Characterization of Lactobacillus phages isolated from dairy products handled in Egyptian markets

Lactobacillus bacterial species isolated from their natural sources such as raw milk, whey, yogurts, and cheeses were identified as guided by their 16s rDNA molecular markers. Two specific phages were isolated from the identified Lactobacillus species. The isolated phages were designated as LPS1 and LPS2. The physical and chemical characteristics of both phages were studied. The results showed clear plaques with approximate diameters of 2.7 and 3.5 mm for LPS1 and LPS2, respectively. Morphological studies of the isolated phages as investigated by the transmission electron microscopy show that LPS1 and LPS2 belongs to Siphoviridae and Podoviridae, respectively. The physical properties show that these phages can tolerate UV, temperature up to 70°C and a wide range of pH degrees. The phage LPS1 show a higher tolerance towards the acidic pH in comparison to LPS2. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) of structural protein from LPS1 and LPS2 phages show that the protein's molecular weight of LPS1 phage is approximately 28 kDa, but that of LPS2 phage is approximately 31.5 kDa. Finally, the chemical properties of the isolated phages indicated that genetic material of both phages is dsDNA. The genome size of both isolated phages roughly was estimated from restriction fragments and is approximately 30:35 kbp.