Syzygium aromaticum L.(Clove)Essential Oil as a Reducing Agent for the Green Synthesis of Silver Nanoparticles

The present investigation details a green synthesis of silver nanoparticles (AgNP) using the essential oil of Syzygium aromaticum L. (clove) as reducing agent, which is a matrix with a high content of eugenol, an important compound for the reducing action of silver nitrate. The synthesis of AgNP was performed at different pH conditions (pH 7, 8, 9 and 10), and was monitored by UV-Vis Spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscopy. The synthesized nanoparticles presented characteristic Surface Plasmon Resonance bands with maximum absorbance between 405 and 460 nm. The DLS analysis revealed particle sizes from 31 to 72 nm and zeta potential between -30.1 and -50.8 mV indicating good stability against the agglomeration of the particles in solution. The micrographs obtained by TEM showed different particle shapes and a predominance of spherical-shaped nanoparticles, and average size ranging from 27 to 94 nm. The clove-based silver nanoparticles were efficient in controlling the growth of Escherichia coli and Staphylococcus aureus bacteria, and the minimum inhibitory concentration ranged from 60 to 100 μL/mL. This study highlights the feasibility of clove essential oil as an alternative for the synthesis of silver nanoparticles by a simple, inexpensive and eco-friendly method.

Morphological and molecular diversity of arbuscular mycorrhizal fungi in revegetated iron-mining site has the same magnitude of adjacent pristine ecosystems

Arbuscular mycorrhizal fungi（AMF） are important during revegetation of mining sites, but few studies compared AMF community in revegetated sites with pristine adjacent ecosystems. The aim of this study was to assess AMF species richness in a revegetated iron-mining site and adjacent ecosystems and to relate AMF occurrence to soil chemical parameters. Soil samples were collected in dry and rainy seasons in a revegetated iron-mining site（RA） and compared with pristine ecosystems of forest（FL）, canga（NG）,and Cerrado（CE）. AMF species were identified by spore morphology from field and trap cultures and by LSU r DNA sequencing using Illumina. A total of 62 AMF species were recovered, pertaining to 18 genera and nine families of Glomeromycota. The largest number of species and families were detected in RA, and Acaulospora mellea and Glomus sp1 were the most frequent species. Species belonging to Glomeraceae and Acaulosporaceae accounted for 42%–48% of total species richness. Total number of spores and mycorrhizal inoculum potential tended to be higher in the dry than in the rainy season, except in RA. Sequences of uncultured Glomerales were dominant in all sites and seasons and five species were detected exclusively by DNA-based identification. Redundancy analysis evidenced soil p H,organic matter, aluminum, and iron as main factors influencing AMF presence. In conclusion, revegetation of the iron-mining site seems to be effective in maintaining a diverse AMF community and different approaches are complementary to reveal AMF species, despite the larger number of species being identified by traditional identification of field spores.