Antibacterial Mechanisms of Reduced Iron-Containing Smectite-Illite Clay Minerals.

Reduced nontronite has been demonstrated to be antibacterial through the production of hydroxyl radical (•OH) from the oxidation of structural Fe(II). Herein, we investigated the antibacterial activity of more common smectite-illite (S-I) clays toward Escherichia coli cells, including montmorillonite SWy-3, illite IMt-2, 50-50 S-I rectorite RAr-1, 30-70 S-I ISCz-1, and nontronite NAu-2. Under an oxic condition, reduced clays (with a prefix r before mineral names) produced reactive oxygen species (ROS), and the antibacterial activity followed the order of rRAr-1 > rSWy-3 ≥ rNAu-2 ≫ rIMt-2 ≥ rISCz-1. The strongest antibacterial activity of rRAr-1 was contributed by a combination of •OH and Fe(IV) generated from structural Fe(II)/adsorbed Fe2+ and soluble Fe2+, respectively. Higher levels of lipid and protein oxidation, intracellular ROS accumulation, and membrane disruption were consistent with this antibacterial mechanism of rRAr-1. The antibacterial activity of other S-I clays depended on layer expandability, which determined the reactivity of structural Fe(II) and the production of •OH, with the expandable smectite being the most antibacterial and nonexpandable illite the least. Our results provide new insights into the antibacterial mechanisms of clay minerals.

Biochemical and teratogenic effects of a mixture of pyriproxyfen and glyphosate.

The mixture of agrochemicals can be made to improve pest control or accidentally. In this way, the effects on non-target organisms are a critical aspect of the environment and heath. Thus, this work aimed to show how a mixture of pyriproxyfen, and glyphosate can impair biochemical routes and embryonic development. Zebrafish embryos 0-72 hpf were exposed to 0.001-1 µg/mL of pyriproxyfen, glyphosate, and a mixture of both pesticides. The ADMETox was evaluated in silico. The FET-test was used to estimate teratogenic effects. The biochemical effects were estimated using AChE, SOD, and CAT as parameters. ROS generation was estimated using 30 µM H2DCF-DA and 5 µM DHE. The ADMETox reveals that intestinal absorption and P-glycoprotein are the main sites for PPx and Gly adsorption. The distribution parameters were diverse. PPx + Gly at 0.1 µg/mL leads to 50 % of lethality and at 1 µg/mL 100 % of lethality. PPx + Gly leads to a 22 % of lack of somite formation at 1 µg/mL. The heart rate was reduced by >10 % in all concentrations tested. The AChE has a decrease with IC20 19.6 µM and IC50 261.5 µM. SOD showed a reduction of 28 % to PPx and CAT was reduced by 58 % to PPx + Gly and Gly at 1 µg/mL. Glyphosate does not increase unspecific ROS generation. The superoxide generation was 2× higher in the PPx + Gly at 1 µg/mL. Summarily, was observed that the mixture of PPx + Gly potentiated the toxic effects. This finding suggests a possible synergism between the PPx and Gly even at lower concentrations.