Spot-on-lawn (halo) assay for screening enrichment cultures and isolates for viruses
Gelrite plates are preincubated ca.
10 min at 80˚C to dry.
10 mL of Sulfolobus medium with ca. 0.2 % (w/v) Gelrite is boiled to dissolve the Gelrite.
This “softlayer” is allowed to cool slightly (to ca. 80˚C).
Approximately 3 mL of softlayer are added to ca. 0.2 mL of exponentially growing host cells, generally Sulfolobus solfataricus, and spread on a plate by swirling.
After the Gelrite solidifies, 1–2 µL of culture or supernatant to be screened is spotted on the plate.
For a positive control, 1 µL of a 0.01% (v/v) Triton X-100 solution is spotted.
Plates are incubated as above for 2–3 d and plates examined for clearing around spots (Fig. 1D in guidelines).
