I liked the question about F' and R plasmids.
What is a good resource that describes what is known about the functions and diversity of plasmids in the wild? Prokaryotes or eukaryotes?
Wikipedia points to five kinds of plasmids (fertility (F), resistance (R), col plasmids (offensive genes that let a bacteria kill other bacteria), degradative function plasmids, and virulence plasmids). There is a brief section on yeast/euk plasmids too. It seems like plasmids could actually convey nearly any gene. Restriction enzymes are found mostly on plasmids and they would seem to be defensive - maybe those are degradative.
Are there references that are more detailed and nuanced?