Many horizontal transmission mechanisms are regulated by social and/or ecological interactions between organisms263. It is important to note that the mechanisms involved are complex, one could easily imagine an entire course focused on this topic, and we are introducing only the broad features of these systems. Also, we want to be clear about the various mechanisms of DNA uptake. First recognize that when organisms die their DNA can be eaten, and become a source of energy, as well as carbon, nitrogen, and phosphorus, by their neighbors. Alternatively, a nucleotide sequence of a DNA molecule can be integrated into another organism’s genome, resulting in the acquisition of whatever information developed (evolved) within another organismic lineage. The study of these natural DNA import systems has identified very specific mechanisms for DNA transfer. Some organisms use a system that will preferentially import DNA molecules that are derived from organisms of the same or closely related types. You can probably even imagine how they do this – they must have receptor systems that can recognize species specific “DNA uptake sequences.” The various mechanisms of horizontal gene transfer, unsuspected until relatively recently, have had profound influences on evolutionary processes. It turns out that a population of organisms does not have to “invent” all of its own genes, but can adopt genes generated (by evolutionary mechanisms) by other organisms in other environments for other purposes. So the question is, what advantages might such information uptake systems convey, and (on the darker side), what dangers do they make possible?
263 DNA uptake during bacterial transformation: http://www.ncbi.nlm.nih.gov/pubmed/15083159