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 en vironmental parameters [i.e, pH, selenium (Se) and salinity (electrica l conductivity, EC)] that simulated evaporation. Aeromonas veronii met abolized peptone and was active in volatilizing Se, principally as dim ethyl selenide (DMSe). Other volatile products produced included dimet hyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl dis elenide. The rate of Se volatilization correlated with the growth of A . veronii, with the highest levels of DMSe released during the exponen tial phase of growth. The C assimilated was primarily respired as CO, or incorporated into cell biomass with a small fraction used in the al kylation of Se. The maximum growth rate (mu(max)) for A. veronii was 0 .23 h(-1) at pH 7.94, 10 mu g Se l(-1), and EC of 3.9 dS m(-1) and dec reased to 0.06 h(-1) with increasing salt content (40.2 dS m(-1)), pH (8.53) and Se (500 mu gl(-1)). Salinity appeared to be the dominant in hibitory factor as observed by a decrease in growth rate and mass of c ells. 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 wat ers evaporate in holding facilities, salinity tends to increase having serious ecological effects on the growth of A. veronii.