Recently Carrie Smith a talented undergrad student isolated two bacteriophages on E. coli from swine feces that have a very large genome size.
Currently, the top ten largest bacteriophage genomes within the ENA are
|Rank||Phage Name||Size kb||Accession|
|1||Bacillus phage G||497.513||JN638751|
|2||Aureococcus anophagefferens virus isolate BtV-01||370.92||KJ645900|
|3||Cronobacter phage vB_CsaM_GAP32||358.663||JN882285|
|4||Escherichia phage 121Q||348.532||KM507819|
|5||Escherichia phage PBECO 4||348.113||KC295538|
|6||Enterobacteria phage vB_KleM-RaK2||345.809||JQ513383|
|7||Pseudomonas phage 201phi2-1||316.674||EU197055|
|8||Pseudomonas phage PhiPA3||309.208||HQ630627|
|9||Pseudomonas phage OBP||284.757||JN627160|
|10||Pseudomonas phage Lu11||280.538||JQ768459|
The phage we isolated has a genome size of 348,043 bp and just misses out on being in the top five largest phage genomes. Whilst all the above phage genomes are larger than the vast majority of phage genomes, only Bacillus phage G makes it into the top 10 largest viral genomes. Even that is dwarfed by the giant Pandoravirus salinus (~ 2.4 Mb ) !
Preliminary analysis of the genome suggests the majority of predicted genes have no similarity to genes in current databases. However, a number of genomes have been identified that are homologues of host genes. These genes include gyrA, gryB and rpoD homologues.
Analysis of the gene encoding for the major capsid protein, suggests it is distantly related to other T4like T4_gp23