Application of 2 microbioassays for evaluating the pollution present in the Xochimilco and Lerma-Santiago basins. / Aplicación de dos microbioensayos para evaluar la contaminación presente en las cuencas Xochimilco y Lerma-Santiago.

Pollution due to urban-agricultural and urban-industrial activities, on the enzymatic activity of two microorganisms was evaluated. The zones under study are located in the Caltongo "embarcadero", in Xochimilco, D.F., and the basin of Lerma-Santiago river, State of Mexico. Nine and ten stations were established, respectively. Samples of water and sediment were taken, in order to determine their pH, salinity, organic matter, as well as the toxic effect produced on Escherichia coli beta-galactosidase activity and on Bacillus cereus hydrogenase activity. Fecal coliforms and anionic detergents were quantified on the water samples. A correlation analysis was applied to results of chemical variables and microbiotest performed. In Xochimilco were found six stations over 50% of inhibition of the enzymatic activities evaluated, in Lerma-Santiago were only four stations. The correlation coefficient found was between -0.95 and 0.53. In general, the zones under study showed a pollution degree and toxic effect moderate, as well as a minimum correlation between chemical variables and the response of microorganisms used as indicators.