Resistance of extremely halophilic archaea to zinc and zinc oxide nanoparticles

Bhakti B Salgaonkar,Judith Maria Bragança,Deepthi Das

doi:10.1007/s13204-015-0424-8

Bhakti B Salgaonkar, Judith Maria Bragança + Show 1 more

Open Access

https://doi.org/10.1007/s13204-015-0424-8

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Abstract

Industrialization as well as other anthropogenic activities have resulted in addition of high loads of metal and/or metal nanoparticles to the environment. In this study, the effect of one of the widely used heavy metal, zinc (Zn) and zinc oxide nanoparticles (ZnO NPs) on extremely halophilic archaea was evaluated. One representative member from four genera namely Halococcus, Haloferax, Halorubrum and Haloarcula of the family Halobacteriaceae was taken as the model organism. All the haloarchaeal genera investigated were resistant to both ZnCl2 and ZnO NPs at varying concentrations. Halococcus strain BK6 and Haloferax strain BBK2 showed the highest resistance in complex/minimal medium of up to 2.0/1.0 mM ZnCl2 and 2.0/1.0–0.5 mM ZnO NP. Accumulation of ZnCl2/ZnO NPs was seen as Haloferax strain BBK2 (287.2/549.6 mg g−1) > Halococcus strain BK6 (165.9/388.5 mg g−1) > Haloarcula strain BS2 (93.2/28.5 mg g−1) > Halorubrum strain BS17 (29.9/16.2 mg g−1). Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDX) analysis revealed that bulk ZnCl2 was sorbed at a higher concentration (21.77 %) on the cell surface of Haloferax strain BBK2 as compared to the ZnO NPs (14.89 %).

Highlights

Rapid industrialization and other anthropogenic activities have resulted in drastic environmental pollution
Accumulation of ZnCl2/zinc oxide nanoparticles (ZnO NPs) was seen as Haloferax strain BBK2 (287.2/549.6 mg g-1) [ Halococcus strain BK6 (165.9/388.5 mg g-1) [ Haloarcula strain BS2 (93.2/28.5 mg g-1) [ Halorubrum strain BS17 (29.9/16.2 mg g-1)
Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDX) analysis revealed that bulk ZnCl2 was sorbed at a higher concentration (21.77 %) on the cell surface of Haloferax strain BBK2 as compared to the ZnO NPs (14.89 %)

Summary

Introduction

Rapid industrialization and other anthropogenic activities have resulted in drastic environmental pollution. Natural processes like surface runoffs, weathering and/or erosion and anthropogenic activities like mining, industrial effluents, agricultural runoffs and sewage have led to the accumulation of toxic metals and their derivatives like nanoparticles in the environment (Paula et al 2013; Zhao et al 2012). Zinc and zinc oxide nanoparticles (ZnO NPs) are of high concern because of their increasing demand in electroplating, galvanization, cosmetics, sunscreens, paints, food industry, anticancer drugs, antimicrobials, ceramics, and semiconductors (Monteiro et al 2011; Li et al 2011). There are numerous reports on resistance and/or tolerance of metals by bacterial strains either individually or in consortium (non halophilic) (Gadd 2009). Various mechanisms of Zn resistance such as physical bioadsorption/sorption, ion exchange, bioprecipitation and intracellular accumulation in microorganisms such as bacteria (Gram-positive and Gram-negative), cyanobacteria (Microcystis aeruginosa) archaea (Halobacterium saccharovorum) and eukarya (diatoms) have been revealed (Gadd 2009; Green-Ruiz et al 2008; Zeng and Wang 2009; Guine et al 2006; Mangold et al 2013; Williams et al 2013; Gelabert et al 2006)

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