Dear Siman,

It is quite possible that a phage isolated from an environmental sample using one host will replicate more effectively in another host. This reflects differences in the binding efficiency of phage-host cell receptors and subsequently the ability of the phage to replicate and produce new phage proteins inside the host cell. You might expect that infectivity will be restricted to a close phylogenetic group of strains or species (as they are all relatively similar), and more distant species fail all together to support the replication of the phage (as more dissimilar strains may lack critical cell surface receptors and have differences in internal regulation of transcription and translation).

You should look at some of the early phage literature where T-even phage were tested using two different Escherichia coli strains (K-12 and B). In these experiments, the progeny from K12 were tested on B and vice versa, and the difference in infectivity lead to the identification of restriction modification enzymes (REs)! REs can vary dramatically between strains of the same species, so in your phage tests, you might find that some strains allow the efficient replication of your phage (producing a clear plaque if the phage is lytic), while others only support limited replication (producing a cloudy plaque). However, if you took a sample of the phage progeny and used that to re-infect the strain, infectivity should improve.

Regards, Andrew

Andrew J Spiers Hi Andrew,

That is very helpful! By reviewing your answer I found that I missed one detail, I actually used bacteria strain A to propagate the phage A already. But still, I can get very much higher titer in strain B. I think it is still possible especially if we used phylogenetically different strains.

Hello,

I think is it normal and common, since if the phage A and bacteria A have been exposed to each other for a long time (I assume that in the natural environment they have been through evolutionary pressure) which means that bacteria A has developed defences in phage A, which are not present if phage B since it has not encountered the pathogen before.

I would not grow the phage is other strain of bacteria because you could inherently select a variant. Maybe you could do a study by passaging phage A in bacteria B, and see the effects on phage A.

Regards,

Carlos

Carlos A Valenzuela Hi,

Thank you for your inputs!