Degradation of aromatic compounds in plants grown under aseptic conditions

The aim of the work is to investigate the ability of higher plants to absorb and detoxify environmental pollutants - aromatic compounds via aromatic ring cleavage. Transformation of 14C specifically labelled benzene derivatives, [1-6-14C]-nitrobenzene, [1-6-(14)C]-aniline, [1-(14)C]- and [7-(14)C]-benzoic acid, in axenic seedlings of maize (Zea mays L.), kidney bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) and pumpkin (Cucurbita pepo L.) were studied. After penetration in plants, the above xenobiotics are transformed by oxidative or reductive reactions, conjugation with cell endogenous compounds, and binding to biopolymers. The initial stage of oxidative degradation consists in hydroxylation reactions. The aromatic ring can then be cleaved and degraded into organic acids of the Krebs cycle. Ring cleavage is accompanied by 14CO2 evolution. Aromatic ring cleavage in plants has thus been demonstrated for different xenobiotics carrying different substitutions on their benzene ring. Conjugation with low molecular peptides is the main pathway of aromatic xenobiotics detoxification. Peptide conjugates are formed both by the initial xenobiotics (except nitrobenzene) and by intermediate transformation products. The chemical nature of the radioactive fragment and the amino acid composition of peptides participating in conjugation were identified.     

Biological interactions of alpha,beta-unsaturated aldehydes

This article describes the chemical nature of alpha,beta-unsaturated aldehydes and some of their toxicological effects based on their ability to function as direct-acting alkylating agents. Selected compounds discussed include alpha,beta-unsaturated aldehydic environmental pollutants, metabolites of xenobiotics and natural products, and lipid peroxidation--and DNA oxidation products derived from cellular constituents. Briefly reviewed are sources and mechanisms of formation of the aldehydes, their reactivity with respect to glutathione and amino-groups, their toxicity based on interaction with sulfhydryl and amino targets in cells, and modulation of their toxicity by metabolism.     

Effects of yo-yo diet, caloric restriction, and olestra on tissue distribution of hexachlorobenzene

Chlorinated hydrocarbons are lipophilic, toxic, and persistent in the environment and animal tissues. They enter the body in food and are stored in adipose tissue. Loss of body fat through caloric restriction mobilizes stored lipophilic xenobiotics and results in distribution to other tissues. We have studied the reversibility of this process in mice that followed a regimen of body weight cycling. Weight gain was followed by weight loss, a second gain, and a second loss ("yo-yo diet regimen"). We measured the distribution of orally gavaged [14C]hexachlorobenzene, which is sparingly metabolized. We found that weight cycling has different effects in different organs. Continued weight loss resulted in a threefold increase of 14C amount and concentration in the brain. After weight regain, 14C in the brain decreased but then increased again after a second weight loss. Weight loss resulted in an increase in the concentration of 14C in adipose tissue without changing the total amount in that tissue. Weight loss and regain resulted in an increase of 14C in the liver, which reflected an increase of fat in the liver. The regimen of weight gain and loss was repeated in mice gavaged with [14C]hexachlorobenzene, with one group receiving the nonabsorbable fat olestra in the diet. Combined dietary olestra and caloric restriction caused a 30-fold increase in the rate of excretion of 14C relative to an ad libitum diet or a reduced caloric diet alone. Distribution of 14C into the brain resulting from the restricted diet was reduced by 50% by dietary olestra.     

Remodeling and Sorting Process of Ethanolamine and Choline Glycerophospholipids During Their Axonal Transport in the Rabbit Optic Pathway

The existence of a mechanism by which the ester- and ether-linked aliphatic chains of the major phospholipids are retailored during their axonal transport and sorted to specific membrane systems along the optic nerve and tract was investigated. A mixture of [1-14C]hexadecanol and [3H]arachidonic acid was injected into the vitreous body of albino rabbits. At 24 h and 8 days later, the distribution (as measured by the 3H/14C ratio) and the positioning (as monitored by hydrolytic procedures) of radioactivity in the various phospholipid classes of retina, purified axons, and myelin of the optic nerve and tract were determined. At the two intervals after labeling, the 3H/14C ratios of each diradyl type of phosphatidylethanolamine and phosphatidylcholine were (a) substantially unchanged all along the axons within the optic nerve and tract and (b) markedly modified in comparison with those found in the retina and axons for molecular species selectively restricted to myelin sheath. Evidence is thus available that intraxonally moving ethanolamine and choline glycerophospholipids, among others, are added to axonal membranes most likely without extensive modifications. In contrast, they are transferred into myelin after retailoring. Through these two processes, the sorting and targeting of newly synthesized phospholipids to their correct membrane domains, such as axoplasmic organelles, axolemma, or periaxonal myelin, could be controlled.     

Novel single nucleotide polymorphisms of organic cation transporter 1 (SLC22A1) affecting transport functions

Organic cation transporter OCT1 (SLC22A1) plays an essential role in absorption, distribution, and excretion of various xenobiotics including therapeutically important drugs. In the present study, we analyzed the functional properties of the single nucleotide polymorphisms (SNPs) in SLC22A1 gene found in Japanese control individuals. Four mutations resulting in the amino acid changes (F160L, P283L, R287G, and P341L) were functionally characterized in Xenopus oocyte expression system. Two new SNPs, identified in Japanese population, P283L and R287G exhibited no uptake of both [14C]TEA and [3H]MPP+, although their protein expressions were detected in the plasma membrane of the oocytes injected with their cRNAs. Uptake of [14C]TEA by P341L was reduced to 65.1% compared to wild type, whereas F160L showed no significant change in its transport activity. This study suggests that the newly found OCT1 variants will contribute to inter-individual variations leading to the differences in cationic drug disposition and perhaps certain disease processes.     

Polychlorinated biphenyls increase fatty acid desaturation in the proliferating endoplasmic reticulum of pigeon and rat livers

1. Polychlorinated biphenyls (PCB) are abundant and persistent pollutants in the ecosystem. Commercial mixtures (e.g. Aroclor 1254) can contain up to 80 different isomers and congeners, many of which accumulate in biological systems by the ingestion of PCB-contaminated lipid components of food chains. 2. Commercial mixtures of PCB induce, in hepatic microsomal membranes in vivo, a variety of different forms of the cytochrome P-450 components of enzyme systems involved in the metabolism of drugs and other xenobiotics, and can also induce the proliferation of this membrane. Since these microsomal enzyme systems share a number of the requirements of microsomal fatty acid desaturases, we have investigated whether the induction by PCB in vivo of cytochrome-P-450-linked enzymes in the proliferating hepatic microsomal membrane of the pigeon and the rat is accompanied by increased proportions of polyunsaturated fatty acids in this membrane. 3. The most striking changes observed 120 h after treating pigeons and rats with 1.5 mmol Aroclor 1254/kg body mass were 2.2-fold and 1.6-fold increases, respectively, in the proportion of arachidonic acid in the hepatic microsomal membrane. When the effects of this treatment on the proliferation of this membrane and increase in liver mass are taken into account, the amount of arachidonic acid in the total microsomal membrane of pigeon and rat livers increased 6.7-fold and 1.9-fold, respectively. 4. These changes were accompanied by very significant increases in pigeons and rats of the concentration of hepatic microsomal cytochrome P-450, and in the activity in microsomal protein of a wide range of cytochrome P-450-dependent enzyme involved in the metabolism of drugs and other xenobiotics. 5. This effect of PCB, of increasing in vivo the degree of unsaturation of fatty acids of hepatic microsomal membrane, appears to be a novel finding, and does not seem to have been investigated for other drugs and xenobiotics. Preliminary results have shown that the effect is accompanied by substantial increases in the total activity of delta 6 and delta 5 microsomal fatty acid desaturases converting 18:2 (9, 12) (linoleic acid) to 20:4 (5, 8, 11, 14) (arachidonic acid) [Borlakoglu, J.T., Dils, R.R., Edwards-Webb, J.D. & Walker, C.H. (1988) Biochem. Soc. Trans. 16, 1072]. 6. It is postulated that there is a significant link between increased fatty acid desaturation and the induction of cytochrome-P-450-linked enzymes, and this is discussed in terms of the mechanisms involved in the metabolism of foreign compounds.     

环境污染物对水生生物产生氧化压力的分子生物标志物

为了能够建立一种简单、快速、准确的环境污染监测预警体系,人们进行了广泛的研究,其中有关环境污染物对分子生物标志物的影响已成为研究热点。生物体内的氧自由基和其它活性氧分子（ROS）对组织和细胞成分造成的伤害,称之为氧化压力,环境中的有毒物质能够对生物体产生不同程度的氧化压力。生物体内的强氧化剂或体外因素（如环境污染物）引起的强氧化物与抗氧化防御系统之间的平衡能够用于评估环境压力对生物体产生影响的程度,尤其适合于评估不同种化学物质引起氧化损伤的程度。这些抗氧化防御系统及其对氧化压力的敏感性在环境毒物学研究中占有非常重要的地位,大量研究结果表明：过渡金属、多环芳烃、有机氯和有机磷农药、多氯联苯、二氧芑和其它异型物质都能够对生物体产生氧化压力。这些有毒物质能够引起各种有害影响,如对膜脂、DNA和蛋白产生损伤;改变抗氧化酶的活性等。总结了这种氧化压力的研究进展情况,并讨论了这些分子生物标志物在水生生物中的应用。     

Lysosomal and autophagic reactions as predictive indicators of environmental impact in aquatic animals

The lysosomal-autophagic system appears to be a common target for many environmental pollutants as lysosomes accumulate many toxic metals and organic xenobiotics, which perturb normal function and damage the lysosomal membrane. In fact, lysosomal membrane integrity or stability appears to be an effective generic indicator of cellular well-being in eukaryotes: in bivalve molluscs and fish, stability is correlated with many toxicological responses and pathological reactions. Prognostic use of adverse lysosomal and autophagic reactions to environmental pollutants has been explored in relation to predicting cellular dysfunction and health in marine mussels, which are extensively used as sensitive bioindicators in monitoring ecosystem health. Derivation of explanatory frameworks for prediction of pollutant impact on health is a major goal; and we have developed a conceptual mechanistic model linking lysosomal damage and autophagic dysfunction with injury to cells and tissues. This model has also complemented the creation of a cell-based computational model for molluscan hepatopancreatic cells that simulates lysosomal, autophagic and other cellular reactions to pollutants. Experimental and simulated results have also indicated that nutritional deprivation-induced autophagy has a protective function against toxic effects mediated by reactive oxygen species (ROS). Finally, coupled measurement of lysosomal-autophagic reactions and modelling is proposed as a practical toolbox for predicting toxic environmental risk.     

Lysosomal and Autophagic Reactions as Predictive Indicators of Environmental Impact in Aquatic Animals

The lysosomal-autophagic system appears to be a common target for many environmental pollutants as lysosomes accumulate many toxic metals and organic xenobiotics, which perturb normal function and damage the lysosomal membrane. In fact, lysosomal membrane integrity or stability appears to be an effective generic indicator of cellular well-being in eukaryotes: in bivalve molluscs and fish, stability is correlated with many toxicological and pathological endpoints. Prognostic use of adverse lysosomal and autophagic reactions to environmental pollutants has been explored in relation to predicting cellular dysfunction and health in marine mussels, which are extensively used environmental sentinels. Derivation of explanatory frameworks for prediction of pollutant impact on health is a major goal; and we have developed a conceptual mechanistic model linking lysosomal damage and autophagic dysfunction with injury to cells and tissues. This model has also complemented the creation of a cell-based computational model for molluscan hepatopancreatic cells that simulates lysosomal, autophagic and other cellular reactions to pollutants. Experimental and simulated results have also indicated that nutritional deprivation - induced autophagy has a protective function against toxic effects mediated by reactive oxygen species (ROS). Finally, coupled measurement of lysosomal-autophagic reactions and modelling is proposed as a practical toolbox for predicting environmental risk.

Addendum to:

Environmental Prognostics: An Integrated Model Supporting Lysosomal Stress Responses as Predictive Biomarkers of Animal Health Status

M.N. Moore, J.I. Allen and A. McVeigh

Mar Environ Res 2005; In press     

Pollutant effects on Pacific oyster, Crassostrea gigas (Thunberg), hemocytes: Screening of 23 molecules using flow cytometry

The shellfish industry is an important economic activity in France, occurring mostly in estuarine zones subject to pollution due to anthropogenic activities. The harmful effects of pollutants on species inhabiting these estuarine zones are not well known. Among marine species, bivalve mollusks---particularly Pacific oyster, Crassostrea gigas---may serve a model of interest. The species is sedentary and filter-feeding, which favors bioaccumulation of pollutants in their tissues. Oysters may be suitable for studies on disturbance by pollutants of physiological activities, among which defense mechanisms are poorly documented in bivalves. In this study, effects of pollutants on hemocyte functions were monitored in Pacific oyster, C. gigas. Hemocytes were exposed in vitro to selected pollutants. The strategy for investigating the effects of pollutants on hemocyte functions is based on several biomarkers, which is more relevant than that of published papers based on single-endpoint experiments. Pollutants belonging to the most important groups of xenobiotics (PAHs, PCBs, and pesticides) were selected and their effect on hemocyte activities was analyzed using flow cytometry. Twenty-three pollutants were tested and eight of them showed significant modulation of hemocyte activities. PAHs and PCB 77 induced a decrease of hemocyte activity after an incubation periods of 4 and 24 h at 200 μmol/L. Three pesticides (2,4D, paraoxon, and chlorothalonil) modulated hemocyte activities. A mixture of eight pesticides also decreased phagocytotic activity. This study is one of the first to investigate the effects of so many pollutants on hemocyte functions at the same time and therefore allows a real comparison of different pollutant effects     

Temperature-dependent changes in the profile of the sarcoplasmic reticulum membrane hydrophobic zones]

The dependence of the state of the hydrophobic zone of rabbit sarcoplasmic reticulum (SR) membranes on temperature of the membrane fragment suspension before rapid freezing was studied by the freeze fracturing technique. It was shown that within the temperature range of--15-- +37 degrees C the amount of intramembrane particles and their distribution in the membrane plane and between their convex and concave surfaces do not practically depend on the temperature of the SR membrane suspension. This is indicative of the lack of correlation between the physical state of the phospholipid matrix (gel -- liquid crystal) before freezing and the nature of the profile of the membrane hydrophobic zone revealed after fracturing. The disturbances in the protein -- lipid interactions in the membrane under the effects of mersalyl or aqueous solutions of diethyl ester followed by complete inactivation of Ca2+-dependent ATPase lead to a decrease in the amount of intramembrane particles, which is especially well-pronounced at 37 degrees and -15 degrees C.     

Effect of long-term Intralipid administration in mice

Intralipid was administered intravenously to mice at a level of 2 g kg-1 day-1 for 23 days. No alterations in phagocytic index, liver or spleen size were observed in the chronically injected mice as compared with control mice that received saline injections. Tissue distribution of 0.45 micron multilamellar liposomes of egg phosphatidylcholine:cholesterol (2:1) was similar in mice that had been chronically injected with Intralipid to that in control mice. Mice chronically given the same total amount of phospholipid in the form of 0.2 micron liposomes of phosphatidylcholine:cholesterol (2:1) rather than as a lipid-triglyceride emulsion showed altered tissue distribution of entrapped label with decreased liver uptake and increased splenic uptake, which is indicative of reticuloendothelial blockade. Tissue distribution of [14C]dipalmitoylphosphatidylcholine Intralipid was compared with that of [14C]dipalmitoylphosphatidylcholine 0.2 micron MLV of phosphatidylcholine:cholesterol (2:1). Intralipid was taken up 2- to 3-fold less by liver and 5- to 10-fold less by spleen than liposomes. Blood levels of Intralipid were higher than those of liposomes. [14C]dipalmitoylphosphatidylcholine Intralipid was eliminated from the body at a faster rate than [14C]dipalmitoylphosphatidylcholine liposomes. The lack of reticuloendothelial blockade caused by Intralipid as compared with liposomes appears to be related to its diminished uptake into reticuloendothelial tissues. This diminished uptake may be related to differences in apolipoprotein uptake of Intralipid, which is primarily in the form of a phospholipid monolayer, and liposomes, which have their phospholipid organized into a bilayer.     

Identification of a novel voltage-driven organic anion transporter present at apical membrane of renal proximal tubule

A novel transport protein with the properties of voltage-driven organic anion transport was isolated from pig kidney cortex by expression cloning in Xenopus laevis oocytes. A cDNA library was constructed from size-fractionated poly(A)+ RNA and screened for p-aminohippurate (PAH) transport in high potassium medium. A 1856-base pair cDNA encoding a 467-amino acid peptide designated as OATV1 (voltage-driven organic anion transporter 1) was isolated. The predicted amino acid sequence of OATV1 exhibited 60-65% identity to those of human, rat, rabbit, and mouse sodium-dependent phosphate cotransporter type 1 (NPT1), although OATV1 did not transport phosphate. The homology of this transporter to known members of the organic anion transporter family (OAT family) was about 25-30%. OATV1-mediated PAH transport was affected by the changes in membrane potential. The transport was Na+-independent and enhanced at high concentrations of extracellular potassium and low concentrations of extracellular chloride. Under the voltage clamp condition, extracellularly applied PAH induced outward currents in oocytes expressing OATV1. The current showed steep voltage dependence, consistent with the voltage-driven transport of PAH by OATV1. The PAH transport was inhibited by various organic anions but not by organic cations, indicating the multispecific nature of OATV1 for anionic compounds. This transport protein is localized at the apical membrane of renal proximal tubule, consistent with the proposed localization of a voltage-driven organic anion transporter. Therefore, it is proposed that OATV1 plays an important role to excrete drugs, xenobiotics, and their metabolites driven by membrane voltage through the apical membrane of the tubular epithelial cells into the urine.     

Functional importance of the family 1 glucosyltransferase UGT72B1 in the metabolism of xenobiotics in Arabidopsis thaliana

The Arabidopsis type 1 UDP-glucose-dependent glucosyltransferase UGT72B1 is highly active in conjugating the persistent pollutants 3,4-dichloroaniline (DCA) and 2,4,5-trichlorophenol (TCP). To determine its importance in detoxifying xenobiotics in planta, mutant plants where the respective gene has been disrupted by T-DNA insertion have been characterized. Extracts from the knockout ugt72B1 plants showed radically reduced conjugating activity towards DCA and TCP and the absence of immunodetectable UGT72B1 protein. In contrast, activities towards phenolic natural products were unaffected. When aseptic root cultures were fed [14C]-DCA, compared with wild types, the ugt72B1 plants showed a reduced rate of uptake of the xenobiotic and very little metabolism to soluble DCA-glucose or associated polar conjugates. Instead, the knockouts accumulated non-extractable radioactive residues, most probably associated with lignification. When the feeding studies were carried out with [14C]-TCP, rates and routes of metabolism were identical in the wild type and knockouts, with TCP-glucoside a major product in both cases. Similar differential effects on the metabolism of DCA and TCP were obtained in whole plant studies with wild type and ugt72B1 mutants, demonstrating that while UGT72B1 had a central role in metabolizing chloroanilines in Arabidopsis, additional UGTs could compensate for the conjugation of TCP in the knockout. TCP was equally toxic to wild type and ugt72B1 plants, while surprisingly, the knockouts were less sensitive to DCA. From this it was concluded that the glucosylation of DCA may not be as effective in xenobiotic detoxification as bound-residue formation.     

Recent developments in biodegradation of industrial pollutants by white rot fungi and their enzyme system

Increasing discharge and improper management of liquid and solid industrial wastes have created a great concern among industrialists and the scientific community over their economic treatment and safe disposal. White rot fungi (WRF) are versatile and robust organisms having enormous potential for oxidative bioremediation of a variety of toxic chemical pollutants due to high tolerance to toxic substances in the environment. WRF are capable of mineralizing a wide variety of toxic xenobiotics due to non-specific nature of their extracellular lignin mineralizing enzymes (LMEs). In recent years, a lot of work has been done on the development and optimization of bioremediation processes using WRF, with emphasis on the study of their enzyme systems involved in biodegradation of industrial pollutants. Many new strains have been identified and their LMEs isolated, purified and characterized. In this review, we have tried to cover the latest developments on enzyme systems of WRF, their low molecular mass mediators and their potential use for bioremediation of industrial pollutants.     

Structure and functions of linkage unit intermediates in the biosynthesis of ribitol teichoic acids in Staphylococcus aureus H and Bacillus subtilis W23

The stepwise formation and characterization of linkage unit intermediates and their functions in ribitol teichoic acid biosynthesis were studied with membranes obtained from Staphylococcus aureus H and Bacillus subtilis W23. The formation of labeled polymer from CDP-[14C]ribitol and CDP-glycerol in each membrane system was markedly stimulated by the addition of N-acetylmannosaminyl(beta 1----4)N-acetylglucosamine (ManNAc-GlcNAc) linked to pyrophosphorylyisoprenol. Whereas incubation of S. aureus membranes with CDP-glycerol and ManNAc-[14C]GlcNAc-PP-prenol led to synthesis of (glycerol phosphate) 1-3-ManNAc-[14C]GlcNAc-PP-prenol, incubation of B. subtilis membranes with the same substrates yielded (glycerol phosphate)1-2-ManNAc-[14C]GlcNAc-PP-prenol. In S. aureus membranes, (glycerol phosphate)2-ManNAc-[14C]GlcNAc-PP-prenol as well as (glycerol phosphate)3-ManNAc-[14C]GlcNAc-PP-prenol served as an acceptor for ribitol phosphate units, but (glycerol phosphate)-ManNAc-[14C]GlcNAc-PP-prenol did not. In B. subtilis W23 membranes, (glycerol phosphate)-ManNAc-[14C]GlcNAc-PP-prenol served as a better acceptor for ribitol phosphate units than (glycerol phosphate)2-ManNAc-[14C]GlcNAc-PP-prenol. In this membrane system (ribitol phosphate)-(glycerol phosphate)-ManNAc-[14C]GlcNAc-PP-prenol was formed from ManNAc-[14C]GlcNAc-PP-prenol, CDP-glycerol and CDP-ribitol. The results indicate that (glycerol phosphate)1-3-ManNAc-GlcNAc-PP-prenol and (glycerol phosphate)1-2-ManNac-GlcNAc-PP-prenol are involved in the pathway for the synthesis of wall ribitol teichoic acids in S. aureus H and B. subtilis W23 respectively.     

Annexin II is the membrane receptor that mediates the rapid actions of 1alpha,25-dihydroxyvitamin D(3)

1alpha,25-Dihydroxyvitamin D(3) has been shown to exert its effects by both genomic (minutes to hours) and rapid (seconds to minutes) mechanisms. The genomic effects are mediated by interaction with the nuclear vitamin D receptor. We show that the vitamin D analog, [(14)C]-1alpha,25-dihydroxyvitamin D(3) bromoacetate, is specifically bound to a protein (molecular weight 36 kDa) in the plasma membrane of rat osteoblastlike cells (ROS 24/1). The plasma membrane protein labeled with the bromoacetate analog was identified as annexin II by sequence determination and Western blot. Partially purified plasma membrane proteins (PI 6.9-7.4) and purified annexin II exhibited specific and saturable binding for [(3)H]-1alpha, 25-dihydroxyvitamin D(3). Antibodies to annexin II inhibited [(14)C]-1alpha,25-dihydroxyvitamin D(3) bromoacetate binding to ROS 24/1 plasma membranes, immunoprecipitated the ligand-protein complex, and inhibited 1alpha,25-dihydroxyvitamin D(3)-induced increases in intracellular calcium in ROS 24/1 cells. The results indicate that annexin II may serve as a receptor for rapid actions of 1alpha, 25-dihydroxyvitamin D(3).     

Functional properties of membrane-associated complement receptor CR1

It was previously shown that membrane receptors for C3b (CR1) purified from human erythrocytes were powerful inhibitors of the complement cascade and that they encompass the regulatory functions of the serum proteins beta 1H (H) and C4-binding protein (C4bp). In the present report we study the functional properties of membrane-associated CR1. When tonsil lymphocytes, which contain between 30 and 60% of CR1-bearing B cells, are incubated with the red cell complement intermediate EAC14oxy2lim or EAC14oxy23lim, they inhibit both C42 and C423 in a dose-dependent manner. These effects are mediated by membrane-associated molecules. Indeed, mild trypsinization of the lymphocytes abolishes their activity, and formaldehyde-fixed cells are as effective as viable cells. The inhibitory effects are in part mediated by CR1. The lymphocyte activities are reversed about 60% if monoclonal antibodies to CR1 or fluid phase C3b are present in the incubation medium. Moreover, upon addition of C3b-inactivator (l), lymphocytes release C3c fragments from EAC14oxy23b. The release of C3c was also abolished by antibodies to CR1. These results support the idea that CR1, as well as other molecules from the lymphocyte membrane, can function as inhibitor(s) of complement activation in their vicinity.     

Expression of a human cytochrome P4502E1 in Nicotiana tabacum enhances tolerance and remediation of γ-hexachlorocyclohexane

Lindane (γ-hexachlorocyclohexane), a persistent organo-chlorine insecticide widely used in developing countries, has a negative effect as a polluting agent of soil and surface waters. Plants can be used for remediation of organic pollutants and their efficiency can be enhanced by introduction of heterologous genes. Mammalian cytochrome P4502E1 (CYP2E1), an important monooxygenase is involved in the degradation of a wide range of xenobiotics including environmental pollutants/herbicides and pesticides. Here, we report the development of transgenic tobacco plants expressing human CYP2E1 and the efficacy of plants for remediation of lindane. Transgenic tobacco plants with CYP2E1 showed enhanced tolerance to lindane when grown in hydroponic medium and soil compared to control plants. Remediation of (14)C-labeled lindane from hydroponic medium was higher in transgenic plants compared to that of control plants, with the best performing line showing 25% higher removal of lindane from solution than control plants. Similar results were seen in plants grown in soil spiked with lindane. The present study has shown that transgenic plants expressing CYP2E1 gene have potential use for remediation of lindane from contaminated solutions and soil.     

Genetically modified Pseudomonas biosensing biodegraders to detect PCB and chlorobenzoate bioavailability and biodegradation in contaminated soils

Whole cell microbial biosensors offer excellent possibilities for assaying the complex nature of the bioavailable and bioaccessible fraction of pollutants in contaminated soils, which currently cannot be easily addressed. This paper describes the application and evaluation of three microbial biosensor strains designed to detect the bioavailability and biodegradation of PCBs (and end-products) in contaminated soils and sediments. Polychlorinated biphenyls (PCBs) are considered to be one of the most wide spread, hazardous and persistent pollutants. Herein we describe that there was a positive correlation between the PCB levels within the samples and the percentage of biosensor cells that were expressing their reporter gene; gfp. Immobilisation of the biosensors in calcium alginate beads allowed easy and accurate detection of the biosensor strains in contaminated soil and sludge samples. The biosensors also showed that PCB degradation activity was occurring at a much greater level in Pea inoculated planted soil compared to inoculated unplanted soil indicating rhizoremediation (the removal of pollutants by plant root associated microbes) shows considerable promise as a solution for removing organic xenobiotics from the environment.