Gene-edited bacteriophages, or viruses that attack bacteria, can make potentially dangerous microbes in food and water glow so they are easier to detect.
In the United States and the United Kingdom, drinking water must contain no Escherichia coli bacteria, which can cause food-poisoning. But methods for testing water for such potentially dangerous bacteria are either time-consuming or do not reliably detect low microbial concentrations. at Cornell University in New York and his colleagues wanted to use bacteriophages as biological nanobots that latch onto bacteria and make them more detectable.
A bacteriophage injects its genome into the bacterial cells it targets. The viral DNA then prompts the bacterium to repeatedly duplicate the virus until it exhausts its energy reserves and dies.
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The researchers set out to alter the genome of a bacteriophage that naturally attacks E. coli so the infected cells would produce compounds that make them easier for us to detect.
They used the gene editing tool CRISPR to make two alterations to the bacteriophage DNA, the first of which causes the infected E. coli to produce a glowing compound similar to those produced by some deep-sea shrimp. This meant that when the researchers added bacteriophages to a sample of water or liquefied food, it caused all the infected E. coli bacteria in the sample to visibly light up.
The team鈥檚 second tweak to the bacteriophage鈥檚 genetic code changed the structure of the viral duplicates made inside the E. coli so that that they would easily stick to cellulose films or tiny magnetic particles. This change meant that the infected bacteria were easier to collect from a liquid sample, as the researchers could now count on them getting stuck to a filter or being drawn towards magnetic particles they added to the water or liquefied food sample.
In experiments using samples of water collected from a local municipal source and with spinach leaves liquefied by enzymes, the gene-edited bacteriophages were sensitive enough to detect as few as five bacteria in 100 millilitres. This detection procedure only took about half the time typically required by more traditional methods.
at the Lawrence Berkeley National Laboratory in California says that using bacteriophages is advantageous not only because they work quickly, but also because nature already contains abundant bacteriophages that specialise in finding and attacking most bacteria. However, he says a potential disadvantage is that bacteriophages may specifically target one strain of bacteria, which could be a problem in situations where it would be helpful to detect many bacterial strains at once.
In a presentation at the in San Francisco, California last week, Nugen said that this problem can be overcome by genetically engineering bacteriophages to be more like hybrids of different virus varieties. He said his team has already made bacteriophages that also aid in the detection of bacteria like Listeria and Salmonella.
鈥淣ow, people are looking in sewage to find new bacteriophages, but what I think we鈥檙e going to be doing in the very near future is designing and engineering brand-new bacteriophages from the bottom-up,鈥� he said.
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