Lateral gene transfer is a nearly ubiquitous influence on bacterial genome evolution, introducing a wide palette of novel genetic material the can facilitate adaptation; this is especially true in pathogens, where genomic islands have introduced metabolic functions allowing the adoption of the pathogenic lifestyle. While a large number of laterally transferred genes are recognized in recipient genomes, information regarding potential donor pools is limited. Since lateral gene transfer is such a powerful force for change, the nature of donor taxa - including their phylogenetic relationships and metabolic capabilities - provides a context for understanding the evolution of extant lineages, as well as insight into their evolutionary potential. Critically, there are several theoretical and empirical arguments for why donor taxa may not be chosen at random from all bacteria, but rather may be more closely related to the recipients. In this way, bacterial clades may form under the influence of gene transfer, and may not simply reflect the common ancestry of shared genes. We propose to identify the likely donor taxa for the recently-acquired gene pools of major bacterial clades. First, an artificial genome framework will be used to develop a robust method for utilizing and combining parametric methods for alien gene detection. Second, we will develop both gene cluster and genome segmentation methods for the identification of alien genes, using artificial genomes and parametric guidelines established above. These methods will identify groups of atypical genes that are similar to one another. The idea is that atypical genes with similar properties may have originated from the same source. Using these clusters of genes, we will ascertain their likely ancestry by extrapolating phylogenetic methods to infer the donor taxa for genes without homologues in the database. The assignment of donor taxa will be verified by a novel analysis of replication bias patterns, allowing us to correlate strand-bias patterns of alien genes with the signatures of the genomes in their donor's clades, which can be phylogenetically quite broad. This framework will allow us to test the hypothesis that gene transfer occurs more often between more closely related lineages. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM078092-03
Application #
7485794
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Eckstrand, Irene A
Project Start
2006-08-01
Project End
2010-07-31
Budget Start
2008-08-01
Budget End
2009-07-31
Support Year
3
Fiscal Year
2008
Total Cost
$162,600
Indirect Cost
Name
University of Pittsburgh
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Azad, Rajeev K; Li, Jing (2013) Interpreting genomic data via entropic dissection. Nucleic Acids Res 41:e23
Azad, Rajeev K; Lawrence, Jeffrey G (2012) Detecting laterally transferred genes. Methods Mol Biol 855:281-308
Retchless, Adam C; Lawrence, Jeffrey G (2012) Ecological adaptation in bacteria: speciation driven by codon selection. Mol Biol Evol 29:3669-83
Ricotta, Emily E; Wang, Nan; Cutler, Robin et al. (2011) Rapid divergence of two classes of Haemophilus ducreyi. J Bacteriol 193:2941-7
Azad, Rajeev K; Lawrence, Jeffrey G (2011) Towards more robust methods of alien gene detection. Nucleic Acids Res 39:e56
Retchless, Adam C; Lawrence, Jeffrey G (2011) Quantification of codon selection for comparative bacterial genomics. BMC Genomics 12:374
Retchless, Adam C; Lawrence, Jeffrey G (2010) Phylogenetic incongruence arising from fragmented speciation in enteric bacteria. Proc Natl Acad Sci U S A 107:11453-8
Lawrence, Jeffrey G; Retchless, Adam C (2009) The interplay of homologous recombination and horizontal gene transfer in bacterial speciation. Methods Mol Biol 532:29-53
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