DNA uptake in competent Streptococcus pneumoniae requires ATP and is regulated by cytoplasmic pH

DNA uptake in competent Streptococcus pneumoniae was strongly dependent on intracellular pH. Ionophore treatments that either acidified or alkalinized the cytoplasm reduced DNA transport. This indicates that the optimum pH for DNA uptake corresponds to the intracellular pH of competent bacteria which is 8.3 +/- 0.2. In addition, the ATP pool of the bacteria appeared to be a critical parameter in the process. The pattern of inhibition by arsenate, when the culture was treated at different steps of the competence cycle, suggested firstly, that a threshold ATP level was required to trigger transport and secondly, an ATP requirement for the process itself. This may indicate an ATP involvement in the activation of an uptake machinery functioning at the expense of ATP.