Microbes don't play solitaire: how cooperation trumps isolation in the microbial world.

Abstract

Primitive cells did not carry a stable organismal genealogicaltrace. Primitive cellular evolution is basically communal. Thehigh level of novelty required to evolve cell designs is aproduct of communal invention, of the universal HGT field,not intralineage variation. It is the community as a whole, theecosystem, which evolves.– Woese (2002)