Aerobic bioreduction of nickel(II) to elemental nickel with concomitant biomineralization

Abstract

Although microorganisms have the potential to reduce metals, products with elementary forms are unusual. In the present study, a strain of Pseudomonas sp. MBR was tested for its ability to reduce metal ions to their elementary forms coupled to biomineralization under aerobic conditions. The Pseudomonas sp. MBR strain was able to reduce metals such as Fe(III), Mn(II), Cu(II), Ni(II), Cd(II), Co(II), Al(III), Se(IV), and Te(IV) as electron acceptors to elementary forms using citrate, lactate, pyruvate, succinate, malate, glucose, or ethanol as electron donors. Growth and reduction during biomineralization occurred within the pH range of 6.0 to 11.0 and temperature range of 4 to 40°C, with an optimum growth temperature of 28°C. The resistance of Ni (II) varied from 0.5 to 5 mM. Ni(II) reduction was still observed when nitrate was present in addition to oxygen as a potential electron acceptor. The Ni(II) reduction efficiency was related with the molar ratio of the electron donor to Ni(II). Unlike other dissimilatory metal-reducing bacteria, which oxidizes organic matter with Fe(III) or Mn (IV) as the sole electron acceptor coupled to energy production under facultative anaerobic conditions, this strain used oxygen as an electron acceptor combined with metal reduction. The aerobic metal reduction may relate to a co-metabolic reduction. Transmission electron microscopy images demonstrated that the cells had the ability to accumulate heavy metals, and that the detoxicity mechanism was intracellular metal reduction. These results suggested that the use of Pseudomonas sp. MBR could be promising for toxic heavy metal bioremediation and biological metallurgy.

Nanomicrobiology

“…and Saccharomyces cerevisiae Jha et al 2010 ZrO 2 A spherical particle of 3-11 nm produced extracellularly by Fusarium oxysporium Bansal et al 2004 CdSe A spherical particle of 9-15 nm diameter produced extracellularly by Fusarium oxysporum Kumar et al 2007 Te 0 Bacillus beveridgei produces nanocrystals of 10 x 200 (rods) when tellurite or tellurate is the final electron acceptor Baesman et al 2007 Ni 0 Pseudomonas sp. MBR is reported to reduce Ni(II) to elemental Ni by co-metabolism Zhan et al 2012 Hg 0 A strain of Enterobacter produces elemental mercury as 2-5 nm spheres inside the cells Sinha and Khare 2011…”

The magnetosome model: insights into the mechanisms of bacterial biomineralization

“…For many bacteria, biomineralization is a way to cope with an environmental toxin or a waste product, so the main elements that form the final mineral do not need to be sourced. For example, Pseudomonas alcaliphila has been shown to mineralize toxic Ni(II) to Ni(0) (Zhan et al, 2012), and Thauera selenatis manages selenite, a waste product of its respiration on selenate, by mineralizing Se(0) nanospheres (Debieux et al, 2011). In both of these cases, the resultant mineral is elemental nickel or selenium, so no further material is needed.…”

“…For example, Escherichia coli and Rhodopseudomonas palustris have both been shown to biomineralize cadmium when it is provided to them under experimental conditions (Sweeney et al, 2004; Bai et al, 2009), and AMB-1 can mineralize tellurium nanorods separately from its magnetite crystals, creating a biomagnetic method of recovering this rare element from the environment (Tanaka et al, 2010). Other organisms are able to use biomineralization to detoxify pollutants such as nickel, uranium, or silver encountered in the environment by transforming them into less bio-accessible states (Klaus et al, 1999; Zhan et al, 2012; Sousa et al, 2013). Still others manage their own waste products with biomineralization, including photosynthesizing cyanobacteria (Couradeau et al, 2012), and selenite-respiring bacteria (Debieux et al, 2011).…”

CHROTRAN 1.0: A mathematical and computational model for in situ heavy metal remediation in heterogeneous aquifers

“…This has inspired efforts to manipulate in situ conditions to stimulate microbial growth and achieve biologically mediated metals reduction. This technique has been demonstrated, at least in some settings, for chromium, uranium and selenium (Lovley, 1993(Lovley, , 1995, nickel (Zhan et al, 2012), technetium (Istok et al, 2004), and copper (Andreazza et al, 2010), and has been noted as a viable bioremediation technique by recent critical reviews (Hashim et al, 2011;Wu et al, 2010). Bioprecipitation, a process by which microbiological exudates react with metals to produce an insoluble compound, has been widely observed (Malik, 2004;Van Roy et al, 2006;Radhika et al, 2006) and has been noted by Wu et al (2010) as a remediation method.…”