Rights: © Copyright. University of Waikato. All Rights Reserved. Published 9 September 2016 Download

ESR scientist Dr Brent Gilpin explains that a bacteriophage, or phage, is a virus that infects bacteria. He describes how a phage can be easily detected in the lab by plating bacteria on an agar plate. When clear spots appear on a ‘lawn’ of bacteria, it shows that the phage has infected and killed areas of bacteria.


A bacteriophage, or a phage, is a virus that infects bacteria, so these don't infect human cells –they are very specialised and only infect bacteria. So every bacteria is being attacked by various viruses which are using those as the host that they replicate in. The bacteriophages are different to the eukaryotic viruses because, to detect a virus that infects your eye, ideally you need to infect it into your eye, or else a human cell tissue culture line, which isn't exactly the same as your eye. Whereas a bacteriophage infects bacteria, and bacteria we can grow in the laboratory rather easily. So the entire organism can be grown on a plate, and if you add a mix of bacteriophage with the bacteria, you will see on the plate which doesn't have bacteriophages it will be a lawn of bacteria, whereas wherever there is holes in that plate of bacteria, it indicates that a bacteriophage has infected those and has killed all the bacteria in the vicinity, which is effectively what bacteriophages do. They get into the cell, reproduce themselves and then bust that cell open, killing the bacteria, and then go and find some more hosts to infect.

John E. Wertz, E.coli Genetic Stock Centre, Yale University
Hans-Wolfgang Ackermann
Dr Martin Philpott
The New Zealand Biotechnology Hub
Dr Richard Hunt
A.J. Cann