Dr. Erik Zinser
See Also: Curriculum Vitae
Major Research Interests
We are interested in the process and consequence of adaptation in microorganisms. Natural selection impinges on the genetic variation (i.e. diversity) of microbial populations, and is a major driver in the generation of novel functions and niches in the microbial world. The primary focus of this group is the investigation of the relationships between physiology, ecology, and the forces of selection. We use a combination of field ecology and laboratory experimentation to explore adaptation in natural populations and in model microbes which can be manipulated genetically.
Adaptation in natural populations
While it is becoming clear that microbes are incredibly diverse, less clear is the ecological consequence of that genetic variation. A great challenge in microbial ecology is therefore to differentiate between “meaningful” variation (ecological determinants) and noise (neutral mutations). The system we use to explore this diversity is the unicellular cyanobacterium Prochlorococccus, which is the most abundant photosynthetic organism in the oceans, and as such is a major player in the Earth’s biogeochemical cycles. The Prochlorococcus lineage is highly diverse in its physiology and its genomic composition, and this diversity is reflected in the ecology. At least six distinct phylogenetic lineages are known for Prochlorococcus, and quantitative PCR analyses of their distributions in the Atlantic Ocean indicate that they occupy different niches in the water column. Our lab is interested in continuing to characterize the global distributions of these lineages (ecotypes), with particular emphasis on the Pacific Ocean. We are also using laboratory cultures of field isolates to investigate the underlying physiological and genetic bases of the niche partitioning observed in the oceans. Whole genome investigations with DNA microarrays and proteomics are underway, and recent advances in the development of a genetic system promise the ability to identify key adaptations that are responsible for the different physiologies and ecologies of the ecotypes.
Adaptation in experimental populations
Investigations of natural populations, such as those described above, give us a window into the past, and provide hypotheses about the adaptations and forces of selection that shaped the populations into their current state. To formally address hypotheses about the process of adaptation, however, one needs experimental (model) systems that provide well-defined conditions, experimental controls, and reproducibility to provide statistical confidence to the interpretations of the data. Our experimental system consists of starved batch cultures of Escherichia coli. Batch cultures of E. coli rapidly lose most of the population via starvation, but the remainder that survive compete for the nutrient resources released by the dying majority. This competition sets up natural selection, and mutants with the Growth Advantage in Stationary Phase (GASP) adaptations rapidly take over the population. These population takeovers occur successively throughout the period of starvation, and different survival strategies emerge: direct competition against the majority, and exploitation of novel niches that the majority do not occupy. Our laboratory focuses on the identification of the GASP mutations, their interactions with each other, and the forces of selection that allowed those GASP mutants to succeed. We are also interested in developing new model systems in photosynthetic organisms to investigate the process of selection in primary producers, both in isolation and in mixed cultures with heterotrophs that require the primary producers for nutrients.
Dr. Erik Zinser
Assistant Professor
Ph. D., 2001
Harvard University
M409 Walters Life Sciences
Knoxville, TN 37996-0845
Phone: 865-974-9283
Fax: 865-974-4007
Email: ezinser@utk.edu