I have already posted this on chat but haven\'t got any response. A recent quest

Question

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.

QUESTIONS: 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.

Explanation / Answer

Interesting Question (glad the "group selection" post got you thinking!)

Me and two friends thought about your question during our Biology BSc at ICL (in fact we also thought about an even more puzzling phenomenon called "bacterial transformation" which is like conjugation, but they incorporate genes from dead bacteria!!) our first year course convener recognized our answers as "most likely candidates" so here they are:

1. Stress-induced Experimentation Hypothesis

The likelihood of conjugation/transformation occurring may change for a bacterial population as a whole depending on how stressed it is (or perhaps how unfamiliar the environment is?). Stress signals could cause the population to be more "risky" and take up the DNA from surrounding living/dead bacteria and incorporate it with its own genome: "the hell, we're out of options.. lets transform into something that resembles the indigenous species of this strange ecosystem!". Indeed Bacteria have memory (see: chemotaxis) this means that perhaps they can be able to tell whether they have been receiving more stress now as opposed to before, meaning they can "trial and error" with various genes that have been imported within their plasmids!

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