Pollution as a result of anthropogenic activities is a severe global issue. These activities including inappropriate disposal, industrial and prospecting activities and unnecessary use of agricultural chemicals have triggered international initiatives to eliminate these contaminants. In this work we screen the ability of a molybdenum-reducing bacterium isolated from contaminated soil to grow and reduce molybdenum on various detergents. The bacterium was able to grow on SDS as a carbon source although the compound did not support molybdenum reduction. The bacterium reduces molybdate to Mo-blue optimally between pH 5.8 and 6.3 and between 25 and 34 o C. Glucose was the best electron donor for supporting molybdate reduction followed by sucrose, D-mannitol, D-sorbitol, lactose, salicin, trehalose, maltose and myo-Inositol in descending order. Other requirements include a phosphate concentration between 5.0 and 7.5 mM and a molybdate concentration between 5 and 20 mM. The absorption spectrum of the Mo-blue produced was similar to previous Mo-reducing bacterium, and closely resembles a reduced phosphomolybdate. Molybdenum reduction was inhibited by mercury (ii), silver (i) and copper (ii) at 2 ppm by 62.1, 33.9 and 33.6%, respectively. Biochemical analysis resulted in a tentative identification of the bacterium as Klebsiella oxytoca strain Aft-7. The ability of this bacterium to detoxify molybdenum and degrade detergent makes this bacterium an important tool for bioremediation.

Bioremediation of pollutants including heavy metals and xenobiotics is an economic and environmentally friendly process. A novel molybdenum-reducing bacterium with the ability to utilize the pesticide glyphosate as a carbon source is reported. The characterization works were carried out utilizing bacterial resting cells in a microplate format. The bacterium reduces molybdate to Mo-blue optimally between pH 6.3 and 6.8 and at 34 o C. Glucose was the best electron donor for supporting molybdate reduction followed by lactose, maltose, melibiose, raffinose, d-mannitol, d-xylose, l-rhamnose, l-arabinose, dulcitol, myo-inositol and glycerol in descending order. Other requirements include a phosphate concentration at 5.0 mM and a molybdate concentration between 20 and 30 mM. The molybdenum blue exhibited an absorption spectrum resembling a reduced phosphomolybdate. Molybdenum reduction was inhibited by mercury, silver, cadmium and copper at 2 ppm by 45.5, 26.0, 18.5 and 16.3%, respectively. Biochemical analysis identified the bacterium as Klebsiella oxytoca strain Saw-5. To conclude, the capacity of this bacterium to reduce molybdenum into a less toxic form and to grow on glyphosate is novel and makes the bacterium an important instrument for bioremediation of these pollutants.

Acetylcholinesterase (AChE) generally known to be sensitive toward insecticides but its sensitivity toward heavy metals was least reported. Herein, a sensitive assay for heavy metals has been pursued using AChE in a rapid and economic manner. The AChE from a mudskipper, Periophthalmodon schlosseri has been found to be sensitive toward copper [ mercury [ chromium [ and arsenic ions at the sub parts per million levels. Field trial works showed that the assay was applicable in detecting heavy metals pollution from effluents of industrial sites at near real time and verified using ICP-OES and Flow Injection Mercury System (FIMS 400). Furthermore, hierarchical cluster analyses of inhibition profiles were performed, revealing a comparable capability of the AChE compared to the gold standard of Microtox™ method.

Toxicants removal through microorganism’s action is intensely being sought due to economic reasons. The aim of this paper is to isolate a bacterium that is able to reduce molybdenum blue and at the same time can grow on the detergent Sodium Dodecyl Sulfate (SDS). Biochemical analysis resulted in a tentative identification of the bacterium as Enterobacter sp. strain Neni-13. Growth on SDS showed a 100 % removal at 800 mg/L SDS within 12 days. The removal of SDS from media was confirmed through Methylene Blue Active Substances Assay. Molybdenum reduction using sodium molybdate as a substrate was characterized using a microplate assay. The optimum pH and temperature for molybdenum reduction was between 6.0 and 6.5, and at 37 °C, respectively. Glucose was the best electron donor for molybdate reduction. Phosphate and molybdate concentrations of between 2.5 and 5.0 mM and at 15 mM, were optimal for molybdate reduction, respectively. Molybdate reduction was inhibited by the heavy metals mercury, silver, copper and chromium at 2 ppm. The ability of this bacterium to detoxify molybdate and degrade the SDS makes this bacterium an important tool for bioremediation of toxicants in soil.

Molybdenum is toxic to ruminants and the process of spermatogenesis in catfish and mice. The bioremediation of heavy metals including molybdenum is being intensely studied. More efficient reducers are being isolated. An advantage of microbial molybdate reduction to molybdenum blue is the intense blue product absorbs wavelength strongly in the far red region whilst cells without the addition of molybdenum showed little absorption in this region. This means that no sample treatments such as centrifugation are needed and the readings can be taken straight away. In this work we developed a microplate or a microtiter plate assay for monitoring molybdenum blue production from a bacterium. The molybdenum blue produced when measured from a microplate gave about 2 times less absorbance intensity compared to measurement using a normal cuvette, but is adequate for characterization works as the absorbance obtained was 0.886 compared to 1.709 for measurement using cuvette. The development of microplate format for monitoring microbial reduction to molybdenum blue is simple to perform and would ensure works on the characterizations of novel molybdenum reducers can potentially be carried out in a few days instead of a few weeks.