Escherichia coli (E. coli) is used as an indicator microorganism in public health. The conventional way to detect E. coli requires several days to produce a result, because it requires incubation of cells. Therefore a rapid and sensitive detection method is needed. T4e-/GFP phage, characterized by suppression of lysozyme and fusion of GFP (green fluorescent protein) to its Soc (Small outer capsid), was constructed and it was shown to be able to detect E. coli K12 sensitively within several hours. However, because the host range of T4 phage to E. coli present in sewage water and sea water is narrow, this phage cannot be used to detect E. coli in environmental water. Two phages named IP008 and IP052, which have a broad host range to E. coli present in sewage influent, were screened from sewage influent. To use these phages as a tool for detection of E. coli, gfp was inserted into gene-e which encodes a lytic enzyme, and the lytic-activity-suppressed phages were constructed (IP008e- and IP052e-). However, fluorescent intensity of E. coli cells infected with IP008e- and IP052e- was not enough for visualization of the cell. Therefore, in addition to the insertion of gfp to gene-e, fusion of GFP to SOC of IP008e- and IP052e- was conducted to produce IP008e-/GFP and IP052e-/GFP. E. coli cells infected with IP008e-/GFP and IP052e-/GFP showed much stronger fluorescence intensity than E. coli cells infected by IP008e- and IP052e-. It is anticipated that using these GFP-labeled phages, broad range of E. coli present in sewage influent water can be detected rapidly.
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