TABLE 2.

Statistical ANOVA of four different treatments (freezing, fixation, heating, and addition of detergent) for all viruses tested together or separated into two groups (phytoplankton viruses and heterotrophic bacteriophages)a

Virus included in statistical analysisFactor treatmentLevelsLog
CountsGFLSSC
All virusesb2 (phytoplankton viruses and heterotrophic phages)********
Fixationc2 (yes/no)******
Heating at 80°Cd2 (yes/no)*********
Liquid nitrogen (N2)2 (yes/no)
Triton additione2 (yes/no)
Group vs 80°CInteraction*****
Group vs fixationInteraction****
80°C vs fixationInteraction**
Virus type in group13*********
Virus type vs fixationInteraction******
Virus type vs 80°CInteraction***
Phytoplankton virusesFixationc2 (yes/no)***
Heating at 80°Cd2 (yes/no)******
Liquid nitrogen (N2)2 (yes/no)**
Triton additione2 (yes/no)
Virus type vs 80°CInteraction
Virus type vs fixationInteraction***
Virus type vs N2Interaction***
80°C vs fixationInteraction
80°C vs N2Interaction
Heterotrophic bacteriophagesFixationc2 (yes/no)***
Heating at 80°Cd2 (yes/no)******
Liquid nitrogen (N2)2 (yes/no)
Triton additione2 (yes/no)
Virus type vs 80°CInteraction***
Virus type vs fixationInteraction***
80°C vs fixationInteraction*
  • a A four- or five-way ANOVA with interaction terms and two levels for each treatment was used. The treatments that were found to significantly affect total viral counts, GFL, or SSC of the stained virus particles are indicated by asterisks: *, P < 0.05; **, P < 0.01; and ***, P < 0.001. SYBR Green I was used as nucleic acid-specific dye (diluted ×10−5 of the commercial stock).

  • b Virus types were a nested factor within the virus groups.

  • c Final glutaraldehyde concentration of 0.05%.

  • d Incubation at 80°C for 10 min, followed by cooling for 5 min or incubation at 20°C for 15 min.

  • e Final Triton X-100 concentration of 0.1% (vol/vol).