Our Phages have been exhibiting some strange behaviour lately, from plaques only appearing around the edge of the plate to phage samples ceasing in producing plaques. I have successfully isolated a phage, but I have been struggling to get a large amount of the little guy. After many discussions and some research, we may have found an answer to do with the size of our Phages and their ability to diffuse through the agar.
Phages vary in size and shape greatly, from filamentous Phages which can be up to 2000 nm in length (inovirus) to the more familiar capsid and tail Phages, which can range from 26 nm to 340 nm. Phages cannot swim or move voluntarily though a medium, so their main method of transportation is diffusion. The size of a phage impacts how quickly it diffuses through a medium, and a less dense substance will allow for faster diffusion of the phage.
I noticed in the morphology of my plaques that they are all very small, pin-prick like plaques. It is possible that their inability to produce the desired web-like pattern is due to them being too large to diffuse through the agar mixture. Our lab tech has made the agar at 0.35%. According to the graph here (figure 1) this could be much too high for certain Phages to grow – larger Phages. In the lab today I plated four different agar concentrations: 0.7%, 0.35%, 0.17% and 0.085%. While the last plate may not set, my biggest hope is for the 0.17% plate.
I will post an update with the results of this experiment in the next few days. Fingers crossed!