Aeration sensitizes Streptococcus faecalis to hydroxyurea.

Hydroxyurea in up to 60 mM concentration did not inhibit growth or DNA synthesis in nonaerated cultures of Streptococcus faecalis ATCC 8043. In contrast, in cultures aerated by shaking already 1 mM hydroxyurea decreased the rate of net DNA synthesis and in higher concentrations of the drug the growth of the total cell mass also slowed down and the number of cells per chain increased from 1-2 to 10. The differential rate of DNA synthesis, but not the growth of the total cell mass, could be restored almost to the control level by adding thymidine to the medium. Thus there are at least two targets for hydroxyurea in the cells of S. faecalis grown in aerated cultures.