Bacteriophages, the viruses that prey on bacteria and are notoriously picky about which species they attack, are being put to work in an electrical bacteria sensor.
Identifying bacteria is a critical business for doctors and food safety experts, but involves either culturing the bacteria until there are enough to look at them under a microscope or amplifying their DNA. Both these processes take hours, sometimes days.
Now and colleagues at the University of Toronto, Canada, have built a sensor that detects bacteria in minutes. It consists of a positive and a negative electrode separated by a gap. Inside this 鈥渘anowell鈥� is a small amount of a bacteriophage specific to a particular bacteria species.
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When that bacteria is spotted onto the well, the phage attacks, causing a wave of dissolved metal ions to spill out. The ions change the conductivity of the well, allowing the bacteria to be detected.
The approach was in 2005 using a large, expensive sensor. Gulak鈥檚 sensor is 25 times smaller and made from silicon, so it requires the same fabrication technique as computer chips and costs just 8 cents.
So far Gulak has only detected two strains of E. coli. But the sensors take up less than a square millimetre each, so to identify unknown bacteria hundreds could be integrated onto a single chip with a different, picky phage in each well.
The work last week at the International Solid State Circuits Conference in San Francisco.
