The effect of temperature and various energy inhibitors on the formation of a complex between male cells and filamentous phage fd was studied by a novel filtration method. Centrifuged male cells were observed by electron microscopy to have lost the majority of pili and to produce complexes with fd only above 25 °C. After preincubation of the cells at 37 °C without addition of the phage, nearly half the level of complex formation observed at 37 °C was detected at 0 °C. Complex formation at various temperatures (0 to 37 °C) between cells preincubated at 37 °C and fd was at a minimum at about 20 °C. Several energy inhibitors and uncouplers drastically reduced complex formation at 37 °C, and also at 0 °C if the cells were briefly exposed to the reagents at the end of preincubation. Alteration of the cellular ATP concentration, either by shift-down of temperature or by the addition of the reagents, accompanied alteration in the ability of cells to form a complex with fd as well as alteration of the number of pili on the cell surface. In contrast to earlier reports, these results indicate that the complex formation between male cells and filamentous phage does not proceed either when pili disappear from the cell surface because of a decrease in the cellular energy level or when pili are removed by mechanical forces. The results also show that phage fd adsorption itself is not energy-dependent.


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