The Casjens laboratory is studying three rather different areas: (1) the genetic control of the assembly and function of virus particles, (2) modular evolution of bacteriophage genomes, and (3) genome structure, replication, and diversity of the Lyme disease causing bacteria, Borrelia burgdorferi, and its relationship to other bacterial genomes.
The work on virus assembly is concentrated on genetic and biochemical analysis of the proteins that are necessary for packaging a DNA molecule into bacteriophage P22 virions. Two of these are involved in recognizing the proper DNA for packaging, two build the particle itself, and another is required for DNA to enter the particles. We have also been involved in the sequencing of the genomes of several tailed-bacteriophages—P22, Sf6, L, Mu, N15, ES18, KO2, 9NA, Det7, and SPO1. These genomes are a rich source of diversity information as well as ideas for how bacteriophages evolve and interact with their hosts.
Our Borrelia burgdorferi work has shown that these bacteria are unique in that, unlike other bacteria, they have a linear chromosome with covalently closed hairpin ends, and they carry a very large number of linear and circular plasmid DNAs. Our current work is directed toward understanding the complete genomic nucleotide sequence of this pathogen and the extant genetic diversity of this species.