• Journal of Microbiology and Biotechnology
• /
• v.28 no.7
• /
• pp.1209-1216
• /
• 2018

This study aimed to evaluate the antimicrobial activity of 2-phenylethynyl-butyltellurium (PEBT) in Escherichia coli and the relation to its pro-oxidant effect. For this, we carried out the disk diffusion test, minimum inhibitory concentration (MIC) assay, and survival curve analysis. We also measured the level of extracellular reactive oxygen species (ROS), activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), and level of non-protein thiols (NPSH). PEBT at 1.28 and 0.128 mg/disk exhibited antimicrobial capability in the disk diffusion test, with an MIC value of 1.92 mg/ml, whereas PEBT at 0.96, 1.92, and 3.84 mg/ml inhibited bacterial growth after a 9-h exposure. PEBT at 3.84, 1.92, and 0.96 mg/ml increased extracellular ROS production, decreased the intracellular NPSH level, and reduced the SOD and CAT activities. Glutathione or ascorbic acid in the medium protected the bacterial cells from the antimicrobial effect of PEBT. In conclusion, PEBT exhibited antimicrobial activity against E. coli, involving the generation of ROS, oxidation of NPSH, and reduction of the antioxidant defenses in the bacterial cells.

• Proceedings of the Korea Society of Environmental Toocicology Conference
• /
• 2003.10a
• /
• pp.13-13
• /
• 2003

Methylmercury (MeHg) is a ubiquitous environmental toxicant that can be exposed to humans by ingestion of contaminated food including fish and bread. MeHg has been suggested to exert its toxicity through its high reactivity to thiols, generation of arachidonic acid and reactive oxygen species (ROS), and elevation of intracellular $Ca^{2+}$ levels (［$Ca^{2+}$］$_{i}$). However, the precise mechanism has not been fully defined. Here we show that phosphatidylcholine-specific phospholipase C (PC-PLC) is a critical pathway for MeHg-induced toxicity. MeHg activated the acidic form of sphingomyelinase (A-SMase) and group IV cytosolic phospholipase $A_2$ ($cPLA_2$) downstream of PC-PLC, but these enzymes as well as protein kinase C were not linked to MeHg's toxicity. Furthermore, MeHg produced ROS, which did not cause the toxicity. However, D6O9, an inhibitor of PC-PLC, significantly reversed the toxicity in a time- and dose-dependent manner in MDCK and SH-5YSY cells. Addition of EGTA to culture media resulted in partial decrease of [$Ca^{2+}$］$_{i}$ and partially blocked cell death. In contrast, D609 completely prevented cell death with parallel decreases in diacylglycerol and ［$Ca^{2+}$］$_{i}$. Together, our findings indicated that MeHg-induced toxicity was caused by elevation of ［$Ca^{2+}$]$_{i}$ through activation of PC-PLC. The toxicity was not attributable to the signaling pathways such as $cPLA_2$, A-SMase, and PKC, or to the generation of ROS.

• Korean Journal of Weed Science
• /
• v.15 no.4
• /
• pp.247-253
• /
• 1995

The herbicide butachlor [N-(butoxymethyl)-2-chloro-N-(2,6-di-methylphenyl) acetamide] is widely used by farmers as a tool for weed management of transplanted rice(Oryza sativa L.) in Taiwan. The herbicide did not stop germination of rice and weed seeds, but strongly inhibited the subsequent growth of young shoots and roots. The inhibition was also strong on established seedlings. However, they could recover to normal growth after the herbicide effect disappeared. Butachlor greatly decreased the endogenous indole-3-acetic acid (IAA) but increased the endogenous abscisic acid (ABA) contents of rice seedlings. Addition of lAA into growth medium (Hoagland's solution) partly relieved growth inhibition. Pretreatment of both gibberellic acid ($GA_3$) and IAA 24 hours before butachlor treatment almost completely alleviated the butachlor-interfere with GA and/or IAA metabolism or their action resulting in the growth inhibition of rice. Butachlor was readily absorbed by rice roots. During 24 hours of uptake experiment, 32% of the applied herbicide was absorbed. Pretreatment of the herbicide for 2 days did ncx affect the absorption. Of the absorbed herbicide, 80% remained in roots, only 20% transported into shoots, and more than 50% was metabolized to water soluble substances. Thin-layer chromatographic (TLC) analysis indicated that the Rf value of the most abundant metabolite was butachlor-glutathione conjugate. Rice, barnyardgrass (Echinochloa crus-galli (L.) Beauv.), and monochoria (Monochoria vaginalis Presl) seedlings contained relatively high level of non-protein thiols, while the glutathione S-transferase (GST) activity was found highest in rice, barnyardgrass the next, monochoria the lowest. The difference in GST activity among these species might be related to their sensitivity to butachlor.

• Biomedical Science Letters
• /
• v.4 no.1
• /
• pp.1-9
• /
• 1998

A Corynebacterium diphtheriae iron-repressible gene dirA, that was homologous to TSA of Saccharomyces cerevisiae and AhpC subunit of Salmonella typhimurium alkyl hydroperoxide reductase, was amplified with PCR and expressed in E. coli. The DirA purified from the transformed E. coli crude extracts prevented the inactivation of enzyme caused by metal-catalyzed oxidation (MCO) system containing thiols but not by ascorbate/Fe$^{3+}$/$O_2$ MCO system. The DirA concentration, which inhibited the inactivation of glutamine synthetase by 50% (IC$_{50}$) against MCO system, was 0.12 mg/ml. The multimeric forms of DirA were converted to the monomeric form in SDS-PAGE under the thioredoxin system comprised of NADPH, Saccharomyces cerevisiae thioredoxin reductase, and thioredoxin. Also, DirA showed thioredoxin dependent peroxidase activity. All of these results were consistent with the characteristics of a thiol specific antioxidant (TSA) protein having two conserved cysteine residues.