SURVIVAL AND ACTIVITY OF LUX-MARKED AEROMONAS-SALMONICIDA IN SEAWATER

The fish pathogen Aeromonas salmonicida was chromosomally marked with genes encoding bacterial luciferase, luxAB, isolated from Vibro fische ri, resulting in constitutive luciferase production. During exponentia l growth in liquid batch culture, luminescence was directly proportion al to biomass concentration, and luminometry provided a lower detectio n limit of approximately 10(3) cells ml(-1), 1 order of magnitude more sensitive than enzyme-linked immunosorbent assay detection. In steril e seawater at 4 degrees C, lax-marked A. salmonicida entered a dormant , nonculturable state and population activity decreased rapidly. The a ctivity per viable cell, however, increased by day 4, indicating that a proportion of the population remained active and culturable. Putativ e dormant cells were not resuscitated after the addition of a range of substrates.