Isolation and Identification of Two Novel Escherichia coli Bacteriophages and Their Application in Wastewater Treatment and Coliform's Phage Therapy

BACKGROUND: Phage therapy or use of lytic bacteriophages for eliminating bacterial populations has been developed for several aspects of human affairs such as medicine, agriculture and food industries. OBJECTIVES: The high load of coliforms of treated wastewater effluents that are discharged into the rivers or agricultural lands is a serious concern of the Iran Department of Environment and the reduction of coliforms using phages to overcome this problem is an asset. This research aimed to isolate and identify specific lytic coliphages and investigate their effects on native and standard Escherichia coli strains as well as coliform populations in municipal wastewater. MATERIALS AND METHODS: The wastewater sample was cultured on selective culture media to isolate a native coliform strain and characterized using molecular methods. River water was centrifuged and passed through a 0.45 μm filter and its lytic coliphages were enriched and purified against a native E. coli as well as a standard E. coli strain. Municipal wastewater was treated with isolated lytic coliphages and most probable number (MPN) reduction was examined. RESULTS: E. coli SBSWF27, which is a native strain of E. coli from Isfahan municipal wastewater treatment plant, was isolated and characterized. Also two novel bacteriophages related to Myoviridae and Podoviridae families of bacteriophages from Zayandehrood River (Isfahan, Iran) were isolated. These coliphages had lytic effects on E. coli PTCC1399 and E. coli SBSWF27 as coliform's index. The myovirus had a hexagonal head measuring 27.28 nm and a noncontractile tail measuring 204.5 × 13.63 nm. The podovirus had an oval head measuring 98 × 35 nm and a tail, 14 nm in diameter. The treatment of municipal sewage with the coliphage mixture resulted in a 22-fold decrease of the coliform's MPN from 2400 to 110 after two hours of incubation. CONCLUSIONS: This is the first report on isolation and identification of two novel lytic myovirus and podovirus from Zayandehrood River in Isfahan that had lytic effects on E. coli PTCC1399 and E. coli SBSWF27 strains as well as coliform's population of Isfahan municipal wastewater. We suggest that the use of these lytic coliphages for reduction of coliform's population in sewage could be considered as an effective and simple alternative for costly replacement of instruments and establishments of the old wastewater treatment plants.