Aeration sensitizes Streptococcus faecalis to hydroxyurea.

The study compared growth and DNA synthesis in aerated and nonaerated cultures of S. faecalis. Cultures were either shaken or left static to control aeration. Hydroxyurea concentrations up to 60 mM were tested in nonaerated conditions. In aerated cultures, even 1 mM hydroxyurea affected DNA synthesis. Researchers measured net DNA synthesis rates using standard biochemical assays. They also monitored total cell mass and chain length as growth indicators. Thymidine was added to assess its restorative effect on DNA synthesis. The experimental design allowed for direct comparison of drug effects under different aeration levels.

Hydroxyurea up to 60 mM had no effect on nonaerated cultures. In aerated cultures, 1 mM hydroxyurea reduced DNA synthesis rates. Higher concentrations also slowed total cell mass growth. The number of cells per chain increased from 1-2 to 10 in aerated cultures. Thymidine restored DNA synthesis rates to near control levels in aerated cultures. This suggests at least two drug targets in aerated cells. The growth of total cell mass could not be restored by thymidine addition. These findings indicate differential drug effects based on aeration status.

The authors propose that aeration changes how hydroxyurea affects S. faecalis. They suggest at least two drug targets exist in aerated cultures. The differential response to thymidine implies separate mechanisms for DNA synthesis inhibition. The growth of total cell mass was not restored by thymidine addition. This indicates multiple pathways are affected by hydroxyurea in aerated conditions. The study highlights the importance of aeration in drug sensitivity. The findings suggest that environmental factors influence drug mechanisms. The authors conclude that further research is needed to identify these drug targets.