| Summary: | This study focuses on the infection characteristics (rate of adsorption, length of lytic
cycle and burst size) of two cyanomyoviruses, cyanophage S-PWM1 infecting cultures of
Synechococcus DC2 (Marine Cluster A) grown at a high irradiance (299 μmol quanta a m⁻² s⁻¹)
and low irradiance (19 μmol quanta m⁻² s⁻¹), and cyanophage S-PWM3 infecting Synechococcus
DC2 and SNC1 (Marine Cluster B) grown at high irradiance. The adsorption coefficients for SPWM1
adsorbing to DC2 under conditions of high and low light varied by a factor of 12 (1.26 x
10⁻⁸ and 1.03 x 10 ⁻⁹mL min SD = 1.88 x 10⁻⁹ and 3.75 x 10 ⁻¹⁰ respectively; n = 3). The
coefficients of adsorption for S-PWM3 adsorbing to DC2 and SNC1 were 9.04 x 10⁻⁹ and 9.72 x
10⁻⁹ m L min⁻¹ (SD = 4.33 x 10 ⁻¹⁰ and 3.34 x 10 ⁻¹⁰; n = 3) respectively. One-step growth
experiments indicated that for S-PWM1 infecting Synechococcus DC2 the length of the lytic
cycle was 17 h while the calculated burst size was 328 under high and 151 under low light,
respectively. For S-PWM3 infecting Synechococcus DC2, the length of the lytic cycle was 13 h
and the burst size was 135. For S-PWM3 infecting Synechococcus SNC1 the length of the lytic
cycle was 17 h and the burst size was 8. The results of this study show that light limitation
affects the rate of cyanophage adsorption and the burst size, and that there can be large
differences in burst sizes among different cyanophage-host systems. This implies that in nature
the physiological condition of the host will have a marked effect on phage replication, and that
these effects will be dependent on the composition of the cyanophage and cyanobacterial
communities. === Science, Faculty of === Botany, Department of === Graduate
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