Problem:

I have already posted this on chat but haven't got any response. A recent question on group selection stimulated me to ask this here.

Required:

Question: Why should bacteria conjugate? If we consider that a bacterium is another bacterium's rival (in terms of obtaining resources) why should a bacterium "share" it's antibiotic resistance gene, for example, with another bacterium?

I can think of 2 reasons. One is group selection, and the other is "Gene Selection". Group selection has been highly criticized in recent years, and individual selection has dominated thinking, but here my support goes for gene selection rather than individual selection.

Gene selection seems to me the easier explanation over individual selection. Even if we consider the fact that a colony is made from divisions of single cells and the cells are extremely similar and also that conjugation is more probable between cells of a colony, we should also consider that conjugation can happen between very different bacterial species.

Any ideas? Or better yet, pointers to places where this has already been answered?