Factors which Influence the Enumeration of Bdellovibrio bacteriovorus in Sewage and River Water

S ummary . A double layer plating technique was used for counting Bdellovibrio bacteriovorus in river water and sewage samples. The optimum conditions for enumeration were provided by dilute media with 0.6 % of agar as the top layer, incubated for 6 days at 30° with Achromobacter sp. as the host. Pretreatment of samples affected counts: centrifugation and membrane filtration reduced the bdellovibrio count, homogenization increased it. Protozoa in sewage samples caused large plaques that greatly hindered counting and attempts to eliminate these plaques were unsuccessful. The highest counts in sewage samples averaged 900 cells/ml.