Formation of Se (0) Nanoparticles by Duganella sp. and Agrobacterium sp. isolated from Se-laden soil of North-East Punjab, India

Abstract

BackgroundSelenium (Se) is an essential trace element, but is toxic at high concentrations. Depending upon the geological background, the land use or on anthropogenic pollution, different amounts of Se may be present in soil. Its toxicity is related to the oxyanions selenate and selenite as they are water soluble and bioavailable. Microorganisms play an important role in Se transformations in soil and its cycling in the environment by transforming water-soluble oxyanions into water insoluble, non-toxic elemental Se (0). For this study, soil samples were collected from selenium-contaminated agricultural soils of Punjab/India to enrich and isolate microbes that interacted with the Se cycle.ResultsA mixed microbial culture enriched from the arable soil of Punjab could reduce 230 mg/l of water soluble selenite to spherical Se (0) nanoparticles during aerobic growth as confirmed by SEM-EDX. Four pure cultures (C 1, C 4, C 6, C 7) of Gram negative, oxidase and catalase positive, aerobic bacteria were isolated from this mixed microbial consortium and identified by 16 S rDNA gene sequence alignment as two strains of Duganella sp. (C 1, C 4) and two strains of Agrobacterium sp.(C 6, C 7). SEM/TEM-EDX analyses of the culture broth of the four strains revealed excretion of uniformly round sharply contoured Se (0) nanoparticles by all cultures. Their size ranged from 140–200 nm in cultures of strains C 1 and C 4, and from 185–190 nm in cultures of strains C 6 and C 7. Both Duganella sp. revealed better selenite reduction efficiencies than the two Agrobacterium sp.ConclusionsThis is the first study reporting the capability of newly isolated, aerobically growing Duganella sp. and Agrobacterium sp. from soils of Punjab/India to form spherical, regularly formed Se (0) nanoparticles from water soluble selenite. Among others, the four strains may significantly contribute to the biogeochemical cycling of Se in soil. Bioconversion of toxic selenite to non-toxic Se (0) nanoparticles under aerobic conditions in general may be useful for detoxification of agricultural soil, since elemental Se may not be taken up by the roots of plants and thus allow non-dangerous fodder and food production on Se-containing soil.

Bacillus cereus, selenite-reducing bacterium from contaminated lake of an industrial area: a renewable nanofactory for the synthesis of selenium nanoparticles

“…Other reported aerobic strains are Pseudomonas agglomerans, (Torres et al 2012), P. aeruginosa JS-11 (Dwivedi et al 2013), P. stutzeri (Lortie et al 1992), P. alcaliphila (Zhang et al 2011), Duganella sp., Agrobacterium sp. (Bajaj et al 2012), Zooglea ramigera (Srivastava and Mukhopadhyay 2013), Streptomyces minutiscleroticus M10A62 (Ramya et al 2015), Acinetobacter sp. E6.2 (Durán et al 2015), Comamonas testosteroni S44 (Zheng et al 2014), Klebsiella pneumonia (Fesharaki et al 2010), Lactobacillus sp, Bifidobacter sp., and Streptococcus thermophilus (Eszenyi et al 2011).…”

“…The bacterial reduction of selenium oxyanions such as selenite to elemental selenium is one of the major biogeochemical processes involved in selenium removal from the agricultural drainage water and sediments. Thus, the bacteria play a key role in the biogeochemical cycling of selenium (Bajaj et al 2012).…”

“…In addition, from the soil of a antimony mine from Lengshuijiang, southern China (Zheng et al 2014), soil of a magnesite mine from Salem, India (Ramya et al 2015), soil of a coal mine from West Bengal, India (Dhanjal and Cameotra 2010), selenium laden agricultural soil of North-East Punjab, India (Bajaj et al 2012), soil of mangrove forest from Bhitarkanika, Orissa, India (Mishra et al 2011), rhizosphere soil of a selenium hyperaccumulator legume grown in seleniferous mine from Sardina, Italy (Lampis et al 2014), rhizosphere of wheat grown in herbicide contaminated soil (Dwivedi et al 2013), and rhizosphere of cereal plants grown in ash-derived volcanic soil of southern Chile (Durán et al 2015). Others include rock fragments of black oil shale from Haenam, Korea (Tam et al 2010), food wastes collected from local market of Giza, Egypt (Khiralla and El-Deeb 2015), sub gingival dental plaque (Pearce et al 2008) etc.…”

Biochemical Changes in Nostoc linckia Associated with Selenium Nanoparticles Biosynthesis

“…The research in the field of nanotechnology has been stimulated by large technological and medical applications of nanoparticles [1]. Selenium possesses excellent photoelectrical and semiconductor properties, which make it extensively used in the production of photovoltaic cells, photographic exposure meters, xerography, and the glass industry [2][3][4][5][6].…”

Microbial Transformations of Selenium Species of Relevance to Bioremediation

“…Microbial reduction occurs either in the periplasmic space (intracellularly) (23)(24)(25) or extracellularly (26)(27)(28). The reduction of Se oxyanions to Se 0 nanoparticles can also be mediated aerobically by diverse species of bacteria, namely, selenium-resistant bacteria (29)(30)(31)(32). Several investigations have dealt with the mechanisms of microbial formation of Se nanoparticles (33)(34)(35).…”