Tag: Methods

We know you were small
Preying on Proteus too
Surprise, DNA!

by Dr Jolene Ramsey

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‘.

Phage are phriends, not phood
Not Phriendly to host, but nice
Plaques phor lab hunters

By Jolene Ramsey

Vibrio natriegens is an environmental microbe that naturally resides in marine habitats, including brackish waters and salty marshes. If you Google this bacterial species, all the top hits will tout its ‘fast’ growth. Unusual among bacteria, but common with other vibrios, V. natriegens has a  >5 Megabase genome split across two chromosomes. It also has a high count of total ribosomes, the cellular machines that make protein. As a non-pathogenic environmental organism, researchers are exploring its use in various biotechnology applications, including as a protein production system. This is one reason some are hoping V. natriegens will become the next lab workhorse in molecular and industrial microbiology that could even rival E. coli.

With an interest in improving the resources available to use in this field of research, we decided to look for bacteriophages that target V. natriegens. Bacteriophages, or phage, are the viruses that infect bacteria. Because phage rely so heavily on their host cell to copy themselves, they turn out to be extremely useful tools for probing how the cell works. As a kind of natural predator, phages can be found everywhere the host lives. The phage this Sciku is about, named Phriendly, was found in a sample collected by a college student brand-new to research on a trip to the beach.

The phage hunt process involves layering spots of environmental samples on top of growing bacteria, then looking for clear spots where the bacteria did not grow (or died due to infection) called plaques. A few of the beach samples yielded these plaques. One was a hazy, weak plaque that was difficult to propagate. We nicknamed it ‘problem phage’. In contrast, another had large, clear plaques that appeared quickly and consistently. We dubbed it the ‘friendly phage’. Following our cute tradition, we replace all ‘f’ sounds with the ‘ph’ used in the word phage to come up with the name Phriendly. Along with others, Phriendly is in a collection of phages we hope can be tools to better harvest the great potential its host microbe has for advancing biotechnology.

Original research: https://doi.org/10.1128/MRA.01096-19

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 ‘Saba, the morning breeze’.