Bacteriophage levels and associated characteristics in selected temperate water systems

Abstract

Bacteriophages are studied in an effort to establish the viral safety of water as well as gather information as to what source of faecal pollution is dominant in a water system. The aim of this study was to determine bacteriophage levels and associated characteristics in selected temperate water systems. The methods used in this study were the double-agar–layer plaque assay, for enumeration of somatic coliphage and F-RNA phage levels. Transmission Electron Microscopy was used for characterisation and identification of somatic coliphages. RT-PCR was employed for identification of F-RNA phages. Physical parameter levels of the water systems were measured on site by multi-meter probes. Chemical parameter levels of the water systems were measured in the laboratory using a spectrophotometer. Six water systems in the North West Province of South Africa was studied. These water systems were: Mooi River, Harts River, Barberspan, Crocodile River, Marico River, and Schoonspruit River. Somatic coliphages were found at 34 of the 37 sites that were sampled in this study. The two sites that had no somatic coliphage detected in their water were both in the Crocodile River. The Delarey site in the Harts River was not analysed for phage levels. The highest somatic coliphage level detected in this study was 23 000.00 ± 989.95 pfp/100 mL in the Schoonspruit River. The highest F-RNA phage level recorded during the period of this study was 4 270.00 ± 11.84 pfp/100 mL in the Barberspan water system. The Marico River was the system least affected by environmental and species variables. Barberspan was the water system most severely impacted by F-RNA phage pollution sources. TEM images of plaques showed 3 different morphologies which could indicate a possible link between virion size of somatic coliphages and plaque morphology. However, definite statements regarding this is premature and requires further investigation. Human faecal pollution is entering Barberspan near the hotel sampling site as well as near the outflow of Barberspan into Leeupan sampling site. The physico-chemical parameter levels of the six water systems studied were all indicative of temperate water systems. Considering the bacteriophage and physicochemical parameter levels it is evident that all six water systems studied were being impacted by pollution from domestic and/or agricultural sources