الفهرس 
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Abstract
The present study was carried out in the laboratory of Agricultural Microbiology Department, Faculty of Agriculture, Zagazig University, Egypt. The present study aimed to investigate the occurrence of some bacteria and their phages in some water sources. These bacteria included total bacterial count, E. coli, total coliform, Aeromonas, Enterobacter, Salmonella and Shigella. Six isolates were chosen based on their common colony characteristics in the different locations, and were subjected to biochemical identification. Three of the isolates were Aeromonas spp., and the others were Aeromonas salmonicida subsp. pectinolytica, Enterobacter aerogenes and Enterobacter cloacae subsp. dissolvens. Fifteen antibiotics were tested against eleven bacterial isolates, where there was a wide variation in the sensitivity of the isolates to the same antibiotic, and also in the effect of different antibiotics on the same isolate. Enterobacter cloacae subsp. dissolvens was one of the most resistant isolates, and Amoxicillin was the most effective against most isolates. Four phages were isolated and subjected for characterization. Phage host range was performed against the 64 isolates, where the host was E. cloacae subsp. dissolvens for three of them, while E. aerogenes was the host for the fourth one. The phages were examined by electron microscope, where phages Ec02 and Ec03 were belonging to family Myoviridae, and phages Ec01 and Ea01 were belonging to family Siphoviridae. The One-step growth curve experiments determined the latent periods as 20min for Ea01, and 15 min for the others, and phage burst size ranged between 94 and 325 PFU/ infected cell. As for the time required to achieve 50% adsorption, phage Ec02 was the fastest one reaching more than 50% after 9 min. The effect of temperature revealed that Ec03 was the most stable (50min at 70°C). Stability for different pH levels and the sensitivity for UV were studied, where phage Ec03 was the most resistant to UV irradiation. Storage experiment showed that 4°C was better than -20°C.