Biological Synthesis of Metallic and Metal Sulfide Nanoparticles using Halophilic Archaea and Bacteria

Abstract

Microbial synthesis of nanoparticles presents an eco-friendly approach for nano-abrication. newlineNumerous bacteria, fungi, yeasts, and viruses have been used for biosynthesis of newlinenanomaterials. Haloarchaea, however have not yet been exploited for the same, whilst very newlinefew halophilic bacteria have been shown to synthesise nanoparticles. In the present work, we demonstrate the synthesis of various metallic and metal sulphide nanoparticles by haloarchaea and halophilic bacteria. The haloarchaea, Halococcus salifodinae BK3, H. salifodinae BK6, H. salifodinae BK7, H. salifodinae BK11 and H. salifodinae BK18 were screened for their ability to synthesise nanoparticles. The halophilic bacteria screened for nanoparticles synthesis newlineinclude Halomonas aquamarina MTCC 4661, Halobacillus sp. MTCC 6516, and Idiomarina newlinesp. PR58-8. The haloarchaea exhibited optimum growth in NTYE, while the medium supporting optimum growth for Idiomarina sp. PR58-8, Halobacillus sp. MTCC 6516 and H. newlineaquamarina MTCC 4661 was ZMB, 3.5% NTYE, and NB with 2% NaCl, respectively. Amongst the halophilic archaea screened, H. salifodinae BK3 and H. salifodinae BK6 exhibited the ability to synthesise silver nanoparticles (SNPs); H. salifodinae BK18 could synthesise selenium nanoparticles (SeNPs); and H. salifodinae BK3 could synthesise tellurium newlinenanoparticles (TeNPs). Similarly, amongst the halophilic bacteria screened, only Idiomarina newlinesp. PR58-8 could successfully synthesise SeNPs and lead (IV) sulphide nanoparticles newline(PbS2NPs). Halococcus salifodinae BK3 and H. salifodinae BK6 were found to be tolerant to silver nitrate and grew well up to a concentration of 0.5 mM AgNO3. Upon adaptation to silver nitrate these isolates exhibited growth kinetics similar to that of the control. NADH dependent nitrate reductase was involved in silver tolerance, reduction, synthesis of SNPs, as evident from a metal dependent increase in enzyme activity. Silver nanoparticles synthesised by H.salifodinae BK3 (SNPs-BK3) exhibited face centred cubic structure with crystallite domain