The Relationship Between Lateral Gene Transfer and Patterns of Diversification of Sulfate-Reducing Microorganisms

University Of Washington, Seattle WA

Investigators

Abstract

Drs. David A. Stahl and Jesse G. Dillon of the University of Washington have been awarded a grant to study the evolutionary histories of certain microorganisms, and how they develop new metabolic capabilities. Stahl and Dillon will focus their research on microbes that respire ("breathe") sulfate rather than oxygen, asking how they acquired this ability. Earlier studies have shown that exchange of genetic information between phylogenetically widely separated microbial groups has contributed to the evolution of sulfate-respiring microbes. However, the role this process (horizontal gene transfer) has played in their speciation and diversification is unknown. These investigators will use molecular and culture-based techniques, in combination with high-speed sorting of single cells using flow cytometry technology, to better resolve the contribution of horizontal gene transfer to the speciation process. It is known that organisms that live by sulfate respiration were present on earth at least as early as 3.5 billion years ago. Thus, they represent one of the earliest types of life on earth. Today they play a central role in the sulfur cycle, a key biogeochemical process on our planet. They are widely distributed in the environment and contribute to the biodegradation of organic matter in virtually all habitats lacking oxygen. For example, they can be responsible for one half of the total carbon degradation occurring in near-shore marine sediments. Although sulfate respiring microorganisms are central participants in global sulfur and carbon cycles, little is known about how this mode of living originated and how it has diversified within and among different earth habitats. The study of how horizontal gene transfer has influenced the distribution of sulfate respiring organisms will contribute to a better understanding of the microbial speciation process, and also address a more fundamental question of the origin of our planet's biogeochemical cycles.