Evolution of defined microbial consortia

“What does a microbiologist call studying two organisms at the same time?…  Contamination.” (excerpt from the job talk of a recent, surprisingly successful OEB job candidate)

Although microbiologists nearly exclusively study them in isolation, microbes make their living as part of complex communities. Of the very few associations that have been addressed, some are quite important and interesting, such as the association of anaerobic methane-oxidizing archaea with sulfate-reducing bacteria. One characteristic that tends to be universally true is that these consortia tend to be tremendously difficult to study. (Visit the website of fellow OEB faculty member of Dr. Peter Girguis for his groundbreaking approaches.)

What about interesting evolutionary questions such as how consortia that cross-feed each other arise? Associations such as the anaerobic methane oxidation consortia described above have lkely existed for many millions, if not billions of years. It is too late to know which adaptations to life together came first to facilitate the establishment of the consortia. In other words, you cannott generally study grandparents to learn how freshmen fall in love. You need a novel, ‘arranged marriage’ of two bugs that specifically do not tend to spend time together in the real world.

Not surprisingly, the consortia envisioned involves Methylobacterium, this time paired with good ‘ol E. coli. How will these strange bedfellows be kept together? One will provide N for the other – and receive a C source in return. Among the many questions we hope to address are:

  • Will populations specifically adapt to their partners, or will such adaptation be general to the condition of the forced cooperation?
  • What variety of beneficial mutations will occur? Will these be of a discernably different ‘flavor’ than if left to evolve alone?
  • Will one (or both) partner in the association fall victim to cheaters?
  • Will important aspects of the coadaptation be altered with a spatially structured environment such as a plate?

At this nascent stage the possiblities for this project are wide. Despite the many potential difficulties involved, functional genomics approaches exist that can be used to begin to probe the physiologoy a two-member culture. If we cannot understand two organisms together, and how they affect each other’s evolutionary trajectories, what hope is there for comprehending the zoo within a gram of soil?