title: Coevolution of bacteriophage PP01 and Escherichia coli O157:H7 in continuous culture.
abstract: The interaction between Escherichia coli O157:H7 and its specific bacteriophage PP01 was investigated in chemostat continuous culture. Following the addition of bacteriophage PP01, E. coli O157:H7 cell lysis was observed by over 4 orders of magnitude at a dilution rate of 0.876 h(-1) and by 3 orders of magnitude at a lower dilution rate (0.327 h(-1)). However, the appearance of a series of phage-resistant E. coli isolates, which showed a low efficiency of plating against bacteriophage PP01, led to an increase in the cell concentration in the culture. The colony shape, outer membrane protein expression, and lipopolysaccharide production of each escape mutant were compared. Cessation of major outer membrane protein OmpC production and alteration of lipopolysaccharide composition enabled E. coli O157:H7 to escape PP01 infection. One of the escape mutants of E. coli O157:H7 which formed a mucoid colony (Mu) on Luria-Bertani agar appeared 56 h postincubation at a dilution rate of 0.867 h(-1) and persisted until the end of the experiment (approximately 200 h). Mu mutant cells could coexist with bacteriophage PP01 in batch culture. Concentrations of the Mu cells and bacteriophage PP01 increased together. The appearance of mutant phage, which showed a different host range among the O157:H7 escape mutants than wild-type PP01, was also detected in the chemostat culture. Thus, coevolution of phage and E. coli O157:H7 proceeded as a mutual arms race in chemostat continuous culture.
authors.affiliation: Department of Bioengineering, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Mizoguchi
authors.forename: Masatomo
authors.initials: M
authors.lastname: Morita
authors.forename: Curt R
authors.initials: CR
authors.lastname: Fischer
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Yoichi
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Tanji
authors.forename: Hajime
authors.initials: H
authors.lastname: Unno
mesh_terms: D000818:Animals; D001433:Bacteriolysis; D003090:Coliphages / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D003470:Culture Media; D019453:Escherichia coli O157 / Q000235:genetics / Q000254:growth & development* / Q000821:virology*; D019143:Evolution, Molecular; D009154:Mutation
chemical_list: D003470:Culture Media