For complete details see Correa et al. (2012).
Following treatment, the tissue layer from each fragment was removed using an airbrush and 0.02 mm filtered viral-free 1_ PBS (pH 7.8). Coral and coral symbiont homogenates were collected in sterile tri-pour containers and pre-filtered with an 1-mm nucleopore filter (Whatman, Piscataway, NJ,USA). VLPs were concentrated from 27 ml of homogenate using ultracentrifugation of four-layer (1.2, 1.35, 1.5 and 1.7 g ml-1) cesium chloride density gradients (Vega Thurber et al., 2009). A gray band formed in the 1.2 g ml-1 density layer (Supplementary Figure 1a) and was harvested using an 18-gage needle and sterile syringe. Before and following a 0.22-mm Sterivex (Millipore, Billerica,MA, USA) filtration step (for details, see Vega Thurber et al. (2009)), this fraction was visualized using epifluorescence microscopy and SYBR Gold (Invitrogen, Carlsbad, CA, USA) staining (Noble and Fuhrman, 1998; Vega Thurber et al., 2009).
Related publications:
Correa, A.M., Welsh, R.M., and Vega Thurber, R.L. 2012. Unique nucleocytoplasmic dsDNA and +ssRNA viruses are associated with the dinoflagellate endosymbionts of corals. ISME J., 7(1): 13-27. doi:10.1038/ismej.2012.75