One common trait shared between humans and bacteria is that we are all infected by viruses. However, given the number of phages out in the environment, how is it that all bacteria are not wiped out by these killer viruses? The answer is that, just like us humans, bacteria have evolved to have many immune responses that are able to defend against the viral threat. In order to better understand the ways in which bacteria defend against phages, we will be isolating new phages that are able to infect Cglu that we have made “immunocompromised” by mutating phage-defense regions in the genome. We will then test to see if these phages are able to infect “immunocompetent” hosts and use these differences in phage host range to further understand bacterial immunity.
- Cglu is a soil bacterium that is most famous for industrially producing the umami flavoring MSG. It has a really interesting (and cool!) envelope structure that is composed of complex sugars and unique lipids which makes it more impermeable to stresses like antibiotics. Cglu is an Actinomycete, which is an understudied phylum of bacteria, and new phages will allow for us to study phage-host interactions and learn more about how these cool bacteria grow and divide.
|Doubling time||50 min|
Phages are usually very specific to the bacteria they infect, and they often infect by recognizing conserved structures found on the host’s surface. However, there are certain phages that instead recognize structures expressed by plasmids. (That’s why we call them plasmid-dependent phages!) Plasmids are small DNA molecules that live inside cells and can autonomously replicate and transfer between different bacteria. Because certain plasmids can live in a large variety of number of bacterial species, plasmid-dependent phages can also have a wide host range, which is special in the phage world!
In this project, we will be working with pRP4, a broad-host plasmid that can go into both E. coli and P. putida, and will use these two strains to look for plasmid-dependent phages. By isolating these phages, we hope to explore questions like: How do these phages manage to infect different hosts? and How does phage predation affect the evolution of the plasmid?
- E. coli is perhaps the most famous bacterium used in labs! In nature, it is commonly part of the normal microbiota of animals, but some strains can cause disease in humans.
- P. putida is a bacterium that usually lives in soil. It has very interesting metabolic properties which have been used for bioremediation.
- pRP4 is a broad-host, conjugative plasmid that confers resistance to the antibiotic trimethoprim. Most importantly for us, this plasmid makes its bacterial host susceptible to certain phages. pRP4 has been introduced to both E. coli and P. putida, and we will be using both of these hosts in our plasmid-dependent phage hunting mission.
|Doubling time||20 min (Eco) |
25 min (Ppu)