Figure 5.

The P1 genome and composition of the virion. (A): Genome map of phage P1 summarizing P1 morphogenesis genes. The size of the boxes indicates the size of each ORF, with genes encoded on the plus and minus strands staggered up and down, respectively. Genes colored black are involved in phage morphogenesis, based on the work presented here or in previous studies [10]. Products of genes outlined in red were detected in LC-MS/MS above the two-peptide threshold. Genes with bold labels were determined to be essential for morphogenesis by construction of single-gene deletions. The deletion of gray genes produced no antirestriction phenotype and no apparent defect in plating, thus these genes are considered non-essential with unknown function. Gene labels are color-coded to indicate their predicted location in the virion (panel B), with blue indicating the head, magenta the tail, and green the baseplate. (B): A schematic of the P1 virion, partitioned into three components of the head, tail, and baseplate (including tail fibers). Structural proteins are assigned to each area based on their predicted roles; color coding corresponds to the coding of gene labels in panel A. Sit is listed in both the tail and baseplate as its role as tape measure protein makes it a part of both components. Proteins PmgA, UpfC, gp5, and gp26 are marked with an asterisk as these are predicted to be part of the virion based on bioinformatics but were not detected by LC-MS/MS. Gene iddB omitted for simplicity.