Prophage induction in marine Synechococcus
Filter each sample through a 0.2-µm filter to a volume of approximately 5 mL to remove most of the ambient viruses.
Add virus-free (0.02-µm filtered) water prepared from the same sample and reduce the volume a second time.
Return the retentate to its original volume by adding virus-free seawater, dividing into aliquots, and incubating with and without inducing agent.
Amend treated samples with the inducing agent mitomycin C at a concentration of 1 µg/mL or with the inducing agent of choice.
Employ the most probable number (MPN) method to enumerate the cyanophage population (Suttle and Chan 1994).
Prepare a one- to five-dilution series of the environmental or prophage induction treatment sample using 96-well microtiter plates (Costar, Corning Inc.).
Freshly dilute a susceptible Synechococcus host 1:10 and place in each well.
Prepare control plates similarly using sterile SN media in the first column of wells.
Prepare three replicate treatment and control plates from each site.
Incubate the plates until good growth of the host organism is evident (10–14 days).
Score wells as positive for virus if lysis of the host organism is evident as a well clearing.
Calculate viral abundance for each plate using an MPN program (Hurley and Roscoe 1983).
Evaluate treatment and control cyanophage and Synechococcus counts by paired t test between samples using Minitab statistical software.
Perform comparison of induction results and environmental parameters using linear regression and X2  analysis, also using Minitab.
