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Dynamics of cyanophage replication Brigden, Sean Malcolm

Abstract

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.

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