Scientists customise viruses to kill bacteria

Thanks to a system devised by biological engineers, it is now possible to tweak genomes of bacteria-eating viruses to target specific pathogens.

The idea of setting viruses to kill specific bacteria is not knew but it was time-consuming and expensive.

With the new system phages can be customised to selectively attack specific bacteria. At the heat of the "mix-and-match" system is a standardised genetic scaffold of a bacteriophage - a virus that "eats" bacteria.

The idea was that scientists would be able to custom-build phages to target any type of pathogenic bacteria by swapping genes in an out of the scaffold.

The new system has been devised by a team from Massachusetts Institute of Technology (MIT) and features in a paper published in the journal Cell Systems.

According to senior author Timothy Lu, an associate professor of electrical engineering, computer science and biological engineering:

"These bacteriophages are designed in a way that's relatively modular. You can take genes and swap them in and out and get a functional phage that has new properties."

Lu and his colleagues hope the system would help make phages that killed bacteria for which there were no effective antibiotics.

MIT research scientist Hiroki Ando is the paper's lead author while other authors are MIT research scientist Sebastien Lemire and Diana Pires, a research fellow at the University of Minho in Portugal.

The Food and Drug Administration had approved a handful of bacteriophages for treating food products, but harnessing them for medical use had proven difficult because isolating useful phages from soil or sewage could be a tedious, time-consuming process.

Also, each family of bacteriophages could have a different genome organisation and life cycle, which made it difficult to engineer them and posed challenges for regulatory approval and clinical use.

The MIT team aimed to create a standardised genetic scaffold for their phages, which could be customised by replacing the one to three genes that controlled the phages' bacterial targets.

Many bacteriophages consist of a head region attached to a tail with which they latch onto their targets. The MIT team started with a phage from the T7 family that naturally killed Escherichia coli and by swapping different genes for the tail fibre, they generated phages that target several types of bacteria.

''You keep the majority of the phage the same and all you're changing is the tail region, which dictates what its target is,'' Lu says.