An investigation into the ability of soft drinks to adhere to enamel

A mixed culture, isolated from soil contaminated with polycyclic aromatic hydrocarbons (PAHs), grew on and degraded fluoranthene in aqueous media supplemented with glucose, yeast extract, and peptone. Increased complex nitrogen levels in the medium promoted bacterial growth and a greater extent of fluoranthene degradation. Amendment of the media with high glucose levels also diminished specific fluoranthene degradation. The mixed culture was capable of degrading a range of other PAHs, including benzo[a]pyrene, anthracene, phenanthrene, acenaphthene, and fluorene. The mixed culture contained four predominant isolates, all of which were Gram-negative rods, three of which were identified as Pseudomonas putida, Flavobacterium sp., and Pseudomonas aeruginosa. Better degradation of a defined PAH mixture was observed with the mixed culture than with individual isolates. A reconstituted culture, prepared by combining the four individual isolates, manifested a similar PAH biodegradation performance to the original mixed culture. When compared with the mixed culture, individual isolates exhibited a relatively good capacity to remove more water-soluble PAHs (acenaphthene, fluorene, phenanthrene, fluoranthene). In contrast, removal of less water-soluble PAHs (anthracene and pyrene) was low or negligible with isolated cultures compared with the mixed culture.     

Religiosity as a protective or prognostic factor of depression in later life; results from a community survey in The Netherlands

OBJECTIVES: This study explored the possibility of using urinary 1-naphthol excretion as a marker of complex exposure among workers handling creosote. METHODS: Urine specimens of 6 workers from a creosote impregnation plant, where railroad ties were impreganted with coal tar creosote, were collected during 1 workweek, and the concentration of 1-naphthol was determined. 1-Naphthol in spot urine samples of 5 occupationally nonexposed male smokers was used as the background reference. Concurrently, naphthalene and 10 different polycyclic aromatic hydrocarbons (PAH) were determined in personal air samples. RESULTS: The mean airborne exposure of the workers was 1.5 mg/m3 for vaporous naphthalene, 5.9 micrograms/m3 for particulate PAH and 1.4 micrograms/m3 for PAH with 4-6 aromatic rings. The mean urinary concentration of 1-naphthol at the end of the workshift was 20.5 (range 3.5-62.1) mumol/l, whereas the referents' urinary concentration was below the detection limit (0.07 mumol/l). Airborne naphthalene correlated fairly well with 1-naphthol when measured at the end of the shift (r = 0.745). CONCLUSIONS: This method of analysis for 1-naphthol is sufficiently sensitive for measuring low occupational exposures to naphthalene. Low background exposures are, however, unlikely to result in detectable urinary levels of 1-naphthol. Since naphthalene is the most abundant compound in creosote vapor, urinary 1-naphthol determination serves well as a biological marker of exposure to vaporous creosote. Urinary 1-naphthol alone is not, however, a suitable marker for inhalatory or cutaneous exposure to PAH originating from creosote.     

Enhancement of Aromatic Hydrocarbon Biodegradation by Toluene and Naphthalene Degrading Bacteria Obtained from Lake Sediment: The Effects of Cosubstrates and Cocultures

Toluene and naphthalene degrading (ND) bacteria, obtained from contaminated lake sediment, were used to degrade both monoaromatics and polycyclic aromatic hydrocarbons (PAHs) and the effects of cosubstrates and cocultures were examined. When toluene and naphthalene enrichments were used, the effect of the substrate interaction on their metabolism was found to be inhibitory and yet the cocultures were stimulatory, especially for toluene enrichment degradation of naphthalene (with toluene). Pseudomonas putida M2T14, a toluene degrading isolate, could efficiently degrade benzene and toluene but not naphthalene. Nonetheless, when toluene was present, this monoaromatic degrader became capable of degrading PAHs, among which the methyl substituted PAHs (mPAHs) were preferred to their corresponding unsubstituted PAHs (uPAHs). Pseudomonas azelaica ND isolate could degrade benzene, toluene, and all test PAHs. Although the uPAHs were preferred, the degradation rates of mPAHs were greatly increased via substrate interactions with naphthalene. The interaction modes of dual aromatic hydrocarbons (AHs) degraded by P. putida M2T14 and P. azelaica ND were cometabolism, synergism, no effect, inhibition, and antagonism. However, when a negative effect of biodegradation from the interaction of these AHs was found on one isolate, a positive effect would be found on the other. When benzene was present, it exhibited inhibitory effects on aromatic hydrocarbon biodegradation by M2T14 and ND isolates. A study of the biodegradation of the ternary mixture of benzene, toluene, and naphthalene by both isolates together illustrated that not only was inhibition relieved but that degradation of each compound was also greatly enhanced. Degradation by the toluene and the ND bacteria could be facilitated by complementary substrate interactions between monoaromatics and PAHs and by bacterial association. These model organisms may be very useful for the study of complex aromatic hydrocarbon degradation and for bioremediation purposes.     

Use of 13C nuclear magnetic resonance and gas chromatography to examine methionine catabolism by lactococci

Formation of methanethiol from methionine is widely believed to play a significant role in development of cheddar cheese flavor. However, the catabolism of methionine by cheese-related microorganisms has not been well characterized. Two independent methionine catabolic pathways are believed to be present in lactococci, one initiated by a lyase and the other initiated by an aminotransferase. To differentiate between these two pathways and to determine the possible distribution between the pathways, 13C nuclear magnetic resonance (NMR) performed with uniformly enriched [13C]methionine was utilized. The catabolism of methionine by whole cells and cell extracts of five strains of Lactococcus lactis was examined. Only the aminotransferase-initiated pathway was observed. The intermediate and major end products were determined to be 4-methylthio-2-oxobutyric acid and 2-hydroxyl-4-methylthiobutyric acid, respectively. Production of methanethiol was not observed in any of the 13C NMR studies. Gas chromatography was utilized to determine if the products of methionine catabolism in the aminotransferase pathway were precursors of methanethiol. The results suggest that the direct precursor of methanethiol is 4-methylthiol-2-oxobutyric acid. These results support the conclusion that an aminotransferase initiates the catabolism of methionine to methanethiol in lactococci.     

Species-specific oligonucleotides for enumeration of Pseudomonas putida F1, Burkholderia sp. strain JS150, and Bacillus subtilis ATCC 7003 in biodegradation experiments

Species-specific sequences were identified within the V4 variable region of 16S rRNA of two bacterial species capable of aromatic hydrocarbon metabolism, Pseudomonas putida F1 and Burkholderia sp. strain JS150, and a third, Bacillus subtilis ATCC 7003, that can function as a secondary degrader. Fluorescent in situ hybridization (FISH) with species-specific oligonucleotides was used for direct counting of these species throughout a phenol biodegradation experiment in batch culture. Traditional differential plate counting methods could not be used due to the similar metabolism and interactions of the primary degraders and difficulties in selecting secondary degraders in mixed culture. In contrast, the FISH method provided reliable quantitative results without interference from those factors.     

13C-NMR spectroscopic evaluation of the citric acid cycle flux in conditions of high aspartate transaminase activity in glucose-perfused rat hearts

A new mathematical model, based on the observation of 13C-NMR spectra of two principal metabolites (glutamate and aspartate), was constructed to determine the citric acid cycle flux in the case of high aspartate transaminase activity leading to the formation of large amounts of labeled aspartate and glutamate. In this model, the labeling of glutamate and aspartate carbons by chemical and isotopic exchange with the citric acid cycle are considered to be interdependent. With [U-13C]Glc or [1,2-(13)C]acetate as a substrate, all glutamate and aspartate carbons can be labeled. The isotopic transformations of 32 glutamate isotopomers into 16 aspartate isotopomers or vice versa were studied using matrix operations; the results were compiled in two matrices. We showed how the flux constants of the citric acid cycle and the 13C-enrichment of acetyl-CoA can be deduced from 13C-NMR spectra of glutamate and/or aspartate. The citric acid cycle flux in beating Wistar rat hearts, aerobically perfused with [U-13C]glucose in the absence of insulin, was investigated by 13C-NMR spectroscopy. Surprisingly, aspartate instead of glutamate was found to be the most abundantly-labeled metabolite, indicating that aspartate transaminase (which catalyses the reversible reaction: (glutamate + oxaloacetate <--> 2-oxoglutarate + aspartate) is highly active in the absence of insulin. The amount of aspartate was about two times larger than glutamate. The quantities of glutamate (G0) or aspartate (A0) were approximately the same for all hearts and remained constant during perfusion: G0 = (0.74 +/- 0.03) micromol/g; A0 = (1.49 +/- 0.05) micromol/g. The flux constants, i.e., the fraction of glutamate and aspartate in exchange with the citric acid cycle, were about 1.45 min(-1) and 0.72 min(-1), respectively; the flux of this cycle is about (1.07 +/- 0.02) micromol min(-1) g(-1). Excellent agreement between the computed and experimental data was obtained, showing that: i) in the absence of insulin, only 41% of acetyl-CoA is formed from glucose while the rest is derived from endogenous substrates; and ii) the exchange between aspartate and oxaloacetate or between glutamate and 2-oxoglutarate is fast in comparison with the biological transformation of intermediate compounds by the citric acid cycle.     

空气氧化苊制备1,8—萘酐的研究

开发出一种以苊为原料合成１，８－萘酐的高效催化剂，试验表明使用该催化剂催化空气氧化苊制备１，８－萘酐产率达１１１％，纯度达９８％。     

Portacaval anastomosis results in altered neuron--astrocytic metabolic trafficking of amino acids: evidence from 13C-NMR studies

13C-NMR spectroscopy was used to evaluate the dynamic consequences of portacaval anastomosis on neuronal and astrocytic metabolism and metabolic trafficking between neurons and astrocytes. Glutamate is predominantly labeled from [1-13C]glucose, whereas [2-13C]acetate is more efficient in labeling glutamine, in accordance with its primary metabolism in astrocytes. Alanine and succinate labeling was only observed with [1-13C]glucose as precursor. Brain [1-13C]glucose metabolism in portacaval-shunted rats was similar to that in sham-operated controls with the exception of labeled glutamine and succinate formation, which was increased in shunted rats. The 13C enrichment was, however, decreased owing to an increase in total glutamine and succinate. Using [2-13C]acetate, on the other hand, flux of astrocytic label to neurons was severely decreased because label incorporation into glutamate, aspartate, and GABA was decreased following portacaval shunting. The latter amino acids are predominantly localized in neurons. These findings demonstrate that metabolic trafficking of amino acids from astrocytes to neurons is impaired in portacaval-shunted rats.     

Biodegradation of Naphthalene-Contaminated Soils in Slurry Bioreactors

The effects of naphthalene concentrations and soil constituents (sand, clay, organic matter) on biodegrading naphthalene-contaminated soils using an acclimated Flavobacterium sp. were examined in continuously stirred slurry bioreactors. Soils with and without organic matter (1%) and kaolinite clay (20%) were used. Studies showed that sorption of naphthalene can be represented by the Freundlich isotherm. Among the soils investigated, clayey soil retarded the biodegradation process the most due to its desorption characteristics. Increasing the naphthalene contamination level from 500 mg∕kg to 25,000 mg∕kg doubled the biodegradation time in the slurry reactor with a soil loading of 10 g∕L. A pseudo first-order kinetic was observed for naphthalene biodegradation, and the biodegradation constant was determined to be 0.20 mg∕L∕h. A kinetic model was developed to simulate the biodegradation of naphthalene in a continuously stirred batch slurry reactor and to understand the role of solubilization (solid phase naphthalene), desorption, and biodegradation in the removal of naphthalene. Predictions using the numerical model agreed with the experimental data.     

Biocatalysis, biodegradation and bioinformatics

Biocatalysis, biodegradation and bioinformatics are prominent scientific fields in industrial microbiology and biotechnology. This paper describes developments in these fields with a focus on the role of David T Gibson as a researcher and mentor. He has pioneered studies on the mechanisms by which aerobic microorganisms transform aromatic hydrocarbons. In addition, his research has served as a model for further investigations into bacterial atrazine and dichloromethane catabolism described here. Microbial catabolism research requires information on organic chemistry, microorganisms, metabolic pathways, catabolic genes, and enzymes. These information needs are now being met more comprehensively by development of the University of Minnesota Biocatalysis/Biodegradation Database.     

In vitro and ex vivo 13C-NMR spectroscopy studies of pyruvate recycling in brain

Pyruvate recycling is a well established pathway in the liver, but in the brain, the cellular localization of pyruvate recycling remains controversial and its physiological significance is unknown. In cultured cortical astrocytes, pyruvate formed from [U-13C]glutamate was shown to re-enter the TCA cycle after conversion to acetyl-CoA, as demonstrated by the labelling patterns in aspartate C-2 and C-3, lactate C-2, and glutamate C-4, which provides evidence for pyruvate recycling in astrocytes. This finding is in agreement with previous studies of astrocytic cultures, in which pyruvate recycling has been described from [U-13C]glutamine, in the presence of glutamate, and from [U-13C]aspartate. Pyruvate recycling in brain was studied in fasted rats receiving either an intraperitoneal or a subcutaneous injection of [1,2-13C]acetate followed by decapitation 30 min later. Extracts of cortical tissue were analysed with 13C-NMR spectroscopy and total amounts of amino acids quantified by HPLC. Plasma extracts were analysed with 1H- and 13C-NMR spectroscopy, and showed a significantly larger amount of [1, 2-13C]acetate in the intraperitoneal group compared to the subcutaneous group. Furthermore, a small amount of label was detected in glucose in both groups. In the subcutaneously injected rats, [4-13C]glutamate and [2-13C]GABA were less enriched than plasma glucose, which might have been the precursor. In the intraperitoneally injected rats, however, pyruvate formation from [1, 2-13C]acetate, and re-entry of this pyruvate into the TCA cycle was demonstrated by the presence of greater 13C enrichment in [4-13C]glutamate and [4-13C]glutamine compared to the subcutaneous group, probably resulting from the significantly higher [1, 2-13C]acetate concentration in brain and plasma.     

Cerebral metabolic compartmentation as revealed by nuclear magnetic resonance analysis of D-[1-13C]glucose metabolism

Nuclear magnetic resonance (NMR) was used to study the metabolic pathways involved in the conversion of glucose to glutamate, gamma-aminobutyrate (GABA), glutamine, and aspartate. D-[1-13C]Glucose was administered to rats intraperitoneally, and 6, 15, 30, or 45 min later the rats were killed and extracts from the forebrain were prepared for 13C-NMR analysis and amino acid analysis. The absolute amount of 13C present within each carbonatom pool was determined for C-2, C-3, and C-4 of glutamate, glutamine, and GABA, for C-2 and C-3 of aspartate, and for C-3 of lactate. The natural abundance 13C present in extracts from control rats was also determined for each of these compounds and for N-acetylaspartate and taurine. The pattern of labeling within glutamate and GABA indicates that these amino acids were synthesized primarily within compartments in which glucose was metabolized to pyruvate, followed by decarboxylation to acetyl-CoA for entry into the tricarboxylic acid cycle. In contrast, the labeling pattern for glutamine and aspartate indicates that appreciable amounts of these amino acids were synthesized within a compartment in which glucose was metabolized to pyruvate, followed by carboxylation to oxaloacetate. These results are consistent with the concept that pyruvate carboxylase and glutamine synthetase are glia-specific enzymes, and that this partially accounts for the unusual metabolic compartmentation in CNS tissues. The results of our study also support the concept that there are several pools of glutamate, with different metabolic turnover rates.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ability of 16 priority PAHs to be directly cytotoxic to a cell line from the rainbow trout gill

Sixteen polycyclic aromatic hydrocarbons (PAHs) were screened for their ability to be directly cytotoxic to a cell line from the rainbow trout gill, RTgill-W1. Exposure times of 2 h or less were sufficient for direct cytotoxicity to be detected, which appeared to be caused by a common mechanism, the general perturbation of membranes. This was judged by the similarity of results obtained for three fluorescent indicator dyes, alamar Blue, 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM) and neutral red. Among the 16 PAHs tested, just two- and three-ring PAHs were found to be directly cytotoxic. These were naphthalene approximately = acenaphthylene approximately = acenaphthene > fluorene approximately = phenanthrene. The results suggest that water solubility and lipophilicity are the critical properties determining the direct cytotoxicity of PAHs and that they do so by influencing PAH accumulation in membranes. Only naphthalene was effective at concentrations well below its water solubility limit. Therefore, direct cytotoxicity is likely to be most environmentally relevant only with naphthalene.     

2,4-Dinitrotoluene dioxygenase from Burkholderia sp. strain DNT: similarity to naphthalene dioxygenase

2,4-Dinitrotoluene (DNT) dioxygenase from Burkholderia sp. strain DNT catalyzes the initial oxidation of DNT to form 4-methyl-5-nitrocatechol (MNC) and nitrite. The displacement of the aromatic nitro group by dioxygenases has only recently been described, and nothing is known about the evolutionary origin of the enzyme systems that catalyze these reactions. We have shown previously that the gene encoding DNT dioxygenase is localized on a degradative plasmid within a 6.8-kb NsiI DNA fragment (W.-C. Suen and J. C. Spain, J. Bacteriol. 175:1831-1837, 1993). We describe here the sequence analysis and the substrate range of the enzyme system encoded by this fragment. Five open reading frames were identified, four of which have a high degree of similarity (59 to 78% identity) to the components of naphthalene dioxygenase (NDO) from Pseudomonas strains. The conserved amino acid residues within NDO that are involved in cofactor binding were also identified in the gene encoding DNT dioxygenase. An Escherichia coli clone that expressed DNT dioxygenase converted DNT to MNC and also converted naphthalene to (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene. In contrast, the E. coli clone that expressed NDO did not oxidize DNT. Furthermore, the enzyme systems exhibit similar broad substrate specificities and can oxidize such compounds as indole, indan, indene, phenetole, and acenaphthene. These results suggest that DNT dioxygenase and the NDO enzyme system share a common ancestor.     

钢铁厂油泥堆场PAHs的污染特性研究

以某钢厂油泥堆放场的油泥为研究对象,油泥样品按照多环芳烃(PAHs)来源的不同分为石油源油泥样品和混合源油泥样品,通过高效液相色谱法对样品中PAHs进行测定.结果显示,油泥样品中PAHs主要来自于石油源.萘、苊烯、苊、芴和菲是油泥中PAHs的主要污染物.油泥样品中16种优控PAHs的总含量(∑PAHs)为0.973～1...     

Comparison of Mixed Cultures Based on Activity

Biodegradation experiments using mixed bacterial cultures are difficult to compare because repeatable rates may not be produced in different experiments when cultures are normalized on a cell mass or number basis. A technique was therefore developed to quantify [14C]substrate-specific biodegradation activity of mixed cultures. The technique can be used to obtain a preliminary estimate of the substrate-degrading activity of a culture for more substantial experiments. The technique is applied to 1-naphthol-humic acid bioavailability experiments using both mixed and pure cultures to help isolate the impact of humic acid from differences between the cultures.     

The evidence of clonal evolution with monosomy 7 in aplastic anemia following granulocyte colony-stimulating factor using the polymerase chain reaction

The polycyclic aromatic hydrocarbons (PAH) containing fractions of smoked and charcoal-broiled foods, namely, Sheat fish (Kytopterus apogon), Mimrow (Crossocheilus reba), Freshwater catfish (Clarias batrachus), chicken wings, rice pork sausage and pork, in addition to naphthalene, acenaphthene, anthracene, phenanthrene, fluoranthene, pyrene, benz[a]anthracene, naphthacene, benzo[a]pyrene, benzo[e]pyrene, 9,10-dimethyl-1,2-benzanthracene, dibenz[ah]anthracene, benzo[ghi]perylene and coronene, were evaluated for their mutagenic potential using Salmonella typhimurium strains TA98 and TA100 in the absence of metabolic activation after being treated with nitrite (500 mM) for 4 hr at 37 degrees C and in acid solution pH 3.0-3.5. The presence of N-nitroso compounds was also determined. Results showed that nitrite could convert most samples to direct-acting mutagens towards both strains except for fluoranthene and benzo[ghi]perylene, which exhibit mutagenicity only with TA98. It was demonstrated that treatment of PAHs with nitrite in acid solution produced some non-N-nitroso direct-acting mutagens, suggesting that they might belong to nitro-PAHs. Therefore, the consumption of charcoal-broiled and smoked foods simultaneously with nitrite is not recommended.     

Effect of polycyclic aromatic hydrocarbons on the elimination kinetics of pyrene and the urinary excretion profile of 1-hydroxypyrene in the rat

Pyrene was chosen as a noncarcinogen model of polycyclic aromatic hydrocarbons (PAHs). Groups of male Wistar rats were dosed with pyrene and with mixture of pyrene and fluoranthene, pyrene and benz[a]anthracene, or pyrene, fluoranthene, and benz[a]anthracene at 20 mg/kg by intravenous or oral routes. Blood samples were taken at 0.25, 0.5, 1, 2, 3, 4, and 5 h after administration. The concentration of pyrene was determined by gas chromatography. The toxicokinetic parameters for pyrene were determined from the time course of blood concentration. A significant increase in the bioavailability of pyrene after treatment with other PAHs was observed. Urinary 1-hydroxypyrene excretion was analyzed after pretreatment with acenaphthene, naphthalene, chrysene, phenanthrene, benz[a]anthracene, and benzo[a]pyrene. The urine from rats was collected for 3 d and the concentration of 1-hydroxypyrene was determined using high-performance liquid chromatography (HPLC). Most compounds examined caused a decrease in the urinary excretion of the metabolite of pyrene.     

焦化废水中苯胺和萘等物质在厌氧条件下去除规律的研究

在实验室保证厌氧条件下,通过恒温摇床试验,研究焦化废水中芳烃类物质苯胺、萘和茚的降解去除规律,同时对这三种芳烃类有机物在水相和泥相中的含量进行了测定。研究结果表明：苯胺的厌氧去除主要通过生物降解,但微生物需要一个适应过程;萘和茚的厌氧去除途径是吸附在污泥上进行降解,茶经过48h可降解完全,茚的吸附属物理吸附,是可逆的。     

In vivo injection of [1-13C]glucose and [1,2-13C]acetate combined with ex vivo 13C nuclear magnetic resonance spectroscopy: a novel approach to the study of middle cerebral artery occlusion in the rat

Astrocytes play a pivotal role in cerebral glutamate homeostasis. After 90 minutes of middle cerebral artery occlusion in the rat, the changes induced in neuronal and astrocytic metabolism and in the neuronal-astrocytic interactions were studied by combining in vivo injection of [1-13C]glucose and [1,2-13C]acetate with ex vivo 13C nuclear magnetic resonance spectroscopy and HPLC analysis of amino acids of the lateral caudoputamen and lower parietal cortex, representing the putative ischemic core, and the upper frontoparietal cortex, corresponding to the putative penumbra. In the putative ischemic core, evidence of compromised de novo glutamate synthesis located specifically in the glutamatergic neurons was detected, and a larger proportion of glutamate was derived from astrocytic glutamine. In the same region, pyruvate carboxylase activity, representing the anaplerotic pathway in the brain and exclusively located in astrocytes, was abolished. However, astrocytic glutamate uptake and conversion to glutamine took place, and cycling of intermediates in the astrocytic tricarboxylic acid cycle was elevated. In the putative penumbra, glutamate synthesis was improved compared with the ischemic core, the difference appeared to be brought on by better neuronal de novo glutamate synthesis, combined with normal levels of glutamate formed from astrocytic glutamine. In both ischemic regions, gamma-aminobutyric acid synthesis directly from glucose was reduced to about half, indicating impaired pyruvate dehydrogenase activity; still, gamma-aminobutyric acid reuptake and cycling was increased. The results obtained in the current study demonstrate that by combining in vivo injection of [1-13C]glucose and [1,2-13C]acetate with ex vivo 13C nuclear magnetic resonance spectroscopy, specific metabolic alterations in small regions within the rat brain suffering a focal ischemic lesion can be studied.