, and Babetta Marrone, along with Wenwan Zhong, a former Los Alamos postdoctoral student now at the University of California Riverside, describe a process for analyzing DNA fragments in the enzyme digestions of Bacillus bacteria using pulsed field gel electrophoresis. Pulsed field gel electrophoresis (PFGE) is a method for separating nucleic acid molecules, such as those found in DNA, through use of an alternating electrical field. After PFGE separation, the scientists use computational analyses to differentiate the Bacillus species from each other based on their unique DNA “fingerprint” patterns.
“This process” says Marrone, “makes it much easier to tell the three bacteria apart. Traditionally, the structural and biochemical similarities of the bacteria have made them difficult to differentiate using standard microbiological techniques. Those similarities often slow down the analysis process at a time when delays might be costly to public health or law enforcement.”
PFGE is widely used by public health laboratories and forms the basis of PulseNet, the Center for Disease Control’s network for the surveillance of food borne disease outbreaks. The new method developed by Los Alamos would add to the toolbox of methods already available to public health laboratories for molecular characterization of common food borne bacteria, such as E. coli O157:H7. It could also be used to supplement more detailed molecular methods used by bioterrorism response labs for differentiating between highly similar strains of Bacillus anthracis.
The computational analysis process involves using advanced data analysis techniques to analyze and classify the DNA fragment patterns and store them in a database. Because each of the Bacillus bacterium is digested differently by the enzyme, the fragment patterns they produce are also different.
The work is a collaboration between researchers working in the Laboratory’s Chemistry and Biosciences Divisions and builds upon Los Alamos’ extensive expertise in the genomic analysis of B. anthracis for national security.
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and the Washington Division of URS for the Department of Energy's National Nuclear Security Administration.
Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.