X-ray crystallographic investigation and biological activities of Ru(III) complexes containing Schiff base and triphenyl phosphine/arsine

The crystal structures of the complexes [RuCl(Nap-o-phd)(AsPh₃)] and [RuBr(Nap-o-phd)(PPh₃)] (where H₂-Nap-o-phd = N,N′-bis(2-hydroxy-1-naphthaldehyde) o-phenylenediamine) have been determined by single crystal X-ray diffraction techniques. The antibacterial properties of the complexes have also been examined.     

beta-Alanine betaine synthesis in the Plumbaginaceae. Purification and characterization of a trifunctional, S-adenosyl-L-methionine-dependent N-methyltransferase from Limonium latifolium leaves.

beta-Alanine (beta-Ala) betaine is an osmoprotective compound accumulated by most members of the highly stress-tolerant family Plumbaginaceae. Its potential role in plant tolerance to salinity and hypoxia makes its synthetic pathway an interesting target for metabolic engineering. In the Plumbaginaceae, beta-Ala betaine is synthesized by S-adenosyl-L-methionine-dependent N-methylation of beta-Ala via N-methyl beta-Ala and N,N-dimethyl beta-Ala. It was not known how many N-methyltransferases (NMTases) participate in the three N-methylations of beta-Ala. An NMTase was purified about 1,890-fold, from Limonium latifolium leaves, using a protocol consisting of polyethylene glycol precipitation, heat treatment, anion-exchange chromatography, gel filtration, native polyacrylamide gel electrophoresis, and two substrate affinity chromatography steps. The purified NMTase was trifunctional, methylating beta-Ala, N-methyl beta-Ala, and N,N-dimethyl beta-Ala. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses indicated that the native NMTase is a dimer of 43-kD subunits. The NMTase had an apparent K(m) of 45 microM S-adenosyl-l-methionine and substrate inhibition was observed above 200 microM. The apparent K(m) values for the methyl acceptor substrates were 5.3, 5.7, and 5.9 mM for beta-Ala, N-methyl beta-Ala, and N,N-dimethyl beta-Ala, respectively. The NMTase had an isoelectric point of 5.15 and was reversibly inhibited by the thiol reagent p-hydroxymercuribenzoic acid.     

Genome analysis of alginate synthesizing Pseudomonas aeruginosa strain SW1 isolated from degraded seaweeds

Antonie van Leeuwenhoek - Pseudomonas aeruginosa strain SW1 is an aerobic, motile, Gram-negative, and rod-shaped bacterium isolated from degraded seaweeds. Based on the 16S rRNA gene sequence and...     

Effects of selenium on arsenic uptake in arsenic hyperaccumulator Pteris vittata L

Selenium (Se) is a non-metallic element, which has the capability to increase the antioxidative capacity and stress tolerance of plants to heavy metals. Plants vary considerably in their physiological response to Se. The reported research investigated the effects of Se on arsenic (As) uptake by As hyperaccumulator Pteris vittata L. and determined possible mechanisms of interaction. Pteris vittata plants were exposed hydroponically to 0, 150 or 300 microM of Na(2)HAsO(4) in the presence of 0, 5 or 10 microM of Na(2)SeO(4) for 5 or 10d. Application of 5 microM Se enhanced As concentration by P. vittata fronds by 7-45%. At 5 microM, Se acted as an antioxidant, inhibiting lipid peroxidation (reduced by 26-42% in the fronds) via increased levels of thiols and glutathione (increased by 24% in the fronds). The results suggest that Se is either an antioxidant or it activates plant protective mechanisms, thereby alleviating oxidative stress and improving arsenic uptake in P. vittata.     

Formation of unusual ruthenium(III) carbonyl complex through ONS tricoordination of salicylaldehyde-N-phenylthiosemicarbazone

An unusual coordination mode of salicylaldehyde-N-phenylthiosemicarbazone (H₂-Sal-Ptsc) ligand was observed in unusual ruthenium(III) carbonyl complex for the first time when it was reacted with [RuHCl(CO)(PPh₃)₃]. The EPR and electrochemical analysis conformed the formation of Ru(III) species.     

Molecular Detection of New Delhi Metallo-Beta-Lactamase-1 (NDM-1) Positive Bacteria from Environmental and Drinking Water Samples by Loop Mediated Isothermal Amplification of blaNDM-1

New Delhi metallo-β-lactamase-1 gene (bla_NDM-1) codes for New Delhi metallo-beta-lactamase-1 (NDM-1) enzyme that cleaves the amide bond of β-lactam ring, and provides resistance against major classes of β-lactam antibiotics. Dissemination of the plasmid borne bla_NDM-1 through horizontal gene transfer is a potential threat to the society. In this study, a rapid non-culture method for detecting NDM-1 positive bacteria was developed by Loop Mediated Isothermal Amplification (LAMP) of bla_NDM-1. Sensitivity of this method was found to be one femtogram of plasmid DNA, which translates into 2.6–25.8 copies depending on the size of the plasmid DNA. This method was applied to detect NDM-1 positive bacteria in 81 water samples that were collected from environmental and drinking water sources. NDM-1 positive bacteria were detected in three drinking water samples by LAMP but not by PCR. These three samples were collected from the water sources that were treated with chlorine for decontamination before public distribution. NDM-1 positive bacteria were not detected in lake water samples or in the samples that were collected from the water sources that were purified by reverse osmosis before public distribution. Detection of NDM-1 positive bacteria using LAMP was found to be safe, sensitive and rapid for screening large number of samples from diverse sources. This method could be developed as on-field detection kit by using fluorescent dyes to visualize the amplified bla_NDM-1 gene.     

Metabolic Engineering for Stress Tolerance: Installing Osmoprotectant Synthesis Pathways

Abiotic environmental stresses such as drought, salinity andlow temperature are major limitations for plant growth and cropproductivity. Certain plants, marine algae and bacteria haveevolved a number of adaptations to such abiotic stresses: someof these adaptations are metabolic and others structural. Accumulationof certain organic solutes (known as osmoprotectants) is a commonmetabolic adaptation found in diverse taxa. These solutes protectproteins and membranes against damage by high concentrationsof inorganic ions. Some osmoprotectants also protect the metabolicmachinery against oxidative damage. Many major crops lack theability to synthesize the special osmoprotectants that are naturallyaccumulated by stress-tolerant organisms. Therefore, it washypothesized that installing osmoprotectant synthesis pathwaysis a potential route to breed stress-tolerant crops. Provingthis, recent engineering efforts in model species led to modestbut significant improvements in stress tolerance of transgenicplants. Synthetic pathways to two kinds of osmoprotectants—polyolsand quaternary ammonium compounds—are discussed here.Results from the metabolic engineering experiments emphasizethe need for a greater understanding of primary metabolic pathwaysfrom which osmoprotectant synthesis pathways branch. Futureresearch avenues include the identification and exploitationof diverse osmoprotectants in naturally stress-tolerant organisms,and the use of multiple genes and reiterative engineering toincrease osmoprotectant flux in response to stress. High-throughputgenomic technologies offer a number of tools to refine thisby rapidly identifying genes, pathways, and regulatory controls.Copyright 2000 Annals of Botany Company Review, abiotic stress, osmoprotectant, compatible solute, genetic engineering     

Conversion of membrane lipid acyl groups to triacylglycerol and formation of lipid bodies upon nitrogen starvation in biofuel green algae Chlorella UTEX29

Algal lipids are ideal biofuel sources. Our objective was to determine the contributors to triacylglycerol (TAG) accumulation and lipid body formation in Chlorella UTEX29 under nitrogen (N) deprivation. A fivefold increase in intracellular lipids following N starvation for 24 h confirmed the oleaginous characteristics of UTEX29. Ultrastructural studies revealed increased number of lipid bodies and decreased starch granules in N-starved cells compared to N-replete cells. Lipid bodies were observed as early as 3 h after N removal and plastids collapsed after 48 h of stress. Moreover, the identification of intracellular pyrenoids and differences in the expected nutritional requirements for Chlorella protothecoides (as UTEX29 is currently classified) led us to conduct a phylogenetic study using 18S and actin cDNA sequences. This indicated UTEX29 to be more phylogenetically related to Chlorella vulgaris. To investigate the fate of different lipids after N starvation, radiolabeling using ¹⁴C-acetate was used. A significant decrease in ¹⁴C-galactolipids and phospholipids matched the increase in ¹⁴C-TAG starting at 3 h of N starvation, consistent with acyl groups from structural lipids as sources for TAG under N starvation. These results have important implications for the identification of key steps controlling oil accumulation in N-starved biofuel algae and demonstrate membrane recycling during lipid body formation.     

Transgenic expression of fern Pteris vittata glutaredoxin PvGrx5 in Arabidopsis thaliana increases plant tolerance to high temperature stress and reduces oxidative damage to proteins

A glutaredoxin of the fern Pteris vittata PvGRX5 was previously implicated in arsenic tolerance. Because of possible involvements of glutaredoxins in metabolic adaptations to high temperature stress, transgenic Arabidopsis lines constitutively expressing PvGRX5 were evaluated for thermotolerance. Homozygous lines expressing PvGRX5 exhibited significantly greater tolerance to high temperature stress than the vector control and wild-type, based upon growth during stress and during recovery from stress, and this was related to leaf glutaredoxin specific activities. Measurements of tissue ion leakage, thiobarbituric acid reactive substances and protein carbonyl content showed that PvGRX5-expressors were significantly (P < 0.05) less affected by the high temperature treatment compared to wild-type and vector control lines for damage to membranes and proteins. Immunoblots indicated that specific protein bands, carbonylated during the stress treatment in the control lines, were protected in PvGRX5-expressors, thus implicating PvGRX5 in heat tolerance, likely mediated through cellular protection against oxidative stress.     

Effects of nutrients on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

This research investigated the effects of various nutrients on arsenic (As) removal by arsenic hyperaccumulator Pteris vittata L. in a Hoagland nutrient solution (HNS). The treatments included different concentrations of Ca and K in 20% strength of HNS, different strengths of HNS (10, 20 and 30%), different strengths of HNS (10 and 20%) with and without CaCO₃, and different concentrations of Ca, K, NO₃, NH₄, and P in 20% strength of HNS. The plants were grown in nutrient solution containing 1 mg As L^?1 for 4 weeks except the Ca/K experiment where the plants were grown in nutrient solution containing 10 or 50 mg As L^?1 for 1 week. Adding up to 4 mM Ca or 3 mM K to 20% strength HNS significantly (P < 0.05) increased plant arsenic accumulation when the solution contained 10 mg As L^?1. Plant arsenic removal was reduced with increasing Ca and K concentrations at 50 mg As L^?1. Lower strength of HNS (10%) resulted in the greatest plant arsenic removal (79%) due to lower competition of P with As for plant uptake. Addition of CaCO₃ to 20% strength of HNS significantly increased arsenic removal by P. vittata. Among the nutrients tested, NO₃ and CaCO₃ were beneficial to plant arsenic removal while NH₄, P and Cl had adverse effects. This experiment demonstrated that it is possible to optimize plant arsenic removal by adjusting nutrients in the growth medium.