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Nanoparticle (NP) synthesis using biological resources as reducing agents is an eco-friendly and simple strategy compared to the traditional physical/chemical methods. The ability of microorganisms of the Archaea domain to synthesize metal NPs has been explored to a limited extent. Metal NPs have been applied in several fields including catalysis, agriculture, biomedicine, electronics, and optics. Recently we reported that the halophilic archaeon Haloferax volcanii is capable of synthesizing silver and gold NPs. In this work, we present a simple protocol for the obtention of metal NPs using this microorganism which may be also used as a starting point for assaying NP biosynthesis in other haloarchaea.

Rhomboids are conserved intramembrane serine proteases involved in cell signaling processes. Their role in prokaryotes is scarcely known and remains to be investigated in Archaea. We previously constructed a rhomboid homologue deletion mutant (ΔrhoII) in Haloferax volcanii, which showed reduced motility, increased novobiocin sensitivity, and an N- glycosylation defect. To address the impact of rhoII deletion on H. volcanii physiology, the proteomes of mutant and parental strains were compared by shotgun proteomics. A total of 1847 proteins were identified (45.8% of H. volcanii predicted proteome), from which 103 differed in amount. Additionally, the mutant strain evidenced 99 proteins with altered electrophoretic migration, which suggested differential post-translational processing/modification. Integral membrane proteins that evidenced variations in concentration, electrophoretic migration, or semitryptic cleavage in the mutant were considered as potential RhoII targets. These included a PrsW protease homologue (which was less stable in the mutant strain), a predicted halocyanin, and six integral membrane proteins potentially related to the mutant glycosylation (S-layer glycoprotein, Agl15) and cell adhesion/motility (flagellin1, HVO-1153, PilA1, and PibD) defects. This study investigated for the first time the impact of a rhomboid protease on the whole proteome of an organism. Fil: Costa, Mariana Inés. Universidad Nacional de Mar del Plata; Argentina Fil: Cerletti, Micaela. Universidad Nacional de Mar del Plata; Argentina Fil: Paggi, Roberto Alejandro. Universidad Nacional de Mar del Plata; Argentina Fil: Trötschel, Christian. Ruhr Universität Bochum; Alemania Fil: de Castro, Rosana Esther. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; Argentina Fil: Poetsch, Ansgar. Ruhr Universität Bochum; Alemania Fil: Gimenez, Maria Ines. Universidad Nacional de Mar del Plata; Argentina