In situ monitoring of natural genetic transformation of Acinetobacter calcoaceticus BD413 in monoculture biofilms

摘要

Confocal laser scanning microscopy (CLSM) was used for the detection of natural genetic transformation in a defined pure culture Acinetobacter calcoaceticus BD413 biofilm, with the enhanced yellow fluorescent protein (EYFP) as a nonselective genetic marker. The effect of free DNA concentration and of exposure time to free DNA on transformation frequency was explored. Transformation studies indicated that Acinetobacter calcoaceticus BD413 cells exposed to as little as 0.1 ng free DNA/ml resulted in detectable transformation frequencies (1x10~(-4) transformed cells/recipient cell). Within 2 hours about 20percent of the biofilm cells expressed eyfp after exposure to 1 mug free DNA/ml. Microscopic analysis revealed a unique distribution of transformation frequencies in the biofilm. The highest frequencies were found near the substratum or near the biofilm/medium interface.