Social interactions in microbes

 “If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection.”

Darwin (1859)

Since Darwin, evolutionary biologists have been troubled by cooperative behavior. Why do organisms frequently evolve social behaviors that promote others at an apparent cost to their own reproduction? For example, honeybee workers labor their whole life without reproducing, birds make alarm calls, and humans often help one another. This fundamental question has received considerable attention over the last 50 years with the development of the field of sociobiology. This has resulted in a solid base of theory, centered on principles like inclusive-fitness, and a myriad of empirical tests. It is now widely accepted that cooperative behaviors evolve because they directly help the actor alongside any recipients, or they help individuals who share more alleles with the actor than predicted by chance (genetic relatedness), or both. One major group that remains relatively unexplored, however, is the microbes, whose full spectrum of sociality only recently came to light. My group studies how social environment and relatedness affects microbial behavior in a number of model systems, including biofilm-forming bacteria, slime molds and budding yeast. We find that microbes are extremely sensitive to social context - both in real time and over evolutionary time - and use them to better understand the genetic and genomics of social traits; a pursuit that is difficult in the more classical model organisms for social behavior.