One of the more recent applications

One of the more recent applications of PCR technology is for improving national security. After the September 11, 2001 terrorist attacks on the United States, the fear of further attacks involving biological weapons increased. Rapid identification of terrorists and specific biological agents using PCR-based methods represents a plausible approach to gathering critical information about these individuals and weapons.
With the identification, characterization, and genetic engineering of viruses, bacteria, and fungi, the likelihood of strategic, harmful applications involving these organisms is growing. Biological species that represent a serious health risk to humans have been used as weapons for years. These risks can include the U.S. agricultural economy, food supplies, and the environment. To combat bioterrorism, President George W. Bush in February 2002 called for a budget increase to $5.9 billion for Homeland Security directed towards protecting against bioterrorist attacks. The creation of a national database that catalogs pathogens and individuals that are authorized to study these pathogens is also of ongoing concern. A benefit of these databases would be to identify the genetically engineered pathogens used as biological weapons (allowing quick access to specific medical treatment protocols) and to potentially link pathogens to the bioterrorists that developed them.
PCR technology can also be employed to identify the specific disease-causing microorganism. The U.S. Postal Service is working in conjunction with the biotech industry on initiatives to develop intelligent mail. Using PCR to identify anthrax, for example, is one way to quickly ascertain the nature of the contaminated mail or screen high-risk mail. This technology was the government's primary weapon against mail deemed unsuitable for circulation since irradiation provided a limited, unsubstantial solution and often damaged the mail. This high-tech strategy for mail surveillance can be particularly useful by sucking out air samples from the mail and testing for specific molecular signatures using PCR to detect a possible biological contaminant.
Defending against bioterrorism after the September 11 attacks includes developing advances in biological detection instrumentation. In conjunction with the Centers for Disease Control and Prevention (CDC), Lawrence Livermore National Laboratory and its sister laboratory at Los Alamos are currently developing DNA profiles of the most threatening pathogens such as anthrax and the plague using PCR technology. Biodetection instrumentation for genetic profiling has led to the miniaturization and subsequently the portability of DNA analytical devices, particularly for PCR. Forensic scientists and criminologists also benefit from mobile PCR machines by bringing the science to the scene of the crime leading to more rapid crime-solving capabilities.
Security at the 2002 Winter Olympic Games in Salt Lake City was led by The Biological Aerosol Sentry and Information System (BASIS). Miniaturized PCR machines called Smart Cyclers developed by a company called Cepheid were used at the field laboratory operation set up by BASIS. The purpose was to prepare for a bioterrorism threat by having appropriate and rapid biological sample identification to allow for accurate bioterrorist assessment and validation so that the proper responses could be executed.
Recent concerns over genetic engineering of agricultural food products and the potential risks to food safety have prompted studies investigating the molecular signatures of crops using PCR. A study in the scientific journal Nature revealed that genetically manipulated DNA from industrial produced maize had been introduced into corn fields in Oaxaca, Mexico. Although the ramifications to health and food safety are unknown and most likely benign, surveillance of crops using PCR is a formidable approach in the implementation of security measures to help protect against harmful pathogenic contaminations that can threaten food safety. As the cost and use of PCR are eased and as the collection of databases with recognizable DNA profiles of various microorganisms is increased, the utility of this technology in human and food safety will be greatly improved.
Motility test medium demonstrates if cells can swim in a semisolid medium. A semisolid medium such as O.75% agar is inoculated with the bacteria in a straight-line stab with a needle. After incubation, if turbidity (cloudiness) due to bacterial growth can be observed away from the line of the stab, it is evidence that the bacteria were able to swim through the medium.

Figure 8. Bacterial cultures grown in motility test medium. The tube on left is a non motile organism; the tube on right is a motile organism. Motility test medium is a semi-soft medium that is inoculated with a straight needle. If the bacteria are motile, they will swim away from the line of inoculation in order to find nutrients, causing turbidity or cloudiness throughout the medium. If they are non motile, they will only grow along the line of inoculation.