Characterization of a molybdenum-reducing bacterium with the ability to degrade phenol, isolated in soils from egypt

Abstract

Polluted sites often contain both heavy metals and organic xenobiotic contaminants. This warrants the use of either a great number of bacterial degraders or bacteria having the ability to detoxify several toxicants simultaneously. In this research, the ability of a molybdenum-reducing (Mo-reducing) bacterium isolated from contaminated soil to decolorize various phenolics independent of Mo reduction was screened. Studies showed that this bacterium was able to grow on 4-nonylphenol and reduced molybdate to Mo-blue. The optimal condition for this activity was pH between 6.3 and 6.8 and temperature of 34 °C. Glucose proved to be the best electron donor for supporting molybdate reduction followed by galactose, fructose, and citrate in descending order. Other requirements included a phosphate concentration between 2.5 mM and 7.5 mM and a molybdate concentration between 20 and 30 mM. The absorption spectrum of the Mo-blue produced was similar to numerous previously described Mo-reducing bacteria, closely resembling a spectrum of the reduced phosphomolybdate. Mo reduction was inhibited by mercury (II), silver (I), copper (II), cadmium (II), and chromium (VI) at 2 ppm by 79.6%, 64.2%, 51.3%, 28.1%, and 25.0%, respectively. The biochemical analysis resulted in a tentative identification of the bacterium as Pseudomonas aeruginosa strain Amr-11. The ability of this bacterium to detoxify Mo and grow on nonylphenol makes this bacterium an important tool for bioremediation.