Metabolic changes associated with cyanophage N-1 infection of the cyanobacterium Nostoc muscorum

The development of cyanophage N-1 in the N₂-fixing cyanobacterium Nostoc muscorum is dependent on light. The redox state of thioredoxin m was altered in phage infected cells, with the proportion of reduced thioredoxin increasing during the eclipse period. In one step growth experiments, the specific activity of glucose-6-phosphate dehydrogenase increased transiently during the eclipse period, whereas that of glutamine synthetase increased towards the end of the eclipse period (2–4h after infection) then remained high until the end of the latent period (about 7 h after infection). The rate of respiratory O₂ uptake was maintained until the end of the latent period. In contrast, the specific activity of phosphoribulokinase and the rate of photosynthetic O₂ evolution began to decrease towards the end of the eclipse period and later than the level of extractable protein began to decrease. Nitrogenase activity remained high throughout the eclipse period then decreased rapidly after 5 h. The level of glutamine synthetase protein decreased in parallel with the decrease in total extractable protein, whereas the level of thioredoxin m protein decreased more slowly.