Constraints on Lateral Gene Transfer in Prokaryotes

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

Unlike typical eukaryotic taxa, Bacteria and Archaea are thought to evolve primarily through gene acquisition, that is, through the transfer of DNA between distantly related organisms. Such horizontal gene transfer occurs at high rates in many bacterial lineages, and virtually all prokaryotic genomes show a substantial fraction of recently acquired sequences. This project will extend our current understanding of the impact of horizontal gene transfer on the evolution of microbial genomes by examining constraints on DNA transfer between taxa. First, methods for detecting and quantifying recently acquired genetic material will be refined and extended by integrating identification of atypical genes (those not conforming to chromosome-wide sequence patterns) with detection of phylogenetic incongruencies. Second, these approaches will be used to develop a framework for understanding how and why the rate of successful gene transfer varies among species - that is, why some organisms are better DNA recipients; here organisms containing large amounts of low-value information may be more likely to accept horizontally transferred DNA since the incoming genes will be more likely to confer a benefit. Lastly, the probability of successful DNA transfer will be examined from a functional standpoint: that is, can chromosome structure impose a physical barrier to lateral transfer between distantly related organisms? Direct experimentation will test the roles of skewed, asymmetrically-distributed sequences in stalling replication forks, and computational analyses will determine if the strength of this barrier (the differences in these sets of sequences) increases with overall phylogenetic distance.