Four environmental bacterial isolates including Aeromonas hydrophila MP-3, A. salmonicida MP-4, Vibrio vulnificus MP-2 and V. cholerae MP-1 isolated from sediment and water of Mai Po Nature Reserve of Hong Kong were examined for their responses to temperature, pH and salinity under laboratory conditions in this study. V. cholerae MP-1 was found to resist vibriostatic agent O/129 at concentration of 10 μg/ml. In addition, bacterial growth under test conditions was measured and the results were fitted into the Gompertz model to obtain important parameters related to bacterial growth, lag time (λ), specific growth rate (μm), and maximum biomass (A) for comparison. V. cholerae MP-1 did not show any apparent growth at 15°C, but was adapted to a much wider environmental pH from 5.2 to 9.2 for growth while V. vulnificus MP-2 was more sensitive to pH changes yielding the highest biomass at pH 6.2. A. salmonicida MP-4 was surprisingly tolerant to salinity as high as 60.0‰ NaCl and grew almost equally well as under conditions of other treatments. All four bacterial isolates showed a wide spectrum of plasticity to the environmental conditions and they pose a potential threat to public health and animal health.