DIFFERENTIAL EFFECT OF TETRAZOLIUM DYES UPON BACTERIOPHAGE PLAQUE-ASSAY TITERS

This study examined whether the practice of incorporating either tetra zolium red or tetrazolium violet dye into plaque assay medium deleteri ously influences plaque assay titers. Representative members of six di fferent virus families were studied: Cystoviridae (phi 6), Leviviridae (MS2), Microviridae (phi X174), Myoviridae (T2), Podoviridae (P22), a nd Siphoviridae (Denver, T1, and VD13). Each of the members of the Pod oviridae and Siphoviridae families appeared to be suppressed by either one or both dyes at a 300 mu g/ml concentration. The chosen represent atives of the other bacteriophage families were not suppressed by eith er dye at a 300-mu g/ml! concentration. Subsequent trials revealed no suppression of Podoviridae or Siphoviridae plaque assay titers when me mbers of these virus families were tested with the same two dyes at th e lower concentrations of 150 and 50 mu g/ml. Interestingly, the bacte riophage families whose members were affected by the dyes have additio nal commonality in that they are the two bacteriophage families whose members possess both double-stranded DNA genomes and noncontractile ta ils.