Biomagnetic Recovery and Bioaccumulation of Selenium Granules in Magnetotactic Bacteria

Abstract

Using microorganisms to remove waste and/or neutralize pollutants from contaminated water is attracting much attention due to the environmentally friendly nature of this methodology. However, cell recovery remains a bottleneck and a considerable challenge for the development of this process. Magnetotactic bacteria are a unique group of organisms that can be manipulated by an external magnetic field due to the presence of biogenic magnetite crystals formed within their cells. In this study, we demonstrated an account of accumulation and precipitation of amorphous elemental selenium nanoparticles within magnetotactic bacteria alongside and independent of magnetite crystal biomineralization when grown in a medium containing selenium oxyanion (SeO 3 2؊ ). Quantitative analysis shows that magnetotactic bacteria accumulate the largest amount of target molecules (Se) per cell compared with any other previously reported nonferrous metal/metalloid. For example, 2.4 and 174 times more Se is accumulated than Te taken up into cells and Cd 2؉ adsorbed onto the cell surface, respectively. Crucially, the bacteria with high levels of Se accumulation were successfully recovered with an external magnetic field. The biomagnetic recovery and the effective accumulation of target elements demonstrate the potential for application in bioremediation of polluted water. IMPORTANCEThe development of a technique for effective environmental water remediation is urgently required across the globe. A biological remediation process of waste removal and/or neutralization of pollutant from contaminated water using microorganisms has great potential, but cell recovery remains a bottleneck. Magnetotactic bacteria synthesize magnetic particles within their cells, which can be recovered by a magnetic field. Herein, we report an example of accumulation and precipitation of amorphous elemental selenium nanoparticles within magnetotactic bacteria independent of magnetic particle synthesis. The cells were able to accumulate the largest amount of Se compared to other foreign elements. More importantly, the Se-accumulating bacteria were successfully recovered with an external magnetic field. We believe magnetotactic bacteria confer unique advantages of biomagnetic cell recovery and of Se accumulation, providing a new and effective methodology for bioremediation of polluted water.

Influence of Temperature on the Bacterial Community in Substrate and Extracellular Enzyme Activity ofAuricularia cornea

“…Since the early 1980s, A. cornea has been artificially cultivated in China, and its social demands have recently increased greatly owing to its obvious advantages. Like other edible mushrooms, temperature, enzyme and microbiota greatly influence A. cornea during growth, which could lead to changes in polysaccharide and microelements in the sporocarp [ 10 , 11 ]. Among all factors that influence the growth of A. cornea , temperature has the greatest effect and can determine the output and quality of A. cornea .…”

Applications of Magnetotactic Bacteria, Magnetosomes and Magnetosome Crystals in Biotechnology and Nanotechnology: Mini-Review

“…The incorporation of another transition metal in magnetosome magnetite modified the magnetic properties of the crystals and could therefore lead to the design of new biomaterials with specific, possibly tailor-made magnetic properties. Based on the absorption and immobilization of metals from culture medium and the fact that MTB can be magnetically removed from sediment and water, the use of these microorganisms in bioremediation has been proposed by several investigators [ 84 , 85 , 86 , 87 ]. Tanaka and colleagues [ 84 ] showed that cells of Ms. magneticum AMB-1 are relatively resistant to tellurium and able to concentrate and crystallize this element in structures different from magnetosomes within the cell.…”

“…The magnetic concentration and recovery of cells of Ms. magneticum strain AMB-1 exposed to Cd resulted in significant removal of Cd from the growth medium when tested in vitro using a genetically modified strain of the organism that had several hexahistidine residues exposed on the cell surface [ 109 ]. In the in vitro evaluation of magnetic recovery of Se using cells of Ms. magneticum strain AMB-1 grown in culture medium containing SeO 3 2− , cells were able to reduce SeO 3 2− to Se, accumulating the element in intracytoplasmic granules not associated with magnetosome synthesis ( Figure 6 ) [ 85 ]. After the magnetic recovery of cells, 68.1% of the Se was removed from the medium ( Figure 6 ) [ 85 ].…”

Nano and Microtechnologies for the Study of Magnetotactic Bacteria

“…As MTB are able to store iron, a coculture of MTB may reveal their ecological dynamics with other micro-organisms, especially in iron cycling. Additionally, the ability of MTB to take up toxic, heavy metals such as cobalt and manganese from their natural habitats [61] has intriguing future implications for using MTB as tools for ecological waste water treatment or heavy metal removal.…”