We know you were small
by Dr Jolene Ramsey
Preying on Proteus too
Surprise, DNA!
Bacteriophages, or phages, are the viruses that infect bacteria. They come in different shapes and sizes, but are often icosahedral (spherical) and tailed. A tailed phage is structured like a filled lollipop, where the candy represents the phage head, the filling represents the nucleic acid genome, and the stick is like the tail. The overwhelming majority of phages scientists and students have discovered up to this point are tailed with a DNA genome, largely due to bias in our sampling methods. Recent investigations suggest many phages with RNA genomes remain to be isolated, and they were hypothesized to be small and round, similar to the ones that are already known. We want to find them.
In a very focused hunt, we looked for small RNA phages against the human opportunistic pathogen Proteus using a filtration selection method. After a few rounds of selection, there was a prime candidate that was definitely small, but it didn’t pass the other tests that define RNA phages. It was a puzzle. For clues, we looked at the phage shape in the electron microscope. To our astonishment the phage had a tail and a very small head! We immediately verified that it had a DNA genome as well. Though the search was a failure, we put phage Saba in the arsenal for use in other projects. To fully survey the diverse kinds of phage in the environment we will need to develop and refine targeted and general protocols for phage isolation. This will give us the most accurate picture of the phage universe.
Original research: https://doi.org/10.1128/MRA.01094-19
Jolene Ramsey studies bacterial viruses (phage) as a Center for Phage Technology postdoctoral researcher. She tries to understand how phages orchestrate their escape plan at the molecular level. You can catch up with her on Twitter: @jrrmicro
Enjoyed Jolene’s sciku? Check out her excellent sciku ‘Privateer, the phage’, ‘TF gets in on the bud’, ‘Click click go!’ and ‘The Phriendly Phage‘.