Jumbo Phages

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