Isolation of 18 Novel Mycobacteriophages and Genomic Analyses of Krueger and Phrappuccino
Dr. Aaron Best and Dr. Joseph Stukey
Eighteen new mycobacteriophages were isolated from soil samples collected around the state of Michigan and parts of the United States. All phages were capable of infecting Mycobacterium smegmatis and were isolated through either enrichment or direct plating at 25°C. A variety of plaque morphologies were produced based on size, shape, and clarity; both lytic and temperate phages appear represented in this collection. Two mycobacteriophages, Krueger and Phrappuccino, were chosen for complete genome sequencing and comparative genomic analyses. The predominant plaque produced by Krueger at 32°C was circular and 2 mm in diameter. The predominant plaque produced by Phrappuccino at 32°C was 1 mm in diameter, and took 48 hours to appear. Complete genome sequence for Krueger revealed relationships to members of the novel Subcluster K6, while Phrappuccino was not closely related to any known phage and is currently classified as a Singleton. The genome of Krueger is 60.3 Kb, 66.5% GC, and contains 101 genes, including 1 tRNA(Lys-TTT) gene; the genome of Phrappuccino is 136.3 Kb, 67.4% GC, and contains 200 genes. While Phrappuccino is a Singleton, there is strong evidence at the morphological (Myoviridae) and genomic levels for a relationship to Cluster C phages. Despite this relationship, Phrappuccino does not carry any tRNA genes. Forty (39.6%) and thirty-six (18%) protein coding genes were assigned functions in Krueger and Phrappuccino, respectively, based on comparative analyses. A detailed analysis of the complete genome sequences and comparison with sequenced mycobacteriophages is the subject of the second semester of this yearlong course and is presented.
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