Role of F1F0-ATPase in the growth of Streptococcus mutans GS5

The role of F1F0-ATPase in Streptococcus mutans GS5 was investigated by iso lating a mutant (NTS1) defective in enzyme activity by homologous recombina tion with a plasmid encoding the 5' terminal fragment of the F1F0-ATPase be ta-subunit gene. The ATPase activity of NTS1 membranes was 49% that of GS5 membranes. The lag phase of the growth curve of NTS1 was longer than that f or GS5, and the lag phase of GS5 and NTS1 were prolonged by the addition of ionophore gramicidin D; at stationary phase, the turbidity of the NTS1 cul ture was less than that of the GS5 culture. These results suggest that S. m utans F1F0-ATPase contributes to the generation of a stoichiometric electro genic gradient effectively in the lag phase.