Related Experiment Videos
A method for the enumeration of male-specific bacteriophages in sewage
Abstract:
Male-specific bacteriophages adsorb to F-pili and thus can only infect male host strains. A method was developed for the selective enumeration of these phages, based on the observation that in sewage there are few phages capable of infecting F- -salmonellas--usually less than 10 pfu/ml. Using a male Salmonella strain, constructed by the introduction of the plasmid F'42 lac::Tn5 into Salmonella typhimurium phage type 3, plaque counts in secondary effluent were found to be in the range of 60-8200 pfu/ml. Practically all the phages detected had a host range restricted to male Salmonella or Escherichia coli strains, were resistant to chloroform and their infectivity was inhibited by RNase. Electron microscopy of lysates revealed phage particles that were morphologically identical to the male-specific single-strand RNA phages. Similar results were obtained with a strain of Salm. indiana carrying F'42 lac. A derivative of the Salm. typhimurium LT2 strain carrying an F-plasmid (F'42 lac fin P301) derepressed for fertility inhibition by the resident plasmid pSLT was equally sensitive to male-specific phages, but from sewage samples many other phages infecting F- E. coli but not F- Salmonella were isolated using this host strain.
Insights
Researchers developed a method to count male-specific bacteriophages in sewage. This technique utilizes a specific Salmonella strain to detect and quantify these phages, which infect only male bacteria.
Area of Science:
- Microbiology
- Virology
- Environmental Science
Background:
- Male-specific bacteriophages infect bacteria via F-pili, limiting their host range to male strains.
- Accurate enumeration of these phages in environmental samples like sewage is crucial for understanding their prevalence and ecological role.
Purpose of the Study:
- To develop and validate a selective method for enumerating male-specific bacteriophages in sewage.
- To characterize the phages detected in secondary effluent using a male Salmonella host strain.
Main Methods:
- Construction of a male Salmonella typhimurium strain carrying the F'42 lac::Tn5 plasmid for phage detection.
- Plating of secondary effluent samples on the developed male Salmonella host to determine plaque counts.
- Characterization of isolated phages based on host range, chloroform resistance, RNase sensitivity, and morphology via electron microscopy.
Main Results:
- The developed method enabled the detection of male-specific bacteriophages in secondary effluent at levels ranging from 60-8200 plaque-forming units/ml.
- The majority of detected phages exhibited host specificity for male Salmonella or Escherichia coli, resistance to chloroform, and RNase sensitivity.
- Electron microscopy confirmed the presence of morphologically consistent male-specific single-strand RNA phages.
Conclusions:
- A reliable method for the selective enumeration of male-specific bacteriophages in sewage has been established.
- The findings provide insights into the types and abundance of male-specific phages present in wastewater environments.
- This method can be applied to further studies on the ecology and potential applications of these bacteriophages.