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Gnanasekaran, C., Govindan, R., Chelliah, C. K., Govindan, R., Ranganathan, P., Muthuchamy, M., et al. (2023). Isolation and molecular detection of endophytic actinomycetes Nocardiopsis dassonvillei DMS 1 (MH900216) from marine sea grasses with bacterial inactivation. Biocatal. Agric. Biotechnol., 54, 102938.
Abstract: In recent years, new antibiotics have been discovered around the world in order to inhibit multi drug resistant (MDR) pathogens. To overcome this problem, marine actinomycetes are an alternative choice for producing new bioactive compounds that inhibit MDR bacteria. The typical endophytic actinomycete (EA) Nocardiopsis dassonvillei (N. dassonvillei) DMS 1 (MH900216) was isolated from marine Sea grasses by surface sterilization method. After surface sterilization, it was confirmed that the pure, dry, white-colored spore producing colonies emerged from the internal tissue of the Sea grasses. The crude extract of N. dassonvillei DMS 1 (MH900216) demonstrated 8 and 10-mm zones of inhibition against A. baumannii and K. pneumoniae, respectively. The composition of N. dassonvillei DMS 1 (MH900216) with potential anti-bacterial properties was studied by GC-MS analysis and exhibited 22 chemical compounds. Subsequently, the molecular identification and phylogenetic construction of the isolated EA strain was confirmed as N. dassonvillei DMS 1 (MH900216). The liquid-liquid extraction of the compound demonstrated 24-and 26-mm zones of inhibition against A. baumannii and K. pneumoniae, respectively. Furthermore, the purified crude compound demonstrated 92% and 94% cell death against A. baumannii and K. pneumoniae, respectively, at a minimum inhibitory concentration of 500 mu g/mL. Overall, the present study demonstrated the antibacterial properties of the EA N. dassonvillei DMS 1 (MH900216) isolated from Sea grasses and their importance as alternative sources for discovering new antibiotics to inhibit MDR bacteria.
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Vera, R., Valverde, B., Olave, E., Diaz-Gomez, A., Sanchez-Gonzalez, R., Munoz, L., et al. (2022). Corrosion Behavior of Copper Exposed in Marine Tropical Atmosphere in Rapa Nui (Easter Island) Chile 20 Years after MICAT. Metals, 12(12), 2082.
Abstract: Atmospheric corrosion of copper, exposed on a tropical island in the South-Central Pacific Ocean, was reported and compared with those of a very similar study at the same site conducted 20 years earlier. The new measurements-taken over three years of exposure, from 2010 to 2013-quantified corrosion by mass loss, characterized corrosion products by X-ray diffraction (DRX) and Raman techniques, observed the attack morphology by Scanning Electron Microscope (SEM), and evaluated the patina resistance using electrochemical techniques. The results showed a copper corrosivity category of C4, and the main copper patina compound, cuprite, was porous, nonhomogeneous, and thin. Electrochemical measurements showed cuprite layer growth as a function of the exposure time, and the morphology did not favor corrosion protection. Finally, when comparing the results to those of a study 22 years previous, the copper corrosion rates increased only slightly, even with increased contaminants associated with growing local populations and continuous tourism on the island.
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Vera, R., Valverde, B., Olave, E., Sanchez, R., Diaz-Gomez, A., Munoz, L., et al. (2023). Atmospheric corrosion and impact toughness of steels: Case study in steels with and without galvanizing, exposed for 3 years in Rapa Nui Island. Heliyon, 9(7), e17811.
Abstract: We studied atmospheric corrosion on Rapa Nui Island, using galvanized and non-galvanized SAE 1020 steel samples exposed on racks. We also added Charpy samples of both materials to directly determine the effect of corrosion rate on these materials' impact toughness. The results indicated a correlation between corrosion rate and toughness loss in the studied materials. In the corrosion study, we could also demonstrate the effect from increased insular population growth on con-taminants which aid atmospheric corrosivity. Results showed that atmospheric SO2 has tripled compared with similar corrosion studies done 20 years ago (Mapa Iberoamericano de Corrosi & PRIME;on, MICAT), increasing corrosion rates. Our results show how human factors can influence changes in environmental variables that strengthen corrosion.
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