| Cyanophage N-1 | |
|---|---|
| Virus classification | |
| Group: | Group I(dsDNA) |
| Order: | |
| Family: | |
| Genus: | Cyanomyovirus (proposed) |
| Species: | Cyanophage N-1 |
Cyanophage N-1 is amyovirusbacteriophage that infects freshwater filamentouscyanobacteria of theNostocgenus.[1] The virus was first isolated by Kenneth Adolph and Robert Haselkorn in 1971 in the US, from thenitrogen-fixing cyanobacterium,Nostoc muscorum.[2][3] N-1 is closely related to cyanophage A-1, but only distantly to othercyanophages of freshwater or marine origin.[1]
The virus has a polyhedral head with a diameter of around 61 nm. The contractile tail is 100 nm long, and is attached to the head via a tail capital. The neck region bears fibres. The mature virus particle contains at least 19 proteins.[2][4][5]
The linear, double-stranded DNAgenome is 64,960 base pairs in length – only half the size of most phages with contractile tails, which typically fall in the range 161–231 kb. It has aGC-content of 35.4%. Of the 91open reading frames (ORFs), only 33 show similarity to other known sequences. Remarkably, the genome of Cyanophage N1 encodes a functionalCRISPR array, which has been suggested to protect the host against infection by competing viruses.[1]
The optimal pH forviral adsorption toN. muscorum is 7.6–8.1. The rate of adsorption is reduced with increasing age of the host cells. The virallatent period is 7 hours, which is similar to cyanophages of theLPP-1 group. The burst size is 100 plaque-forming units per cell.[6]
Hostphotosynthesis is required for the virus to replicate, with photosynthesis being required throughout the life cycle, rather than at any particular point. Viral replication is powered bycyclic photophosphorylation and the use ofcarbohydrate stores;photosystem II activity is not required.[7][8] Cyanophage N-1 infection ofN. muscorum is associated with several changes in the host's carbon and nitrogen metabolism, including an increase inglucose-6-phosphate dehydrogenase enzyme concentration and a decrease inglutamine synthetase activity.[9]
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