ACINETOBACTER-CALCOACETICUS LIBERATES CHROMOSOMAL DNA DURING INDUCTION OF COMPETENCE BY CELL-LYSIS

A transformation assay was used to assay the amount of DNA present in the extracellular medium of a growing culture of Acinetobacter calcoac eticus. It was observed that small amounts of DNA were liberated durin g the entire exponential growth phase in a batch culture. Release of D NA could be fully accounted for by lysis of cells. Lysis was quantifie d via simultaneous measurement of beta-galactosidase activity of cells and supernatant, with a strain that contained a plasmid (pAPA100) wit h lacZ under control of a constitutive beta-lactamase promoter. In con clusion, no evidence could be obtained indicating that Acinetobacter c alcoaceticus actively excretes DNA, to be used for DNA exchange.