Professor Department of Ecology and Evolution SUNY at Stony Brook State University of New York

Education : Lab Page : Research Interests :

Ph.D. 1971, University of Chicago Dykhuizen Lab Page As a student of Richard Lewontin, I decided that it should be possible to test evolutionary hypotheses experimentally. I picked the common colon bacterium, Escherichia coli, because it could grow in defined medium with a generation time of one or two hours and because the genetics and physiology were well known. With this short generation time, competition experiments of fifty generations can be done from Monday to Friday, allowing a free weekend. The bacteria are grown in a chemostat, a continuous flow device that maintains a constant environment, so that the fitness differences of two genotypes can be measured to an accuracy of less than 0.5%. At first, I thought of bacteria as little fruit flies. But they are not. They are very different creatures. My primary interest in experimental evolution is to understand the causes of natural selection: What conditions in the environment act upon what types of genetic variation to produce natural selection. I, with Tony Dean and Dan Hartl, have established a predictive theory of natural selection linking differences in enzyme activity to differences in fitness in a simple environment (publications 1 and 2). This theory can be extended to more complex environments (publication 4). We are currently extending this work to look at the long-term evolutionary dynamic of specialization. Sex in bacteria is very different from sex in animals or plants. Sex in bacteria has been separated from reproduction. Bacteria, rather than either being fully sexual or fully asexual, seem to have evolved an optimum level of sexuality or lateral gene transfer between lineages. Also, rather than mixing two lineages in equal proportions as animals and plants do, bacteria can transfer amounts as small as a few hundred bases to nearly half the chromosome. I showed that sexuality is important in E. coli (publications 3 and 5). I am now investigating the importance of lateral gene transfer in Borrelia burgdorferi, the cause of Lyme disease. B. burgdorferi has a very low rate of transfer of very small pieces of DNA, suggesting only the recombinants that have a selective advantage are seen in nature. I have an ongoing interest in species definitions and speciation in bacteria (publications 3, 6, and 10). Recently, I have started to work on the population genetics of infectious disease bacteria. We have shown that only four of the seventeen clones (serotypes) of the Lyme disease bacterium found in the Northeastern United States cause chronic Lyme disease (publication 9). This simplifies vaccine development. Evgeni Sokurenko and I have developed the idea that evolution is important during a chronic infection (publication 8). We are studying the adaptation of type 1 fimbrae in E. coli during bladder infections (publication 7 and curent work). I am interested in being able to find every mutational change in the genome during adaptation, either in a long-term chemostat experiment or in an infected animal. In this way we can track evolution happening.