Microbial Reduction and Precipitation of Vanadium by Shewanella oneidensis

Abstract

Shewanella oneidensis couples anaerobic oxidation of lactate, formate, and pyruvate to the reduction of vanadium pentoxide (V V ). The bacterium reduces V V (vanadate ion) to V IV (vanadyl ion) in an anaerobic atmosphere. The resulting vanadyl ion precipitates as a V IV -containing solid.Vanadium is a transition metal which, at neutral pH, can exist in two oxidation states, V IV (vanadyl ion, cationic species VO 2ϩ ), and V V (vanadate ion, anionic species, H 2 VO 4 Ϫ ) (10, 11).The environmental chemistry of vanadium is complex. Vanadium is an abundant element that has proven to be a valuable resource for different industrial applications such as vanadium alloys, oxidation catalysis in sulfuric acid manufacturing and automobile catalytic converters, photographic development, textile dyeing, and ceramic coloring. A number of bacteria are able to reduce metal compounds, most commonly iron and manganese, through anaerobic reduction. Some organisms are known to be able to reduce other metals such as arsenic, mercury, selenium, uranium, technetium, chromium, molybdenum, gold, silver, and copper (4,8,13). The microbial reduction of vanadate has also been reported (1,14). To date, two Pseudomonas strains have been described to be capable of reducing vanadium (5,15). In this study we demonstrate that the gram-negative facultative anaerobic nonfermenting bacterium Shewanella oneidensis (6) can also reduce vanadium V V . Vanadium uptake on solid media. Colonies of S. oneidensis were grown on Luria-Bertani 1% agar plates containing 5 mM vanadate at 28°C for 48 h. Plates were then exposed to hydrogen sulfide in a sealed container. Upon formation of metal sulfide, plates were examined for changes in the regions surrounding or inside bacterial colonies. A halo could be seen indicating possible sequestration of the metal. Darkening of the cells indicated accumulation or possible reduction of the metal (data not shown).Vanadate detection. To facilitate the detection and quantification of the reduction of vanadate to V IV , a vanadate detection assay was designed, based on a detection assay for chromium described by Sandel (12). Vanadate was thereby detected on the basis of its reaction with diphenylcarbazide (DPC) in acid. The assay solution was made by addition of 1% (wt/vol) DPC in acetone to an equal volume of 2 M H 2 SO 4 . A volume of 500 l of diluted sample was added to the same volume of assay solution. Absorbance was measured at 320 nm after 15 min. A standard curve was made with vanadium pentoxide dilutions. Vanadyl ions do not react in this assay.Anaerobic vanadium reduction. S. oneidensis was grown aerobically on a rotary shaker (150 rpm) at 28°C in LB medium containing 2 or 10 mM V 2 O 5 and anaerobically with a Coy anaerobic chamber (Coy Laboratories, Grass Lake, Mich.) in phosphate-buffered defined medium (7) containing 10 mM lactate as the electron donor and 2 or 10 mM V 2 O 5 as the electron acceptor. An increase in lag phase could be detected in cultures grown with 10 mM but not with 2 mM V 2 O 5 compared to c...

The periplasmic nitrate reductase in Shewanella: the resolution, distribution and functional implications of two NAP isoforms, NapEDABC and NapDAGHB

“…In addition to the catalytic NrfA subunit, NRF consists of a pentahaem cytochrome c (NrfB), an ironsulfur cluster protein on the periplasmic face of the membrane (NrfC) and a transmembrane domain (NrfD), which as the NrfABCD cluster is commonly found in cproteobacteria Hussain et al, 1994;Simon et al, 2000). The NapC homologue, CymA, has been found to be essential in S. oneidensis MR-1 for the anaerobic reduction of nitrate, nitrite, Fe(III), Mn(IV), DMSO or V(V) (Carpentier et al, 2005;Gao et al, 2009;Myers & Myers, 1997, 2000Schwalb et al, 2003). Putative CymA proteins with 68.1 % identity are encoded in the genomes of all Shewanella species that encode NAP-b.…”

“…nov. have been characterized from marine environments (Bozal et al, 2009;Park et al, 2009) and contribute to the 51 species of Shewanella identified at the time of writing (http://www.bacterio.cict.fr/). Some Shewanella species, most notably Shewanella oneidensis MR-1, can grow via the reduction of metal oxides -including Fe(III), Mn(IV), Cr(VI), U(VI), Tc(VI), V(V) -thiosulfate, elemental sulfur and arsenate (Burns & DiChristina, 2009;Carpentier et al, 2005;Konstantinidis et al, 2009;Malasarn et al, 2008;Murphy & Saltikov, 2007;Nealson & Saffarini, 1994;Nealson & Little, 1997). The respiratory versatility of Shewanella species has significant implications in bioremediation and in the assembly of microbial fuel cells (Fredrickson et al, 2008;Hou et al, 2009;Kim et al, 2002;Tiedje, 2002).…”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides – 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing Metal Toxicity and Transport

“…Anaerobic microorganisms enzymatically reduce contaminant metals such as uranium, chromium, technetium, vanadium and metalloids such as selenium thereby converting these metals to less soluble forms Lovley & Coates 2000;Carpentier et al 2003;Ortiz-Bernard et al 2004). Stimulation of metal reduction within the subsurface offers a relatively simple method to remove metal contaminants from groundwater, thereby limiting or greatly reducing further transport of contaminants downgradient (Lovley et al 1991;Lovley 1993;.…”

Caloramator mitchellensis sp. nov., a thermoanaerobe isolated from the geothermal waters of the Great Artesian Basin of Australia, and emended description of the genus Caloramator

“…Vanadium can exist in oxidation states ranging from 22 to +5, though at neutral pH vanadium commonly exists as V(V) (vanadate) and V(IV) (vanadyl), of which the former is the most toxic and mobile form (Ortiz-Bernad et al, 2004). Vanadium(V)-reducing microbes that have been reported to date include species of the genus Pseudomonas (Lyalkova & Yurkova, 1992) and the metal-reducing organisms Shewanella oneidensis (Carpentier et al, 2003) and Geobacter metallireducens (Ortiz-Bernad et al, 2004). In this paper, we describe a strictly anaerobic, thermophilic bacterium designated strain VF08 T , which reduces vanadium(V) and represents a novel species of the genus Caloramator.…”

“…Vanadium(V)-reduction was inferred when the colourless medium changed to green and/or a green precipitate was formed. Vanadium(V)-reduction was confirmed using the vanadate assay as described by Carpentier et al (2003). For this, 250 ml 1 % (w/v) diphenylcarbazide in acetone was added to 250 ml 2 M H 2 SO 4 and 500 ml diluted sample was added.…”