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Team:Edinburgh
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Revision as of 00:16, 9 October 2009
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iGEM PROJECT "TNT/RDX Biosensor and Bioremediator"
In 2007, 5 426 new casualties were recorded from landmine explosions. 71% of these casualties were civilians. A further 46% of the civilian casualties were children[1]. This made us realise the need for the production of a cheap, safe and accurate method that can be applied in a big scale to help detect landmines. A synthetic organism could be just what is needed.
Even though landmines are buried under soil, they normally leak indicating their imminent position with a chemical fingerprint. TNT-filled landmines produce three major source chemicals, namely 1,3-DNB, 2,4-DNT, and 2,4,6-TNT [2]. In addition, the natural degradation of explosive compounds, such as TNT, by bacterial enzymes produces nitrogen in the form of Nitrites[3]. Nitrites are also one of the by-products of the degradation of another explosive used in landmines, namely RDX. In the latter case, this can be achieved by the soil bacterium Rhodococcus rhodochrous[4].
Our project is concerned in making a biosensor that would detect both the presence of TNT and nitrites/nitrates.
Natural nitrite concentration in soil tends to be very low (below 0.1 mg NO2-N /kg)[5]. Thereby the possibility of false positive results decreases. Our biosensor would also detect nitrates but these would need to be at a much higher concentration than nitrites to bring about a response.
The fact that excessive fertilisation with ammonium producing fertilizers such as urea can cause an increase in the presence of nitrites in the soil [6] gives the possibility that our device can be used in diverse fields of interest, from landmine identification (ranging from TNT landmines to RDX ones), to assaying extent of fertiliser induced nitrite/nitrate pollution.
Please read our detailed project description and part characterisation for further details.
Why we differ?
Existing systems
Biological systems for mine and particularly TNT detection have been described previously, the most prominent of which is the patented Microbial Mine Detection System (MMDS) developed by Dr Paul Burlage and the Oak Ridge National Laboratory. The MMDS is normally a bacterium able to detect and exhibit chemotaxis towards TNT and the vapours released as a result of its degradation, in particular nitrates and nitrites. The bacteria utilized at the Oak Ridge Laboratory are mainly the Bacillus or Pseudomonas species, such as Pseudomonas putida, which have been found to naturally exhibit growth towards a source of TNT degradation. Although the MMDS patent states that the recombinant microorganism is able to directly detect TNT, it is likely that the bacteria do no exhibit chemotaxis towards TNT per se but rather the organism is sensitive to high levels of nitrate and nitrite. The sensitive genes are in turn fused with a Green Fluorescent Protein (GFP) reporter gene, making it possible to visualize the fluorescent bacteria with the help of a UV illuminator. The MMDS has been field tested at a South Carolina site, where the system was able to locate all five of the hidden mine sites, showing the great potential of biological mine detection (Fig. 1).
