FIG. 1.

Northern blot analysis of empA expression in LB20 and NSSM. (A) V. anguillarum strains NB10 and M93Sm were grown overnight in LB20 to stationary phase. Cells were washed twice in NSS and resuspended under the experimental conditions at 2 × 10⁹ CFU/ml. Cells were incubated (27°C) with shaking. Samples (1 ml) were taken at 0, 15, 30, 60, 90, 120, and 180 min. Total RNA was isolated and separated on a formaldehyde agarose gel (5 μg of RNA/sample). RNA was transferred from the gel to a nylon membrane and probed with a DIG-dUTP-labeled empA probe for 16 h at 51°C. Panel B shows the RNA gel from panel A stained with ethidium bromide to demonstrate equal loading of all samples. (C) mRNA half-life for empA was determined in M93Sm cells incubated in NSSM for 3 h. Rifampin was added to the cell suspension, and cell samples (1 ml) were taken at 0, 2, 4, 6, 8, and 10 min. Total RNA was prepared and analyzed as described above for panel A.