Journal Article

Ochrobactrum sp. MPV1 from a dump of roasted pyrites can be exploited as bacterial catalyst for the biogenesis of selenium and tellurium nanoparticles

Dell’Anna, Rossana, Vallini, Giovanni, Zonaro, Emanuele, Piacenza, Elena, Monti, Francesca, Lampis, Silvia, Presentato, Alessandro

2017

Overview

Background Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles—both inside and outside the cells—characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have attracted great interest due to their photoelectric and semiconducting properties. In addition, their exploitation as antimicrobial agents is currently becoming an area of intensive research in medical sciences. Results In the present study, the bacterial strain Ochrobactrum sp. MPV1, isolated from a dump of roasted arsenopyrites as residues of a formerly sulfuric acid production near Scarlino (Tuscany, Italy) was analyzed for its capability of efficaciously bioreducing the chalcogen oxyanions selenite (SeO 3 2− ) and tellurite (TeO 3 2− ) to their respective elemental forms (Se 0 and Te 0 ) in aerobic conditions, with generation of Se- and Te-nanoparticles (Se- and TeNPs). The isolate could bioconvert 2 mM SeO 3 2− and 0.5 mM TeO 3 2− to the corresponding Se 0 and Te 0 in 48 and 120 h, respectively. The intracellular accumulation of nanomaterials was demonstrated through electron microscopy. Moreover, several analyses were performed to shed light on the mechanisms involved in SeO 3 2− and TeO 3 2− bioreduction to their elemental states. Results obtained suggested that these oxyanions are bioconverted through two different mechanisms in Ochrobactrum sp. MPV1. Glutathione (GSH) seemed to play a key role in SeO 3 2− bioreduction, while TeO 3 2− bioconversion could be ascribed to the catalytic activity of intracellular NADH-dependent oxidoreductases. The organic coating surrounding biogenic Se- and TeNPs was also characterized through Fourier-transform infrared spectroscopy. This analysis revealed interesting differences among the NPs produced by Ochrobactrum sp. MPV1 and suggested a possible different role of phospholipids and proteins in both biosynthesis and stabilization of such chalcogen-NPs. Conclusions In conclusion, Ochrobactrum sp. MPV1 has demonstrated to be an ideal candidate for the bioconversion of toxic oxyanions such as selenite and tellurite to their respective elemental forms, producing intracellular Se- and TeNPs possibly exploitable in biomedical and industrial applications.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Acid production / Aerobic conditions / Aerobic selenite reduction / Aerobic tellurite reduction / Aerobiosis / Analysis / Antimicrobial agents / Applied Microbiology / Arsenic / Arsenicals - metabolism / Axenic Culture - methods / Bacteria / Bacterial-metalloid interactions / Bioavailability / Biocompatibility / Bioconversion / Biogenically synthesized nanoparticles / Biosynthesis / Biotechnology / Catalysis / Catalytic activity / Cell culture / Chalcogen metalloids / Chemistry / Chemistry and Materials Science / Dehydrogenases / E coli / Electron microscopy / Enzymology / Fourier transforms / Genetic Engineering / Glutathione / Gypsum / Hazardous substances / Industrial applications / Infrared analysis / Infrared spectroscopy / Intracellular / Iron Compounds - metabolism / Italy / Medical research / Medical science / Membrane lipids / Metal Nanoparticles - chemistry / Microbial Genetics and Genomics / Microbiology / Microscopy, Electron / Minerals - metabolism / NADH / Nanomaterials / Nanoparticles / Nanotechnology / Nicotinamide adenine dinucleotide / Ochrobactrum / Ochrobactrum - chemistry / Ochrobactrum - isolation & purification / Ochrobactrum - metabolism / Ochrobactrum - ultrastructure / Ochrobactrum sp. MPV1 / Organic coatings / Oxidases / Phospholipids / Photoelectricity / Physiological aspects / Pure culture / Pyrite / Selenious Acid - metabolism / Selenite / Selenites / Selenium / Selenium - chemistry / Selenium - metabolism / Sulfides - metabolism / Sulfuric acid / Tellurite / Tellurium / Tellurium - chemistry / Tellurium - metabolism / Tellurium dioxide