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 ) .
