Synthesis of silver nanoparticles using haloarchaeal isolate Halococcus salifodinae BK3.

Numerous bacteria, fungi, yeasts and viruses have been exploited for biosynthesis of highly structured metal sulfide and metallic nanoparticles. Haloarchaea (salt-loving archaea) of the third domain of life Archaea, on the other hand have not yet been explored for nanoparticle synthesis. In this study, we report the intracellular synthesis of stable, mostly spherical silver nanoparticles (AgNPs) by the haloarchaeal isolate Halococcus salifodinae BK3. The culture on adaptation to silver nitrate exhibited growth kinetics similar to that of the control. NADH-dependent nitrate reductase was involved in silver tolerance, reduction, synthesis of AgNPs, and exhibited metal-dependent increase in enzyme activity. The AgNPs preparation was characterized using UV-visible spectroscopy, XRD, TEM and EDAX. The XRD analysis of the nanoparticles showed the characteristic Bragg peaks of face-centered cubic silver with crystallite domain size of 22 and 12 nm for AgNPs synthesized in NTYE and halophilic nitrate broth (HNB), respectively. The average particle size obtained from TEM analysis was 50.3 and 12 nm for AgNPs synthesized in NTYE and HNB, respectively. This is the first report on the synthesis of silver nanoparticles by haloarchaea.

Halogenated metabolites from the new Okinawan red alga Laurencia yonaguniensis.

A novel brominated diterpene based on the rare neoirieane skeleton, named neoirietetraol (1), has been isolated along with a halogenated C15 acetogenin, (3Z)-laurenyne (2), from a new Laurencia species, L.yonaguniensis Masuda et Abe, species inedita, collected at Yonaguni Island, Okinawa Prefecture, Japan. The structures of these metabolites were elucidated by spectroscopic data (IR, 1H NMR, 13C NMR, 2D NMR, and MS). Neoirietetraol (1) was toxic to the brine shrimp (Altemia salina; LC50, 40.1 microM) and also showed weak antibacterial activities against two marine bacteria, Alcaligenes aquamarinus and Escherichia coli.