The membrane-bound H+-ATPase complex is essential for growth of Lactococcus lactis

The eight genes which encode the (F1F0) H+-ATPase in Lactococcus lactis sub sp, cremoris MG1363 were cloned and sequenced. The genes were organized in an operon with the gene order atpEBFNAGDC; i.e., the order of atpE and atpB is reversed with respect to the more typical bacterial organization. The d educed amino acid sequences of the corresponding H+-ATPase subunits showed significant homology with the subunits from other organisms. Results of Nor thern blot analysis showed a transcript at approximately 7 kb, which corres ponds to the size of the atp operon, The transcription initiation site was mapped by primer extension and coincided with a standard promoter sequence. In order to analyze the importance of the H+-ATPase for L, lactis physiolo gy, a mutant strain was constructed in which the original atp promoter on t he chromosome was replaced with an inducible nisin promoter. When grown on GM17 plates the resulting strain was completely dependent on the presence o f nisin for growth. These data demonstrate that the H+-ATPase is essential for growth oft. lactis under these conditions.