Bacteriophages are the most abundant biological entities on earth, yet relatively few have been characterized. In this project, a novel bacteriophage was isolated from the environment, characterized, and compared with others in the databases. Mycobacterium smegmatis, a harmless soil bacterium, served as the host and facilitated the enrichment and recovery of mycobacteriophages. A single phage type was purified to homogeneity and named TiroTheta9 (TT9). Electron microscopy revealed that the phage particles have icosahedral heads 58 ± 2 nm in diameter and tails 174 ± 5 nm in length. The TT9 genomic DNA was purified and sequenced using 454 pyrosequencing technology. The 51,367 bp genome contains 87 genes that were identified using the gene prediction programs Glimmer and GeneMark. However, only 31 genes could be assigned functions based on BLAST analysis. Genome wide comparisons using the Phamerator program and BLAST revealed that TT9 is most closely related to members of the A4 subcluster of mycobacteriophages. Although the A4 subcluster phages have been isolated from geographically distinct locations, their genomic sequences are highly conserved. Comparative analysis of the subcluster reveals evidence of evolution through both vertical sequence divergence and horizontal gene transfer, as evidenced by the existence of three unique groups of integrases. These results have contributed to the rapidly expanding database of mycobacteriophage genomes; mining this rich source of genetic information should provide new insights into phage diversity and evolution.
Advisor(s) or Committee Chair
Dr. Rodney King
Schrader, Sarah, "The Isolation and Characterization of TiroTheta9, a Novel A4 Mycobacterium Phage" (2014). Honors College Capstone Experience/Thesis Projects. Paper 483.