Public health inspectors and food manufacturers need to know
quickly whether food is safe to eat or process. Food
contaminated with bacteria such as Listeria monocytogenes or
Escherichia coli is only unsafe if the organisms are alive, and
standard tests to distinguish live bacteria from dead ones
usually take between one and three days. But researchers are
developing a test based on a gene probe that can do the job in a
matter of hours. Gene probes are strands of nucleotide bases,
the building blocks of DNA. If the bases are in the right order
in the strand, they can bind to other 'complementary' strands of
DNA in a test sample. Probes are designed to bind exclusively to
DNA from a target organism such as L. monocytogenes. Radioactive
tracers or substances that change colour in certain
circumstances can be attached to the probe to show if the target
DNA is ... To continue reading this article, subscribe to
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