Cyanophage N-1

The linear, double-stranded DNA genome 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 a GC-content of 35.4%. Of the 91 open reading frames (ORFs), only 33 show similarity to other known sequences. Remarkably, the genome of Cyanophage N1 encodes a functional CRISPR array, which has been suggested to protect the host against infection by competing viruses.^[1]

The optimal pH for viral adsorption to N. muscorum is 7.6–8.1. The rate of adsorption is reduced with increasing age of the host cells. The viral latent period is 7 hours, which is similar to cyanophages of the LPP-1 group. The burst size is 100 plaque-forming units per cell.^[6]

Host photosynthesis 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 by cyclic photophosphorylation and the use of carbohydrate stores; photosystem II activity is not required.^[7][8] Cyanophage N-1 infection of N. muscorum is associated with several changes in the host's carbon and nitrogen metabolism, including an increase in glucose-6-phosphate dehydrogenase enzyme concentration and a decrease in glutamine synthetase activity.^[9]

Sources

• Calendar R. The Bacteriophages (Oxford University Press; 2006) (ISBN 0195148509)
• Sarma TA. Handbook of Cyanobacteria (CRC Press; 2012) (ISBN 1466559411)