8 thoughts on “P74 – Bean

    1. Hi Renee. Thank you for your comment.

      The clear bordered plaque indicates that McStabberson phage entered a lytic lifecycle rather than a lysogenic lifecycle. This is significant because it demonstrates that McStabberson successfully lysed (killed) the bacterial host rather than integrating its DNA into, and replicating with the bacteria, the former being the desired effect when exploring phage as a therapeutic treatment for bacterial infections. If McStabberson produced a turbid plaque or a plaque with a clear center and turbid halo it would be evidence that McStabberson had, at some point, entered a lysogenic lifecycle which means the bacteria was still able to replicate and therefore not knocked out by the phage. In a human patient with a bacterial infection undergoing phage therapy, it would not be helpful for the phage to do anything but lyse the cell.


  1. If you could go back and change one element of your experiment, what would you like to change?

    1. Hi Lio. Thank you for your question. Knowing for sure whether or not our hypothesis that McStabberson is a B7 subcluster phage is correct would be ideal. So having B7 available in the lab to test McStabberson against would definitely be the first change I’d make. I’d also probably go back and repeat DNA isolation because it’s possible that the quality of our DNA could be higher to enhance restriction digest results and maybe give us a more accurate estimate what cluster McStabberson belongs to.

  2. How does the average head and tail size noted in the Electron Microscopy relate to similarity of the B7 sub cluster phages? (I think that is what you said, not sure if I got it right though!)

    1. Hi Nickolette. Thank you for your question. I answered it, and now my response has gone away so I apologize in advance if 2 replies show up.

      You are correct, I did say that our EM results and those of two other phage, Saguaro and Tapir, support our B7 subcluster hypothesis. It has less to do with the head and tail measurements and more to do with the fact that Saguaro and Tapir are both B7 subcluster phages that the phage enzyme tool provided as being 80% similar to McStabberson. When looking at the EM photos of those two phage, they look very similar to McStabberson and share the siphoviridae morphotype. We don’t know for sure, as B7 was not available for PCR, but it helps to know that on top of the 80% similarity they also look alike.

      Thanks again for your question.

  3. What do you think the results would be for the infection test without lsr2 proteins?

    1. Hi Ash. Thank you for your question. It’s a really good one and pretty challenging to answer.

      The study I reference used M. smeg bacteria and Muddy phage to test Lsr2 protein function on phage ability to inject DNA into the host. The study found that Lsr2 protein function is required for phage infection. My understanding is that without Lsr2 protein function, the phage is unable to lyse the host cell. Since McStabberson was able to lyse M.smeg I suspect that without Lsr2 proteins it would only enter a lysogenic cycle and not lyse the host. But that’s why the future experiments would be interesting! What if we found a phage that doesn’t require Lsr2 protein to lyse the host? Perhaps those genes that don’t require Lsr2 in Mcstabberson can be used in other phage against bacterial infections that inhibit Lsr2 protein function as a defense against phage infection. I’ve linked the study below if you’re intersted.

      Dulberger, C.L., Guerrero-Bustamante, C.A., Owen, S.V. et al. Mycobacterial nucleoid-associated protein Lsr2 is required for productive mycobacteriophage infection. Nat Microbiol 8, 695–710 (2023). https://doi.org/10.1038/s41564-023-01333-x

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