SEA-PHAGES | Different Plaque Sizes for One Phage

Link to this post \| posted 03 Dec, 2021 13:31
dominick0	I have recently isolated a bacteriophage for E. coli from soil. The phage has been purified through 6 rounds of serial dilution and has given consistent plaques after the second purification. That is why my professor and I consider it as isolated. The only issue is that it always displays two distinct plaques: a large, clear one of about 0.5 cm and a smaller clear one of about 0.2 cm. There are no sizes in between. It is either or. When I tried to take bacteriophages from the small and from the large plaques, I resulted in the exact same two plaque sizes. Taking from these as well still gave one large and one small. It has been my understanding a phage gives only one unique plaque size which is dependent on absorption rate into the cell, not two distinct plaque sizes. Does anyone have any ideas why this is happening?

Link to this post | posted 03 Dec, 2021 13:31

I have recently isolated a bacteriophage for E. coli from soil. The phage has been purified through 6 rounds of serial dilution and has given consistent plaques after the second purification. That is why my professor and I consider it as isolated. The only issue is that it always displays two distinct plaques: a large, clear one of about 0.5 cm and a smaller clear one of about 0.2 cm. There are no sizes in between. It is either or. When I tried to take bacteriophages from the small and from the large plaques, I resulted in the exact same two plaque sizes. Taking from these as well still gave one large and one small. It has been my understanding a phage gives only one unique plaque size which is dependent on absorption rate into the cell, not two distinct plaque sizes. Does anyone have any ideas why this is happening?

Link to this post \| posted 03 Dec, 2021 15:32
debbie	Dear , It is a common morphology for some of our phages to do this. Six rounds of replating a well isolated plaque means you have purified well. Our Cluster A phages are notorious for doing this. I think that they are the same plaque morphology and it is the landscape differences that do this OR just as likely, it is a cell growth issue and not cells are in the same growth period when infection started so some plaques have a head start on the others. What is 'dangerous' is to 'over-purify' and find the clear plaque mutant that has lost /integration function. If there is a genotypic difference between the 2 populations, a good Illumina sequence run may show it. debbie

Link to this post | posted 03 Dec, 2021 15:32

debbie

Dear ,
It is a common morphology for some of our phages to do this. Six rounds of replating a well isolated plaque means you have purified well. Our Cluster A phages are notorious for doing this.
I think that they are the same plaque morphology and it is the landscape differences that do this OR just as likely, it is a cell growth issue and not cells are in the same growth period when infection started so some plaques have a head start on the others.
What is 'dangerous' is to 'over-purify' and find the clear plaque mutant that has lost /integration function. If there is a genotypic difference between the 2 populations, a good Illumina sequence run may show it.
debbie

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Different Plaque Sizes for One Phage