Analyzing How Viruses Infect Bacteria in Vivo

Viruses are known to be the most widespread invaders on the planet. Some of them are specialized in attacking animals, including humans, and others mostly attack plants. But a new study looks at the more common, yet less-understood instances when viruses infect bacteria.

An entire class of viral agents, called bacteriophages, or phages, specializes in infecting bacteria. While experts have known about this for a long time, thus far they've had a tough time studying these microscopic interactions.

Cultivating bacteria and viruses while cutting them from their environments – in vitro cultivation – is tremendously complex with these microorganisms, and so the interactions that develop between them have been studied only superficially.

In the newest study, investigators from the California Institute of Technology (Caltech), in Pasadena, have developed a new approach to studying virus-bacterium interactions in vivo, in dedicated, highly-controlled lab settings.

Details of the research effort appear in the July 1 issue of the top journal Science. The work was made possible by funds provided by the US National Science Foundation (NSF). The research team was led by Caltech expert Rob Phillips.

In order to enable the study, experts used six-nanoliter chambers to store cells collected from the posterior part (hindgut) of a termite. An array of 765 chambers was put together, and then the bacteria and the viruses were added in the mix.

Experts then used established techniques to determine whether each of the chamber contained bacterial DNA, viral DNA or both. The team was able to record a large number of significant virus-bacterium, interactions. Their work is bound to push this field of research further.

“In some cases, the host was associated with a viral gene exhibiting marked diversity, suggesting possibly a more ancient infection, a more susceptible host or a phage replicating at a lower fidelity,” a NSF press release reads.

“By analyzing the bacteria and viruses based on their evolutionary development they were able to deduce that horizontal gene transfer, while it may be occurring, is not occurring at a rate high enough to randomize host-virus associations,” the document adds.