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Detoxification Mechanism (detoxification + mechanism)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Evidence for quorum sensing in Clostridium botulinum 56A

LETTERS IN APPLIED MICROBIOLOGY, Issue 1 2006
L. Zhao
Abstract Aims:, Experiments were designed to detect quorum-sensing signals produced by Clostridium botulinum. Methods and Results:,Clostridium botulinum 56A cell-free supernatants obtained at the end of lag phase, the mid-exponential phase and early stationary phase of growth were assayed for bioluminescence in the Vibrio harveyi quorum-sensing assay system. Twelve and 16-h culture supernatants induced bioluminescence in the auto-inducer 2 (AI-2) but not the auto-inducer 1 (AI-1) assay. Intra-species quorum sensing was also assayed as the ability of the supernatants to promote spore germination and outgrowth in a microtitre plate system. Spore populations exposed to C. botulinum supernatant from the end of lag phase became positive for growth sooner than controls. Conclusions:, The influence of cell-free supernatant on ungerminated spores and detection of bioluminescence in the AI-2 assay are evidence for a signalling molecule(s) and provide a first step in characterizing C. botulinum quorum sensing. Significance and Impact of the Study:, This study suggests that spores do not behave independently of each other and may explain the inocula size effects observed in challenge studies. Whether AI-2 production in C. botulinum serves as an inter-species signal or as a detoxification mechanism remains to be determined. [source]

Ascorbate-dependent hydrogen peroxide detoxification and ascorbate regeneration during germination of a highly productive maize hybrid: Evidence of an improved detoxification mechanism against reactive oxygen species

PHYSIOLOGIA PLANTARUM, Issue 1 2000
Laura De Gara
Ascorbate content and the activities of some key enzymes involved in the detoxification from reactive oxygen species were investigated in germinated embryos of two Zea mays L. inbred lines (B73 and Mo17) and of their heterotic F1 hybrid (B73×Mo17). The F1 hybrid showed a higher ascorbate biosynthetic capability owing to a higher activity of l -galactono- , -lactone dehydrogenase (EC 1.6.5.4), the last enzyme in ascorbate biosynthesis. Ascorbate peroxidase (EC 1.11.1.11), ascorbate free radical reductase (EC 1.6.5.4) and dehydroascorbate reductase (EC 1.8.5.1) activities were much higher in the F1 hybrid than in either inbred line, whereas catalase (EC 1.11.1.6) activity was similar in the three genotypes. Native polyacrylamide gel electrophoresis (PAGE) analysis showed three forms of cytosolic ascorbate peroxidase, both in parental lines and in the F1 hybrid. On the other hand, a complex pattern of proteins with dehydroascorbate reductase activity was observed, with the hybrid combining the different dehydroascorbate-reducing proteins expressed by the inbred lines. The possible involvement of the enzymes of the ascorbate system in the phenomenon of hybrid vigour is discussed. [source]

Phytochelatin synthesis plays a similar role in shoots of the cadmium hyperaccumulator Sedum alfredii as in non-resistant plants

PLANT CELL & ENVIRONMENT, Issue 8 2010
ZHONG-CHUN ZHANG
ABSTRACT Phytochelatin (PC) synthesis is considered necessary for Cd tolerance in non-resistant plants, but roles for PCs in hyper-accumulating species are currently unknown. In the present study, the relationship between PC synthesis and Cd accumulation was investigated in the Cd hyperaccumulator Sedum alfredii Hance. PCs were most abundant in leaves followed by stems, but hardly detected by the reversed-phase high-performance liquid chromatography (HPLC) in roots. Both PC synthesis and Cd accumulation were time-dependent and a linear correlation between the two was established with about 1:15 PCs : Cd stoichiometry in leaves. PCs were found in the elution fractions, which were responsible for Cd peaks in the anion exchange chromatograph assay. About 5% of the total Cd was detected in these elution fractions as PCs were found. Most Cd was observed in the cell wall and intercellular space of leaf vascular cells. These results suggest that PCs do not detoxify Cd in roots of S. alfredii. However, like in non-resistant plants, PCs might act as the major intracellular Cd detoxification mechanism in shoots of S. alfredii. [source]

Adaptation of Medicago sativa cv. Gabès to long-term NaCl stress

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2005
Néziha Boughanmi
Abstract The perennial Medicago sativa cv. Gabès is widely grown on saline soils in Tunisian oases. The mechanisms by which this NaCl-tolerant cultivar maintains a positive growth balance were analyzed. In this plant of considerable agronomic interest, biochemical analyses were conducted in order to study the effects of salinity on mature leaves. Free-radical detoxification mechanisms and changes induced by the accumulation of reactive oxygen species (ROS) in response to the NaCl stress were compared between the upper (young) and lower (old) carbohydrate source leaves. Long-term NaCl (150 mM) treatment significantly reduced the size of source leaves supporting growth. Salinity damage was greater in the lower than in the upper leaves. This damage was associated with a high Na+ : K+ ratio and a decrease in the activity of H2O2 -scavenging enzymes, leading to lipid peroxidation. In lower source leaves that were mainly affected by ionic stress, superoxide dismutase (SOD) was overexpressed and guaiacol peroxidase (GPX) activity increased. In contrast, in upper source leaves that were mainly exposed to water deficit, catalase and ascorbate peroxidase (APX) activities increased whereas GPX activity was unchanged. The upper source leaves maintained adequate ionic and water status and an efficient ROS detoxification, allowing sinks to be supplied with photoassimilates and maintaining a positive growth balance in this cultivar of alfalfa. Anpassung von Medicago sativa cv. Gabès an Langzeit-Salzstress Die perennierende Art Medicago sativa, Sorte "Gabès", wird verbreitet auf Salzböden in tunesischen Oasen angebaut. Die Mechanismen, die eine positive Wachstumsbilanz in dieser NaCl-toleranten Luzernensorte gewährleisten, wurden untersucht. In dieser agronomisch außerordentlich wichtigen Pflanze wurden biochemische Analysen durchgeführt, um Salzeffekte auf ausgewachsene Blätter zu bestimmen. Die Mechanismen zur Entgiftung freier Radikale (ROS) und die durch die ROS verursachten Veränderungen wurden in jungen und alten "Source"-Blättern vergleichend unter Salzstressbedingungen untersucht. Eine andauernde Behandlung mit NaCl (150 mM) führte zu einer signifikanten Reduzierung der Blattfläche, wobei diese Abnahme deutlicher an den älteren unteren als an den oberen jüngeren Blättern war. Sie ging einher mit einem hohen Na+:K+ -Verhältnis und einer Abnahme der Aktivität der H2O2 -abbauenden Enzyme, was zu einer Peroxidation von Lipiden führte. Besonders in den unteren "Source"-Blättern führte der Ionenstress zu einer Überexprimierung der Superoxid-Dismutase (SOD) und einer Zunahme der Guaiakol- Peroxidaseaktivität (GPX). Demgegenüber nahmen in den oberen "Source"-Blättern, die starkem Wasserdefizit ausgesetzt waren, die Aktivitäten von Katalase und Ascorbat-Peroxidase (APX) zu, während die GPX-Aktivität unverändert blieb. Die oberen "Source"-Blätter waren in der Lage, einen adäquaten Ionen- und Wasserzustand mit Hilfe einer effizienten ROS-Entgiftung aufrechtzuerhalten, und somit einen Rückgang der Bereitstellung von Photoassimilaten zu kompensieren. Dadurch wurde eine positive Wachstumsbilanz in dieser Luzernensorte unter Salinität gewährleistet. [source]