Little is known about the endemic bacteriophages of activated sludge. In this investigation 49 virus-host systems were studied by isolating co-occurring bacteria and bacteriophages from the aeration basin of a sewage treatment plant during 5 successive weeks. The phage titers were high and fluctuated during the time period. The occurrence of phage-sensitive and-resistant hosts did not depend on the presence or absence of phages. Several phage-host systems expressed variable plating efficiencies. In addition, phages with broad host ranges were observed. These results show that phages are an active part of this ecosystem and that they may exert selection pressure for phage resistance on their bacterial host populations.

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of total cellular proteins has been used to classify bacterial strains of the dispersed phase of activated sludge. The dominant bacterial populations are shown to be in dynamic change at species level while higher order taxons are more stable.

No abstract

No abstract