I try to isolate human phages against Staphylococcus capitis and Micrococcus luteus, both found on human skin. First, I take sterilized and moistened swabs (with 0,9% NaCl) and rub it on a defined surface area of 16cm^2 on the forearm, face and scalp. Then, I transfer the swabs to 5 ml of phage buffer, shake it vigorously and filter it through a 0.2µm membrane.
To test if there are phages I do the spot assay and dispense 3 drops of 5µl of the samples on a S capitis lawn.
I already tested bacteriophage spot assays of e coli and it worked well.
I think the phages of s capitis and m luteus on the human skin may be lysogenic. Can someone reccomend how to induce the lytic cycle or has someone already experience in isolating human skin phages?
Thank you!!
hello, think you have to concentrate phages at first after , you have to incubate phage suspension with specific bacteria, than after over night incubation centrifuge it 5000g 20-30 minutes than take supernatant and filter it through a 0.2µm membrane.
First of all even lysogenic phages will still form plaques quite nicely, it is just the plaques are a bit turbid rather than being really clear like with a lytic phage. So if you are not seeing any phage lysis at all, that probably is the real answer.
However if you want to test to see if you induce any lysogenic phage from some strains, most will be induced by some agent that induces DNA repair, classically this is UV irradiation or mitomycin C induction are the traditional ways. Not every lysogenic phage is induced this way, but the vast majority are.
Note however that if strain A carries a lysogenic phage and you induce it, it will not form plaques on any other strain that is also a lysogen for the same phage.
https://academic.oup.com/femsmicrobes/article/doi/10.1093/femsmc/xtab003/6204716#235345021
Hope this paper will help you for isolation. Isolation and characterization of bacteriophages from the human skin microbiome that infect Staphylococcus epidermidis.
Thankyou
Thank you for all your answers! I will try some modifications :-)
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