A freshwater cyanophage whose genome indicates close relationships to photosynthetic marine cyanomyophages

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  • Bacteriophage S-CRM01 has been isolated from a freshwater strain of Synechococcus and shown to be present in the upper Klamath River valley in northern California and Oregon. The genome of this lytic T4-like phage has a 178,563 bp circular genetic map with 297 predicted protein-coding genes and 33 tRNA genes that represent all 20 amino acid specificities. Analyses based on gene sequence and gene content indicate a close phylogenetic relationship to the “photosynthetic” marine cyanomyophages infecting Synechococcus and Prochlorococcus. Such relatedness suggests that freshwater and marine phages can draw on a common gene pool. The genome can be considered as being comprised of three regions. Region 1 is populated predominantly with structural genes, recognized as such by homology to other T4-like phages and by identification in a proteomic analysis of purified virions. Region 2 contains most of the genes with roles in replication, recombination, nucleotide metabolism and regulation of gene expression, as well as 5 of the 6 signature genes of the photosynthetic cyanomyophages (hli03, hsp20, mazG, phoH and psbA; cobS is present in Region 3). Much of Regions 1 and 2 are syntenous with marine cyanomyophage genomes, except that a segment encompassing Region 2 is inverted. Region 3 contains a high proportion (85%) of genes that are unique to S-CRM01, as well as most of the tRNA genes. Regions 1 and 2 contain many predicted late promoters, with a combination of CTAAATA and ATAAATA core sequences. Two predicted genes that are unusual in phage genomes are homologs of cellular spoT and nusG.
  • Keywords: Myoviridae, Phage tRNA, T4-like phage, Cyanomyophage, Freshwater phage, spoT, Klamath River, nusG
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  • Dreher, T. W., Brown, N., Bozarth, C. S., Schwartz, A. D., Riscoe, E., Thrash, C., Bennett, S. E., Tzeng, S.-C. and Maier, C. S. (2011), A freshwater cyanophage whose genome indicates close relationships to photosynthetic marine cyanomyophages. Environmental Microbiology, 13: 1858–1874. doi:10.1111/j.1462-2920.2011.02502.x
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  • 13
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  • 7
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  • The OSU mass spectrometry facility and services core is supported in part by NIH/NIEHS grant P30 ES000210. This work was supported by Oregon Sea Grant award NA060AR4170010 and by Oregon State University Agricultural Experiment Station.
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