The impact of horizontal gene transfers on prokaryotic genome evolution

Date of Completion

January 2007


Biology, Genetics|Biology, Bioinformatics




With the advent of whole genome sequencing, it became apparent that horizontal transfer gene (HGT) is not limited to a few specific sets of genes nor does it only occur between a few select species. It is now believed that such gene transfers have played a predominant role for evolution of life, especially for prokaryotic species. Over the course of my graduate years, tremendous progress has been made in the study of the evolution of life. Fully sequenced genomes has allowed access to the dynamics of genome evolution in unprecedented ways and has led to surprising new discoveries that are redefining our comprehension of the evolution. ^ The main topic of my doctoral thesis focuses on studying genome evolution as a whole with emphasis on how gene transfers are shaping genomes over time. By looking at specific gene histories, genomic comparisons of closely related species and the complete gene family repertoire of the bacterial domain, I have further advanced our knowledge of the mechanisms and evolutionary forces acting on genomes. I have found that not only are gene transfers important for adaptation and colonization of new niches but may also contribute to the creation of new protein fold in nature. Additionally, genomes must now be seen as an ever changing collection of genes and our definition of prokaryotic species should include the environmental components, i.e. microorganisms living in the same environment have access to a shared pool of genetic material. ^ We are now entering an exciting new phase in the genomic era where studies of individual genomes are giving way to the exploration of communal meta-genomes and pan-genomes. This thesis offers a view of our state of knowledge of genome evolution and provides glimpses of what is lying ahead in term of future research on the evolution of life. ^