Molybdate reduction to molybdenum blue by an Antarctic bacterium.

S A Ahmad,M Y Shukor,W P Mac Cormack,M A Syed,N A Shamaan

doi:10.1155/2013/871941

Abstract

A molybdenum-reducing bacterium from Antarctica has been isolated. The bacterium converts sodium molybdate or Mo6+ to molybdenum blue (Mo-blue). Electron donors such as glucose, sucrose, fructose, and lactose supported molybdate reduction. Ammonium sulphate was the best nitrogen source for molybdate reduction. Optimal conditions for molybdate reduction were between 30 and 50 mM molybdate, between 15 and 20°C, and initial pH between 6.5 and 7.5. The Mo-blue produced had a unique absorption spectrum with a peak maximum at 865 nm and a shoulder at 710 nm. Respiratory inhibitors such as antimycin A, sodium azide, potassium cyanide, and rotenone failed to inhibit the reducing activity. The Mo-reducing enzyme was partially purified using ion exchange and gel filtration chromatography. The partially purified enzyme showed optimal pH and temperature for activity at 6.0 and 20°C, respectively. Metal ions such as cadmium, chromium, copper, silver, lead, and mercury caused more than 95% inhibition of the molybdenum-reducing activity at 0.1 mM. The isolate was tentatively identified as Pseudomonas sp. strain DRY1 based on partial 16s rDNA molecular phylogenetic assessment and the Biolog microbial identification system. The characteristics of this strain would make it very useful in bioremediation works in the polar and temperate countries.

Highlights

Heavy metals pollution is a global problem
A low bootstrap value (
In contrast to previous results in EC 48 [16], our results suggest that the electron transport chain (ETC) of this bacterium is not the site of molybdate reduction

Summary

Introduction

Heavy metals pollution is a global problem. Remediation of heavy metals contaminated sites by bacteria is becoming more and more important. Traces of heavy metals due to anthropogenic sources have been found in soils in Antarctic and toxicity effects on fish in the surrounding area have been reported to occur [6,7,8]. Few studies have been carried out to study the possibility of microbes for the remediation of heavy metals in cold regions. Bioremediation using microbes may be the only cheap and workable technology to remediate metal contaminants in Antarctica and other cold regions. In this work we report on the isolation and characterization of a psychrotolerant bacterium with the ability to transform molybdenum to the insoluble molybdenum blue. This is the first molybdenum-reducing bacterium isolated from cold region. This bacterium could be used in future remediation works of molybdenum in Antarctica and cold climate regions

Experimental

Results

Discussions

Conclusion