Revista internacional de contaminación ambiental
versão impressa ISSN 0188-4999
Bacteria that survive the pollutant mixing conditions of the upper basin of the Lerma river (CARL) require a specialized metabolism for survival. Under this postulation, sediment was taken from three sites of the CARL as a source of bacteria resistant to Cr+6. At the site identified as Lerma, greater variability of species was found in the group of selected bacteria that reduced Cr+6. In Tultepec, the highest population of Cr+6 reducing bacteria was isolated. Six strains with different morphological and biochemical characteristics were isolated from the sediments. These strains tolerated concentrations up to 1000 mg L-1 of Cr+6 in liquid media. Also they reduced Cr+6 to Cr+3 in percentages between 7 and 40, following 7 days, supplemented with 200 mg L-1 of Cr+6. The strains studied were Gram negative and showed a minimum inhibitory concentration greater than that found in other studies. The transformation capacity of each strain in descending order were: F, A, B, C, E and D. The kinetics of reduction of strain F showed the highest transformation of Cr+6 to Cr+3, obtaining a reduction of 33.59 % at 12 days. The biomass of strain F was not affected by the presence of Cr+6. It is important to note that the medium itself represented a reduction of Cr+6 (17.21 %). The use of the API-20E kit was helpful in determining some biochemical reactions of strains, however, this identification was not conclusive because it presented low percentages of similarity (83.1 to 90.7 %). These strains represent a potential of biotechnology for use in treatment systems to reduce Cr+6 to Cr+3, and even in trials of other heavy metals.
Palavras-chave : resistant bacteria; Cr+6; isolation; Cr+6-reduction; contaminated water body.