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Nathan Myers

We could consider mosquitoes and biting flies to be macroscopic predators that overwhelmingly outnumber their prey. (Some might object to calling a no-see-um macroscopic, but not here!)

But at our favored microscopic scale it gets hard to know how to count individuals. All the identical virions and all the identical bacteria in a sample might be thought of as one individual each, from a selection standpoint. ("Not all organisms are as blessed with perimeters as you are.") The size of each such "individual" might be measured in daltons or in aggregate surface area, depending on context, and the population would depend on the mutation rate and resulting genetic diversity. E.g. HIV in a patient is a large number of very small organisms, where malaria or herpes may amount to a few larger ones.

If it is advantageous to have virions plentiful in one's mucus, there ought to be advantages to the epithelial cells coding them directly, presuming the cells can generate enough diversity. It would seem very hard to support a claim that this does or does not occur anywhere in nature, not least because (as I am led to believe) viral sequences are routinely and automatically edited out of genetic-sequencing results, assumed to be contamination, so that no such result can be trusted, positive or negative.

Merry replies: Yeah! Our favored microscopic scale! but first, I want to acknowledge your macroscopic example of many predators per prey. However, if we want to split hairs, one could argue about how to define prey. Does an organism have to be killed in order to be considered prey? Are we mosquito prey or lunch? Try to draw a line here and it will get blurry fast.

As to the advantages of epithelial cells coding the viruses directly, the work so far has focused on phages that infect bacteria, not viruses that infect and reside within eukaryote cells. But following the thread of your thought, I note that in a sense epithelial cells CAN and DO maintain a population of phages, albeit indirectly. Those mucus-producing epithelial cells have various ways of selecting and favoring populations of desired bacterial symbionts. These bacteria in turn are likely lysogens carrying phages within as prophages integrated into the bacterial chromosome. Thus the epithelial cells are hosting bacteria that do the work of tending to the phages. Indeed, the researchers publishing the work described in this post think that these complex relationships will turn out to be even more important, and they will be trying to investigate this --- a more difficult challenge.

Thanks for your loyal readership and thought-provoking comments.

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