MOLECULAR-BASIS OF TBE OPTOCHIN-SENSITIVE PHENOTYPE OF PNEUMOCOCCUS -CHARACTERIZATION OF THE GENES ENCODING THE F-0 COMPLEX OF THE STREPTOCOCCUS-PNEUMONIAE AND STREPTOCOCCUS-ORALIS H-ATPASES()

The gene responsible for the optochin-sensitive (Opt(S)) phenotype of Streptococcus pneumoniae has been characterized. Sequence comparisons indicated that the genes involved encoded the subunits of the F-0 comp lex of an H+-ATPase. Sequence analysis and transformation experiments showed that the atpC gene is responsible for the optochin-sensitive re sistant (Opt(S)/Opt(R)) phenotype. Our results also show that natural as well as laboratory Opt(R) isolates have arisen by point mutations t hat produce different amino acid changes at positions 48, 49 or 50 of the ATPase c subunit. The nucleotide sequence of the F-0 complex of th e Streptococcus oralis ATPase has also been determined. In addition, c omparison of the sequence of the atpCAB genes of S. pneumoniae R6 (Opt (S)) and M222 (an Opt(R) strain produced by interspecies recombination between pneumococcus and S. oralis), and S. oralis revealed that, in M222, an interchange of atpC and atpA had occurred. We also demonstrat e that optochin specifically inhibited the membrane-bound ATPase activ ity of the S. pneumoniae wild-type (Opt(S)) strains, and found a 100-f old difference between Opt(S) and Opt(R) strains, both in growth inhib ition and in membrane ATPase resistance.