SURVIVAL OF CELLS AND DNA OF AEROMONAS-SALMONICIDA RELEASED INTO AQUATIC MICROCOSMS

The survival of the bacterial fish pathogen Aeromonas salmonicida, and persistence of its DNA, were monitored in aquatic microcosms using se lective culture and most probable number PCR. Bacterial cells and nake d DNA were released into natural non-sterile microcosms consisting of lake sediment overlayered with lake water. Two different types of surf ace sediment were used. One was sandy in character, taken from the sho reline whilst the other was a littoral loamy surface mud. Inoculated c ells and naked DNA became undetectable from water overlayers within 4 weeks of release. Colony counts of Aer. salmonicida declined below det ectable limits after 4 weeks in loamy sediment or 7 weeks in sandy sed iment; however, naked DNA and DNA from released cells remained detecta ble for more than 13 weeks.