Technique for determining total bacterial virus counts in complex aqueous systems

A direct method is described for measuring bacteriophage concentrations in complex aqueous systems. Conditions for sample clarification, phage recognition, and recovery were optimized. In contrast to the plaque assay, this procedure permits quantitation of total numbers of phages independent of bacterial host. Also, the modifications increase the sensitivity of the sedimentation assay, permitting detection of particles at a minimum concentration of 10(4) per ml. Maximal total phage concentrations in the aqueous phase of sewage and activated sludge mixed liquor were 1.3 x 10(6) and 4.3 x 10(7) per ml, respectively.