Influence of pH,salinity, and selenium on the growth of Aeromonas veronii in evaporation agricultural drainage water

Aeromonas veronii was isolated from seleniferous agricultural drainage water and characterized in terms of growth kinetics under changing environmental parameters i.e. pH, selenium (Se) and salinity (electrical conductivity, EC)] that simulated evaporation. Aeromonas veronii metabolized peptone and was active in volatilizing Se, principally as dimethyl selenide (DMSe). Other volatile products produced included dimethyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl diselenide. The rate of Se volatilization correlated with the growth of A. veronii, with the highest levels of DMSe released during the exponential phase of growth. The C assimilated was primarily respired as CO₂ or incorporated into cell biomass with a small fraction used in the alkylation of Se. The maximum growth rate (μ_max) for A. veronii was 0.23 h⁻¹ at pH 7.94, 10 μg Se 1⁻¹, and EC of 3.9 dS m⁻¹ and decreased to 0.06 h⁻¹ with increasing salt content (40.2 dS m⁻¹), pH (8.53) and Se (500 μg l⁻¹). Salinity appeared to be the dominant inhibitory factor as observed by a decrease in growth rate and mass of cells. The range in salt content that was most inhibitory to the growth rate of A. veronii was from EC 11.7 to 40.2 dS m⁻¹. As drainage waters evaporate in holding facilities, salinity tends to increase having serious ecological effects on the growth of A. veronii.