Effects Of High Atmospheric Co₂ Concentration On The Proliferation And Photoreactivation Of Cyanophage Pp

It has been predicted that atmospheric CO2 concentration will double by 2100. Much of the research effort has focused on the impacts of elevated atmospheric CO2 concentrations on marine algae but very little work has been done on freshwater algae, or on freshwater algal viruses.To study the impact of elevated atmospheric CO2 concentration on the infection of a freshwater cyanobacterium (wild Phormidium) by cyanophage PP and the photoreactivation ability for UV-B damaged cyanophage PP by wild Phormidium, wild Phormidium was cultured at concentrations of 370 and 740μL/L CO2.Some logarithmic phase host cells were collected and infected by cyanophage PP under two different CO2 concentration; the adsorption rate of cyanophage PP was measured by centrifugation method; the lysing cycle and burst size were confirmed by measuring the one-step growth curve. In addition, we examined the photoreactivation repair for the decayed cyanophage PP by host at 370 and 740μL/L CO2. The results show that increasing CO2 in airflow increased effectively the growth of host cyanobacteria. Furthermore, doubled CO2 enhanced the adsorption rates, burst sizes and the repair ratios of photoreactivation by 40.3%,32.6% and 78.4% respectively. However, doubled CO2 had no effect on the lysing cycle.In the medium and long-term culture experiments, some host cells were collected at 1,2,3,6 and 12 mo respectively under two different CO2 concentration. Experimental methods were conducted as previously described. The results are as followed:From 2mo later, the size of the host cell increased with the culture time at elevated CO2; Cell diameter increased 1.33 times than controls in 1 yr; In the elevated CO2 concentration, the adsorption rates, burst sizes of cyanophage PP, repair ratios of photoreactivation for decayed cyanophage PP by host all were significantly higher than controls, regardless of the culture time; The adsorption rate and burst size of cyanophage PP increased with the culture time at elevated CO2; In the elevated CO2 concentration, the repair ratios of photoreactivation by host also increased with the culture time between 1 and 3 mo, but gradually decreased and stabilized between 6 mo and 1 yr.Therefore, the elevated CO2 concentration could significantly influence the proliferation dynamics of cyanophage as well as the photoreactivation by host cyanobacteria, and our results may be helpful to estimate virus-mediated processes in future.