Synthesis, characterization and kinetic study of silver and gold nanoparticles produced by the archaeon Haloferax volcanii.

AIMS: To evaluate the ability of the haloarchaeon Haloferax volcanii to produce Ag and Au nanoparticles (NPs) and to characterize the obtained material in order to find relevant properties for future potential applications. METHODS AND RESULTS: Nanoparticles were produced by incubating H. volcanii cells with the corresponding metal salt. In the presence of precursor salts, cultures evidenced a colour change associated to the formation of metallic nanostructures with plasmonic bands located in the visible range of the spectrum. X-ray fluorescence analysis confirmed the presence of Ag and Au in the NPs which were spherical, with average sizes of 25 nmol l-1 (Ag) and 10 nmol l-1 (Au), as determined by electronic microscopy. Fourier transformed infrared spectroscopy indicated that both types of NPs showed a stable protein capping. Ag NPs evidenced antibacterial activity and Au NPs improved the specificity of polymerase chain reaction reactions. Au and Ag NPs were able to reduce 4-nitrophenol when incubated with NaBH4 . CONCLUSIONS: Haloferax volcanii is able to synthesize metallic NPs with interesting properties for technological applications. SIGNIFICANCE AND IMPACT OF THE STUDY: Our data demonstrate the ability of H. volcanii to synthesize metal NPs and constitutes a solid starting point to deepen the study and explore novel applications.

Bacillus subtilis as a bioindicator for estimating pentachlorophenol toxicity and concentration.

Pentachlorophenol (PCP) and its sodium salt (Na-PCP) are extremely toxic chemicals responsible for important soil and groundwater pollution, mainly caused by wastes from wood-treatment plants, because chlorinated phenols are widely used as wood preservatives. The methods most commonly used for routine analysis of pesticides such as PCP and Na-PCP are high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS). A variety of rapid biological screening tests using marine organisms, bioluminescent bacteria, and enzymes have also been reported. In this study, rapid biological screening analysis using Bacillus subtilis was developed, to assess the biodegradation of PCP and its by-products in liquid samples. An empirical model is proposed for spectrophotometric analysis of Na-PCP concentration after growth of Bacillus subtilis.