| Recent years, anti-bacteria effects of bacteriophages have been paid great attention by scientists. However, the investigators trying to apply bacteriophages to practical use all clearly realized that the anti- bacteria effects and applying range sometimes could be affected and limited by the narrow host range, one of the bacteriophage's characteristics. As anti- bacteria agents, a good application of bacteriophage must depend on the breakthrough in the process of recognition and lysis to host bacteriophages with special claim. In this study, Escherichia coli (E.coli) bacteriophages were screened from natural environment for artificial modification. In order to broaden the host ranges of phage at some degree, the changes of culture conditions have been designed for to induce the changes of biologic effects. Then the phage's configuration, growth curve, antigenic specificity, genosome constitutes and the bactericidal efficacy to samples from environmental had been observed before and after the artificial modification change. The evaluation about the feasibility for host ranges change with artificial technical were performed. Its mechanism and the possible of application for environmental improve have been described in the following.1.By using E. coli 285, E. coli 25922, E. coli BL21, E. coli JM109, E. coli HD5α, E. coli 10536 and E. coli 8099, five strains bacteriophages were isolated from sewage samples of Southwestern Hospital. They are bacteriophage of E. coli 285(bacteriophage XY-1); bacteriophage of E. coli 25922; bacteriophage of E. coli BL21; bacteriophage of E. coli JM109; bacteriophage of E. coli HD5α. Examination of their host ranges showed that all of these five strains of bacteriophages were lytic bacteriophages. Their lytic reaction was based on the form of one phage to its special host cell, without crossing-lysis phenomenon. All the phages have the bacteriolysis ability and the bacteriolysis titre to their host bacteria were higher than 109 pfu/ml.2. After incubating the phage with artificial technical, bacteriophage XY-1-M was obtained. Bacteriophage XY-1-M had the bacteriolysis ability, not only to its primitive corresponding host, but also for the other four strains of Escherichia coli. Moreover, the multi-host-lysis effect with high bacteriolysis titre could be preserved after 30-cycled culture.3. Treating the sewage water with bacteriophage XY-1-M, the germicidal test showed that its cleaning rate of E. coli in water samples from enviroment could reach 36.75-65.26%, and was obviously higher than the ordinary phage (P=0.000). The germicidal effect could be influenced by some factors, such as the amount of bacteriophage, environmental temperature, time of treatment and process of artificial incubation(P<0.01). 4. Comparing bacteriophage biological properties before and after artificial modification, a considerably high correlation in ultrastructure, nucleic acid type, antigenic specificity between bacteriophage XY-1 and bacteriophage f2 . Under electron microscope, the forms of three bacteriophages presented as tiny balls without distinct edges or corners, and with short-caudaed occasionally. All of their forms were inhomogenous in size and figure, with the diameter from 20 nm to 90 nm; The anti-serum K values of bacteriophage f2, bacteriophage XY-1, bacteriophage XY-1-M were 30.1,29.7or 41.5 respectively. A considerably higher correlation degree was founded between bacteriophage f2 and bacteriophage XY-1 (K value >0.96). But between bacteriophage f2 and bacteriophage XY-1-M, there was a low correlation degree (K value <0.45); Comparing bacteriophage XY-1-M with bacteriophage f2 and bacteriophage XY-1 , one-step-growth test showed that phage XY-1-M had a higher adsorption rate, shorter incubation period and a higher lytic efficacy.5. Analysis test for Nucleic acid revealed that bacteriophage XY-1 was a 6000 bp ,single-stranded RNA bacteriophage. Before and after artificial induction, the significant difference in RAPD-PCR and RT-PCR were founded, its indicated that the phage'...
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