Physiological characterization of natural transformation in Acinetobacter calcoaceticus.

Acinetobacter calcoaceticus BD413 develops competence for natural transformation immediately after the start of the exponential growth-phase and remains competent up to e few hours into the stationary phase, after which competence gradually declines. The transformation frequencies obtained strongly depend on the kind of transforming DNA and the incubation time with DNA. Up to 25% of the cells in a culture can be transformed. DNA uptake in Acinetobacter does not display sequence specificity, is Mg(2+)-, Mn(2+)- or Ca(2+)-dependent and is uncoupler sensitive. The transforming DNA enters the cells in single-stranded form. These properties constitute a unique combination, not previously observed in other bacteria, and make A. caloaceticus ideally suited for detailed studies of the bioenergetics of DNA translocation.