Microorganisms
From Wiki Against Mines
The text on this site is published with permission of RAND and taken from "Alternatives of Landmine Detection" Jacqueline MacDonald et.al, RAND report, ISBN 0-8330-3301-8, Document Number: MR-1608-OSTP, Year: 2003
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Bacteria
Bacteria are special microorganisms. In different scientific projects they are investigated for their suitability for the detection of explosives.
Description:
During the 1990s, researchers engineered a strain of bacteria that fluoresce in the presence of TNT. A regulatory protein in the bacteria recognizes the shape of the TNT molecule and fluoresces whenever the molecule is present. In principle, a bacterial mine detection process would involve spraying bacteria on the mineaffected area, possibly using an airborne system. The bacteria would be allowed to grow for several hours. Then, a survey team would return to search for fluorescent signals. The search could be conducted either from an airborne system or using a handheld fluorescence detector. One field trial using bacteria has been conducted. Five targets containing from 4 oz to 10 lb (100 g to 5 kg) of TNT were placed in a quarter-acre field site. The bacteria detected all five targets, but there were also two false alarms. Based on this single field trial, it is not possible to determine the lowest concentration of explosive that bacteria are capable of detecting.
Strengths:
Like chemical sensors, bacteria can be engineered to be highly specific to the explosive of concern. The regulatory protein that causes the bacteria to fluoresce recognizes only TNT and structurally similar molecules. Thus, this method has the potential to reduce false alarms from clutter objects. An additional advantage is that it may allow coverage of a large area in a relatively short time. In theory, the unit cost of this method should decrease as the size of the search area increases.
Limitations:
The limited research to date has revealed possible environmental limitations of this method. Bacteria are highly sensitive to environmental conditions. The existing strain used to locate TNT cannot survive at extreme temperatures. In addition, the method functions only in moist soil because dry soil quickly absorbs the bacteria. Another limitation is that the potential for false alarms is unknown. For example, the two false alarms in the single field test could have resulted from the migration of explosives away from the targets or from some other chemical in the environment that triggered the fluorescent response. An additional problem in experimental trials was that the fluorescence detector missed some of the signals from the bacteria. Finally, the performance potential of this method will be limited by the fate and transport of explosives in the subsurface. If the explosives migrate away from the mine, then the bacterial signal may occur at a distance from the mine. In addition to these operational limitations, public concerns about introducing genetically engineered organisms into the environment may limit the application of bacteria in mine detection.
Summary and evaluation:
The potential for using bacteria in mine detection remains largely untested, except for the single field trial referenced in Appendix R. Nonetheless, continued investigation is warranted as long as clear decision points for terminating or continuing funding are established. For example, if research shows that environmental confounding factors (such as moisture conditions and temperature) preclude the use of bacteria in all but an ideal environment, then research may need to be halted unless bacterial strains can be bred to overcome these limitations.
