Microbial Population Biology

Welcome students, guests, and outside experts to Microbial Ecology and Evolution, eventually to be renamed Microbial Population Biology, in the spirit of the long-running Gordon Research Conference on Microbial Population Biology. I think this name change is appropriate because the most important concept that differentiates this class from other classes in Microbiology or Genetics is that microbes, being so small, hardly ever exist as individual study subjects, but rather exist as populations. These populations can be composed of many (>10E8) cells that may be virtually identical and hence share common interests, but they may also comprise different genotypes or species with selfish, even antagonistic interests. Therefore, one key to understand microbes in the real world is something Ernst Mayr coined “population thinking.”

Population thinking is probably not how you’ve been taught or how you’ve typically thought of biological phenomena. Nearly all courses describe the mechanism, or the gene, or the reaction. But what about alternative mechanisms, genes, or reactions? Population thinking means that biological phenomena ought to be considered as outcomes of interactions among many variable individuals. These interactions can be driven by:

• ecology: at levels ranging from neighboring cells to landscapes
• population genetics: by natural selection, genetic drift, migration, or recurrent mutation
• behavior: as cooperation, cheating, parasitism, or antagonism
• chance or catastrophe

So, take a minute to think of your favorite biological phenomena or organism, and consider the alternative possibilities. What else might arise or exist in that population? What other variants might influence that phenomenon?

In this class, we will consider some of the most important and most fascinating properties of microbes: their diversity, where they live, how and why they evolve, how and why they cause disease, how and why they behave, and how to best study these questions given past, current, and future technology.