秋茄(Kandelia candel)幼苗对多氯联苯污染的生理生态响应

通过盆栽实验,研究了4种不同浓度（180、900、1800和2700μg kg^-1）的多氯联苯（PCBs）对红树植物秋茄幼苗的茎高、茎径、生物量、相对生长速率以及叶片的叶绿素含量、水势、丙二醛含量和游离脯氨酸含量等生理生态指标的影响,结果表明：（1）在所设PCBs浓度范围内,PCBs对秋茄幼苗的茎高、茎径、生物量和相对生长速率等生长指标的生长没有产生不利的影响,相反具有促进作用,红树植物秋茄在PCBs污染情况下能旺盛生长;（2）在所设PCBs浓度范围内,秋茄幼苗叶片能保持相对正常的叶绿素水平和相对稳定的叶绿素a／b值,叶绿素a、叶绿素b和叶绿素a＋b的含量虽然有所降低,但均为对照的70％以上;叶绿素a／b值有所升高,但均未超过对照的15％。（3）随着PCBs浓度的升高,秋茄幼苗叶片水势呈上升趋势,而游离脯氨酸含量和膜质过氧化产物MDA含量均有一定的增加,说明PCBs对秋茄幼苗产生了一定的影响。总体来看,秋茄幼苗能在所设浓度的PCBs范围内正常生长,对PCBs有较强的耐受性和适应性,对PCBs污染的沉积物进行修复是可行的。     

The effect of polychlorinated biphenyls (PCBs) on the membrane lipids of Pseudomonas stutzeri

In this study we examined the effect of polychlorinated biphenyls (PCBs) on biomass production of a PCB-degrading Pseudomonas stutzeri, and on the fatty acid profile of its major membrane lipids. Growth based on biomass weight was stimulated when PCBs were added at the time of inoculation, but PCB addition three days after inoculation led to a significant decrease in biomass. Simultaneous addition of PCBs plus biphenyl or PCBs plus carvone negatively affected P. stutzeri biomass (addition of biphenyl or carvone at the time of inoculation and PCBs to three-day-old culture). In the presence of PCBs alone the amount of the prevalent fatty acids C16:0 and C17-cyclopropyl fatty acid (C17-CP) of P. stutzeri in total and neutral lipids was significantly reduced. When PCBs were added together with carvone (carvone at the time of inoculation and PCBs after three days) a significant reduction of these fatty acids was obtained, but, in addition, oleic, cis-vaccenic, and cyclononadecanic (C19-CP) acids were increased. When PCBs were combined to biphenyl the prevalent fatty acids were reduced and oleic, cis-vaccenic, and cyclononadecanic acids were increased in total and neutral lipids. Addition of 3-chlorobenzoic acid led to a significant growth inhibition and to the production of oleic and cis-vaccenic acids in the membrane fraction phosphatidylcholine.     

Potential importance of protozoan grazing on the accumulation of polychlorinated biphenyls (PCBs) in the pelagic food web

Experiments were conducted to study the distribution of three selectedpolychlorinated biphenyl (PCB) congeners within the microbial food web attwo different nutrient levels; control and nutrient enriched. The objectivewas to quantify the uptake of PCBs through grazing by protozoa. The¹⁴C-PCBs tested were 4-chlorobiphenyl (IUPAC # 3),2,2,5,5-tetrachlorobiphenyl (IUPAC # 52), and2,2,4,4,5,5-hexachlorobiphenyl (IUPAC # 153). EachPCB was incubated in triplicate seawater samples at 20 idref;Cover one week. Daily, samples were separated into four fractions; <0.2µm (dissolved), 0.2-2 µm (bacteria), 2-10 µm(flagellate), and > 10 µm (microplankton; phytoplankton andprotozoa) by selective filtration. Of the PCB fraction that initiallyadsorbed to particles, 60–100% was associated to the bacterialfraction and 0–5% to the microplankton fraction. The totaluptake was highest in the nutrient enriched samples, but when normalized tothe carbon biomass the concentration was lower or equal to the control inall particle fractions. The recovery of the PCBs in the particulatefractions depended on the degree of chlorination, as the highest values wereobserved for the 2,2,4,4,5,5-hexachlorobiphenyl and thelowest for the 4-chlorobiphenyl. The concentrations in the bacterial andflagellate fractions decreased over the first 48–96 hours whilst theconcentration increased in the highest trophic level (>10 µmfraction). Approximately 75% of the increase in concentration of the2,2,4,4,5,5-hexachlorobiphenyl in the > 10 µmfraction was estimated to be the result of bacterivory. Our results indicatethe microbial food web can contribute to a rapid uptake of higherchlorinated PCBs, particularly in oligotrophic ecosystems where thebacterial biomass dominates.     

The nature of the cellulose-binding domain effects the activities of a bacterial endoglucanase on different forms of cellulose

Abstract The hybrid Pseudomonas cepacia strain JHR22 was tested for its ability to degrade Aroclor 1221 in soil. The influence of supplements—mineral salts and trace elements—on the degradation was investigated. Disapperance of Aroclor 1221 congeners, occurence of metabolites, and release of chloride were measured under different conditions. After 45 days the hybrid organism, strain JHR22, was still present at high numbers in soil, independently of whether the soil had been sterilized prior to inoculation or not. There was only a minor difference in degradation efficiency between sterilized and untreated soil with about 70% release of chloride when 10⁷ cells/g soil were inoculated. The whole hybrid pathway, originating from three different strains, was found to be stable under the conditions tested. Mineral salts did not significantly affect the degradation rate or survival of the hybrid strain.     

A DNA module encoding bph genes for the degradation of polychlorinated biphenyls (PCBs)

Abstract In this report we describe the development and construction of a DNA module which encodes bph genes for the metabolism of PCBs and which is capable of stable integration into the chromosome of Gram negative bacteria. Introduction of the bph -module into Pseudomonas putida KT2442, Pseudomonas sp. strain B13 and its genetically engineered derivative B13FR1 expanded the biodegradative ability of these strains to include biphenyl and 4-chlorobiphenyl. The bph operon was stably inherited under laboratory conditions. Behavior of the genetically engineered strains was evaluated under simulated natural habitat conditions in lake sediment microcosms with respect to survival and removal of 4-chlorobiphenyl. The genetically engineered strains persisted under these conditions and were effective in degrading 4-chlorobiphenyl over a five day incubation period.     

Biodegradation of polychlorinated biphenyls in Aroclor 1232 and production of metabolites from 2,4,4'-trichlorobiphenyl at low temperature by psychrotolerant Hydrogenophaga sp. strain IA3-A

AIMS: To determine the extent and pattern of degradation of polychlorinated biphenyls (PCBs) in Aroclor 1232 at 5 degrees C by a psychrotolerant bacterium, and to confirm the formation of intermediates of PCB metabolism at low temperature using 2,4,4'-trichlorobiphenyl (2,4,4'-TCB). METHODS AND RESULTS: 10 ppm of Aroclor 1232 or 100 micromol l(-1) 2,4,4'-TCB was incubated with biphenyl-grown cells at 5 degrees C or 30 degrees C for 48 or 72 h. Degradation of PCBs and the products of metabolism of 2,4,4'-TCB were confirmed by gas chromatography and mass spectrometry. Extents of degradation of many of the PCBs were similar at 5 degrees C and 30 degrees C. The extent of biodegradation of PCBs in Aroclor 1232 at 5 degrees C was dependent on chlorination pattern. The 14 chlorine-containing intermediates of 2,4,4'-TCB metabolism, which were detected, include several isomers of dihydrodiols, dihydroxy compounds and meta-cleavage compounds. CONCLUSIONS: The bacterium will be useful for bioremediation of PCB-contaminated sites in cold climates; however, knowledge of the products of PCB metabolism is necessary, as they could be more toxic than the parent compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: Substantial degradation of some PCBs in Aroclor 1232 was demonstrated at low temperature within 48 h. The detection of several isomeric intermediates suggests that multiple pathways are used to transform PCBs in this strain. For the first time, formation of metabolic products from 2,4,4'-TCB at low temperature is confirmed.     

Specific biodegradation of polychlorinated biphenyls (PCBs) facilitated by plant terpenoids

The aim of this study was to examine how plant terpenoids, as natural growth substrates or inducers, would affect the biodegradation of PCB congeners. Various PCB degraders that could grow on biphenyl and several terpenoids were tested for their PCB degradation capabilities. Degradation activities of the PCB congeners, 4,4′-dichlorobiphenyl (4,4′-DCBp) and 2,2′-dichlorobiphenyl (2,2′-DCBp), were initially monitored through a resting cell assay technique that could detect their degradation products. The PCB degraders,Pseudomonas sp. P166 andRhodococcus sp. T104, were found to grow on both biphenyl and terpenoids ((S)-(−) limonene,p-cymene and α-terpinene) whereasArthrobacter sp. B1B could not grow on the terpenoids as a sole carbon source. The B1B strain grown on biphenyl exhibited good degradation activity for 4,4′-DCBp and 2,2′-DCBp, while the activity of strains P166 and T104 was about 25% that of the B1B strain, respectively. Concomitant GC analysis, however, demonstrated that strain T104, grown on (S)-(−) limonene,p-cymene and α-terpinene, could degrade 4,4′-DCBp up to 30%, equivalent to 50% of the biphenyl induction level. Moreover, strain T104 grown on (S)-(−) limonene, could also degrade 2,2′-DCBp up to 30%. This indicates that terpenoids, widely distributed in nature, could be utilized as both growth and/or inducer substrate(s) for PCB biodegradation in the environment.     

Determination of the rotational barriers of atropisomeric polychlorinated biphenyls (PCBs) by a novel stopped-flow multidimensional gas chromatographic technique

The rotational barriers ΔG^‡ (T) of the four atropisomeric polychlorinated biphenyls (PCBs) 2,2′,3,5′,6-pentachlorobiphenyl (PCB 95), 2,2′3,3′,4,6′-hexachlorobiphenyl (PCB 132), 2,2′,3,3′,6,6′-hexachlorobiphenyl (PCB 136), and 2,2′,3,4′,5′,6-hexachlorobiphenyl (PCB 149) were determined via on-line enantiomerization kinetics by a new stopped-flow multidimensional gas chromatographic technique (stopped-flow MDGC) employing Chirasil-Dex as chiral stationary phase for enantiomer separation. The calculated rotational barriers ΔG^‡ (T) of the trichloro-ortho-substituted atropisomers are 184 ± 2 kJ/mol for PCB 95, 189 ± 4 kJ/mol for PCB 132, and 184 ± 1 kJ/mol for PCB 149 at 300°C. The rotational barrier ΔG^‡ (T) of tetrachloro-ortho-substituted PCB 136 is at least (or higher than) 210 kJ/mol at 320°C. Chirality 10:316–320, 1998. © 1998 Wiley-Liss, Inc.     

Cometabolic degradation of polychlorinated biphenyls (PCBs) by axenic cultures of Ralstonia sp. strain SA-5 and Pseudomonas sp. strain SA-6 obtained from Nigerian contaminated soils

Substantial metabolism of 2,3,4,5-tetrachlorobiphenyl (2,3,4,5-tetraCB) and 2,3′,4′,5-tetraCB by axenic cultures of Ralstonia sp. SA-5 and Pseudomonas sp. SA-6 was observed in the presence of biphenyl supplementation, although, the strains were unable to utilize tetrachlorobiphenyls as growth substrate. The former was more amenable to aerobic degradation (∼70% degradation) than the latter (22–45% degradation). Recovery of 2,5-chlorobenzoic acid and chloride from 2,3′,4′,5-tetraCB assay is an indication of initial dioxygenase attack on the 3,4-dichlorophenyl ring. The PCB-degradative ability of both strains was also investigated by GC analysis of individual congeners in Aroclor 1242 (100 ppm) following 12-day incubation with washed benzoate-grown cells. Results revealed two different catabolic properties. Whereas strain SA-6 required biphenyl as inducer of the degradation activity, such induction was not required by strain SA-5. Nearly all the detectable congeners in the mixture were extensively degraded (% reduction in ECD area counts for individual congeners ranged from 50.0 to 100% and 14.2 to 100%, respectively, for SA-5 and SA-6). The two strains exhibited no noticeable specificity for congeners with varying numbers of chlorine substitution and positions. The degradative competence of these isolates most especially SA-5 makes them among the most versatile PCB-metabolizing organisms yet reported.     

Effect of nutrient enrichment on the distribution and sedimentation of polychlorinated biphenyls (PCBs) in seawater

The effect of nutrient enrichment on the distribution of polychlorinated biphenyl's (PCBs) in the microbial food web and the residence time of PCBs in seawater was studied in an experimental mesocosm system. Two 5 m high temperature and light controlled mesocosm tubes (⊘ = 0,5 m) were filled with seawater from the northern Baltic Sea. Inorganic phosphorus and nitrogen were added daily to one mesocosm, while the other served as a control. Experiments were conducted at 5, 10 and 20°>C. Three ¹⁴C-labelled PCBs of different degree of chlorination were added to subsamples of the mesocosms: 4 chlorobiphenyl (MCB), IUPAC # 3; 2,2′,5,5′-tetrachlorobiphenyl (TCB), IUPAC # 52 and 2,2′, 4,4′,5,5′-hexachlorobiphenyl (HCB) IUPAC # 153. The biomasses and growth rates of the microorganisms as well as the sedimentation rate of particulate organic material increased with nutrient enrichment. The size distribution of the microorganisms changed with nutrient status, from dominance of picoplankton (< 2 μm) in the control towards increased importance of micro (> 10 μm) and nanoplankton (2– 10 μm) in nutrient enrichment. The specific growth rate of the bacterial community was found to be more temperature dependent than that of the phytoplankton community. The relative proportion of PCBs in the >2 μm fraction was observed to be in the order MCB < TCB < HCB, while the opposite distribution prevailed in the < 2 μm fraction. We hypothesize that this is due to the combined effect of the different Kow values of the PCBs and a different composition of the particulate organic carbon in the > 2 μm and < 2 μm fractions (e.g. different lipid composition). The residence time of the PCBs in the mesocosm generally decreased with nutrient enrichment, but was dependent on the degree of chlorination of the PCB. Our results indicate that the transport of organic pollutants up through the food web is more important in nutrient poor than in nutrient rich waters and that the importance of sedimentation is higher in eutrophic ecosystems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of chlorobenzoates on the degradation of polychlorinated biphenyls (PCB) by Pseudomonas stutzeri

Chlorobenzoic acids (CBA) are frequently dead-end products of partial aerobic biodegradation of polychlorinated biphenyls (PCB). When CBA produced from PCB accumulate in the growth medium, they can inhibit the bacterial growth and consequently, slow down PCB biodegradation. In this study, the effects of seven mono- and dichlorinated CBA on growth of Pseudomonas stutzeri on different substrates and on the PCB degradation by this strain in a liquid mineral medium were tested. 3-CBA was the strongest growth inhibitor for P. stutzeri growing on glucose, benzoate and biphenyl. It was found to inhibit heavily the elimination of some di- and trichlorinated biphenyls. In contrast, its influence on the elimination of more chlorinated congeners was much less significant.The authors are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Technical University, 812 37 Bratislava, Slovakia.     

Effect of polychlorinated biphenyls (PCBs) on basal and OT-stimulated calcium concentrations in myometrial cells in cows

We investigated the effect of PCB-77, -126 or -153 (10 or 100 ng/ml) on free intracellular calcium concentrations([Ca2+]i) in bovine myometrial cells from days 1-5 of the estrous cycle. Cells were incubated with or without PCBs for 48 h (38 degrees C, aerated atmosphere) and thereafter [Ca2+]i was measured by means of fluorescent calcium indicator Fura-2. PCBs increased basal concentrations of [Ca2+]i measured before oxytocin (OT) challenge. The increase in [Ca2+]i in cells incubated with PCBs and challenged with OT was inhibited or delayed when compared to control OT-stimulated cells (p<0.05). The applied doses of PCBs did not affect viability of myometrial cells. In conclusion, the influence of PCBs upon intracellular calcium mobilization in myometrial cells impaired the bovine uterus contractility.     

Effects of two prototypic polychlorinated biphenyls (PCBs) on lipid composition of rat liver and serum

Mature male Sprague-Dawley rats received a single IP injection of either 2,2',4,4',5,5'-hexachlorobiphenyl (HCB), 3,3',4,4'-tetrachlorobiphenyl (TCB) (300 microm/kg) in corn oil (10 ml/kg) or the corn oil vehicle alone, and were killed four days later after having been fasted overnight. The vehicle control group consisted of rats which were allowed free access to feed as well as pair-fed animals. Lipid analyses were conducted on liver, hepatic microsomes and serum. TCB- (but no HCB-) treatment resulted in a statistically significant increase in total liver lipids and triglycerides. Liver phospholipids remained unchanged. Both PCBs increased the cholesterol and phospholipids content of the liver microsomal fraction. Serum lipids measured were not statistically different from control values. While HCB had little effect on the fatty acid composition of liver lipids, TCB caused an increase in C 18:1 (n-9) and a decrease in C 20:4 (n-6). Both PCBs increased C 18:0 in the hepatic microsomal fraction, but TCB also decreased C 16:0. Neither PCB altered the fatty acid composition of serum total lipids. These data are consistent with the concept that specific alterations in lipid metabolism are dependent on the structure of the PCB.     

Plant terpenes and lignin as natural cosubstrates in biodegradation of polyclorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs)

The objective of this minireview is to examine how cometabolic biodegradation of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) might be affected by plant terpenes and lignins as natural substrates abundant in nature. The topics covered, hence, are environmental significance of PCBs and PAHs, nature and distribution of plant terpenes and lignin, structural and metaoblic similarities of the natural compounds to PCBs and PAHs, and possible roles of the natural substrates in inducing the biodegradative pathways of PCBs and PAHs.     

The influence of polychlorinated biphenyls (PCBs) and phytoestrogens in vitro on functioning of reproductive tract in cow

Ovarian, endometrial and myometrial cells and strips of longitudinal myometrium from cows on defined days of estrous cycle were treated for 24-72 h with different doses (1-100 ng/ml) of PCBs mixture (Aroclor 1248) or with one of PCB congeners (126, 77, 153). The administered doses of PCBs neither affected the viability of cells nor influenced the ovarian steroidogenesis as measured by progesterone (P(4)), estradiol (E(2)) and testosterone secretion from luteal, granulosa and theca cells, respectively. In contrast, PCBs clearly inhibited a FSH and LH-stimulated effect on steroids secretion from granulosa and luteal cells. Moreover, PCBs significantly stimulated oxytocin (OT) secretion from the studied ovarian cells, and at least part of this effect is elicited through activation of glucocorticoid receptors. Further, PCBs were found to increase basal intracellular concentrations of Ca(2+) and both spontaneous and OT-stimulated contractions of myometrial strips. Concomitantly, PCBs increased endometrial secretion of PGF(2alpha), hence the ratio of PGF(2alpha):PGE(2) was also increased. Phytoestrogens (genistein, daidzein, coumestrol), with a different intensity, reduced the effect of PCBs on PGF(2alpha) secretion and myometrial contractions. Genistein inhibited PCBs' effect on OT secretion from granulosa cells, while PCB's effect on OT release from luteal cells was reduced mainly by genistein and daidzein. We conclude that PCBs can impair both ovarian functioning and uterine contractility, while phytoestrogens are able to reduce this effect.     

An Insight into the Active Site of Pseudomonas Fluorecens (P. cepacia) Lipase to Define the Stereochemical Demand for the Transesterification in Organic Solvents

The Pseudomonas fluorescens lipase-catalyzed transesterification of 2-methyl alkanols 1 and the 2-substituted oxiranemethanols 2 with vinyl acetate in organic solvents has been studied and the results discussed in terms of steric and electronic demand within the recently postulated models of the lipase active site.     

In vitro effects of polychlorinated biphenyls (PCBs) on the contractility of bovine myometrium from the periovulatory stage of the estrous cycle

Strips of longitudinal myometrium from cows were obtained on days 19-21 and 1-5 of the estrous cycle and incubated (aerated atmosphere; 4 degrees C; 24, 48 or 72 h) with a mixture of PCBs Aroclor (Ar) 1248 or with one of three PCBs (77, 126 or 153), all at doses of 10 or 100 ng/ml. The force and frequency of spontaneous and oxytocin (OT; 10(-7)M)-stimulated contractions of each strip was registered by means of HSE Schuler Organbath. Contractions of myometrial strips in the presence and absence of PCBs were observed after 24, 48 and 72 h of incubation. All PCBs significantly affected myometrial contractions. A mixture of PCBs increased the spontaneous force of contractions after 24 h but decreased after 48 h. Individual congeners of PCB also amplified the force of contractions and in most cases this effect was dose-dependent. Response of myometrium to PCB-126 and PCB-153 or PCB-77 appeared after 24 h or 48 h of incubation. Incubation of myometrial strips with PCB congeners markedly amplified OT-stimulated contractions. This effect was less evident when tissue was pre-treated with a higher dose of PCBs. Pre-treatment with estrogen-like PCB-153 increased the spontaneous and OT-evoked frequency of myometrial contractions from days 19-21. The spontaneous force of myometrial strips' contractions as well as the effects evoked by PCBs and OT was higher before than after ovulation. In summary, PCBs affected both the force and frequency of uterine contractions. Thus, it can be concluded that PCBs may impair both ovum fertilization and blastocyst implantation in cows.     

The influence of increasing chlorine content on the accumulation and metabolism of polychlorinated biphenyls (PCBs) by Paul's Scarlet Rose cells

Four radiolabled congeners of biphenyls with increasing chlorine content (biphenyl; 1-monochlorobiphenyl; 2,2,4,4-tetrachlorobiphenyl; and 2,2,4,4,5,5-hexachlorobiphenyl) were provided to suspension cultures of rose (Rosa sp. cv. Paul's Scarlet) for 4 days. Both the kinetics of ¹⁴C exchange between the cells and medium, and the metabolism of the parent compounds depended on the chlorine content of the congeners. Analysis of both the cells and their medium showed that of the recovered radioactivity 88%, 86%, and 3% of the biphenyl, 1-PCB, and 2,2,4,4-PCB were metabolized respectively to polar and insoluble residue products. The 2,2,4,4,5,5-PCB did not appear to be metabolized.