Characterization of the chromium reduction activity of an endemic bacterium from the Atoyac river with potential use in water bioremediation

Abstract

Water pollution has become a major issue all over the world. One of the most devastating examples in Mexico is the Atoyac River, a victim mainly of the textile and automotive industries that produce contaminants such as phenolic compounds or heavy metals. Most of the contaminants in water bodies turn these ecosystems practically lifeless. However, unicellular organisms seem to be the only beings that thrive in polluted rivers. Bacteria are receiving more attention as model systems for bioremediation applications, given their availability and wide diversification in extreme ecosystems. This, in combination with the relative simplicity of the techniques for receiving genetic modifications, makes them ideal candidates as a source of biomolecules that might be used in the development of biosensors for monitoring the presence of pollutants in situ. Here, I propose a thesis whose main objective is to identify the possible mechanism, mainly the mediated by enzymes, of the hexavalent chromium reduction by an endemic bacterium (named Cr2.23a) isolated from the Atoyac River. In the characterization of this bacterial strain, it showed an optimal chromium reduction growing at pH of 8 and a temperature of 42°C. This reduction was localized on intracellular extracts, that would increase its efficiency by adding external electron donors such as glucose, lactose, sodium acetate, and NADPH. An API biochemical test identified this Cr 2.23a strain as two possible species: Klebsiella oxytoca and Raoultella planticola. To confirm these identification results, the 16s region of this strain was cloned and isolated. The molecular isolates were sent for sequencing to the Instituto Potosino de Investigación Científica y Tecnológica. These results will allow for the development of new strategies for water bioremediation and possibly a microbial biosensor for the detection of polluted bodies of water by heavy metals.