Abstract

ISLAS-ESPINOZA, Marina  and  BOJORQUEZ-AGUILAR, Rocío. Cr⁺⁶ reducing bacteria and its biotechnological potencial. Rev. Int. Contam. Ambient [online]. 2011, vol.27, n.3, pp.231-239. 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.

Keywords : resistant bacteria; Cr⁺⁶; isolation; Cr⁺⁶-reduction; contaminated water body.