Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.

Experiments in semi-natural conditions were undertaken to assess hemp metal tolerance and its ability to accumulate cadmium, nickel and chromium. Cannabis sativa was grown in two soils, S1 and S2, containing 27, 74, 126 and 82, 115, 139 g g^–1 of Cd, Ni and Cr, respectively. After two months from germination and at ripeness, no significant alteration in plant growth or morphology was detected. On the contrary, a high hemp reactivity to heavy metal stress with an increase in phytochelatin and DNA content was observed during development, suggesting the Cannabis sativa ability to avoid cell damage by activating different molecular mechanisms. Metals were preferentially accumulated in the roots and only partially translocated to the above-ground tissues. The mean shoot Cd content was 14 and 66 g g^–1 for S1 and S2 soil, respectively. Although not negligible concentrations they were about 100 times lower than those calculated for the hyperaccumulator Thlaspi caerulescens. Similarly Ni uptake was limited if compared with that of the Ni-hyperaccumulator Alyssum murale. Chromium uptake was negligible. As expected on the base of the metal concentration detected in ripe plants, no statistically significant variation in soil metal content was detected after one crop of hemp. Nevertheless, a consistent amount (g) of Cd and Ni is expected to be extracted by 1 ha biomass of hemp (about 10 t) per year and along the time a slow restoration of deeper soil portions can be obtained by its wide root system (at least 0,5 m deep). In addition, the possibilities of growing hemp easily in different climates and using its biomass in non-food industries can make heavy metal contaminated soils productive. This means economical advantage along with a better quality of soil.     

Effects of organic amendments on Cd, Zn and Cu bioavailability in soil with repeated phytoremediation by Sedum plumbizincicola

Organic materials with different functional groups can be used to enhance metal bioavailability. Traditional organic materials (rice straw and clover) and ethylenediamine disuccinic acid (EDDS) were applied to enhance metal uptake from polluted soil by Sedum plumbizincicola after repeated phytoextraction. Changes in pH, dissolved organic carbon (DOC) and metal concentrations were determined in the soil solution after EDDS application. Amendment of the soil with ground rice straw or ground clove resulted in higher concentrations of Cd only (by factors of 1.92 and 1.71 respectively) in S. plumbizincicola compared to control soil. Treatment with 3 mmol kg(-1) EDDS increased all the metals studied by factors of 60.4, 1.67, and 0.27 for Cu, Cd, and Zn, respectively. EDDS significantly increased soil solution DOC and pH and increased soil plant-available metals above the amounts that the plants could take up, resulting in high soil concentrations of soluble metals and high risk of ground water contamination. After repeated phytoremediation of metal contaminated soils the efficiency of metal removal declines as the concentrations of bioavailable metal fractions decline. Traditional organic materials can therefore be much more effective and environmentally friendly amendments than EDDS in enhancing phytoremediation efficiency of Cd contaminated soil     

Food choice of Antarctic soil arthropods clarified by stable isotope signatures

Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common and widely distributed Antarctic soil arthropod species using natural abundances of ¹³C and ¹⁵N and an isotope labelling study. In the laboratory we fed the isotomid springtail Cryptopygus antarcticus six potential food sources (one algal species, two lichens and three mosses). Our results showed a clear preference for algae and lichens rather than mosses. These results were corroborated by field data comparing stable isotope signatures from the most dominant cryptogams and soil arthropods (C. antarcticus and the oribatid mite Alaskozetes antarcticus). Thus, for the first time in an Antarctic study, we present clear evidence that these soil arthropods show selectivity in their choice of food and have a preference for algae and lichens above mosses.     

Heavy metal uptake by arbuscular mycorrhizas of Elsholtzia splendens and the potential for phytoremediation of contaminated soil

A pot culture experiment and a field experiment were carried out separately to study heavy metal (HM) uptake from soil contaminated with Cu, Zn, Pb and Cd by Elsholtzia splendens Nakai ex F. Maekawa inoculated with arbuscular mycorrhizal (AM) fungi and the potential for phytoremediation. The HM-contaminated soil in the pot experiment was collected from the field experiment site. Two AM fungal inocula, MI containing only one AM fungal strain, Glomus caledonium 90036, and M II consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp. andGlomus spp., were applied to the soil under unsterilized conditions. In the pot experiment, the plants were harvested after 24 weeks of growth. Mycorrhizal colonization rate, plant dry weight (DW) and P, Cu, Zn, Pb, Cd concentrations were determined. MI-treated plants had higher mycorrhizal colonization rates than MII-treated plants. Both MI and MII increased shoot and root DW, and MII was more effective than MI. In shoots, the highest P, Cu, Zn and Pb concentrations were all observed in the plants treated with MII, while MI decreased Zn and Pb concentrations and increased P but did not alter Cu, and Cd concentrations were not affected by either of two inocula. In roots, MII increased P, Zn, Pb concentrations but did not alter Cu and Cd, and MI did not affect P, Cu, Zn, Pb, Cd concentrations. Cu, Zn, Pb, Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants, Cu and Zn uptake into shoots and Cu, Zn, Pb, Cd into roots increased but Pb and Cd uptake into shoots decreased. In general, MII was more effective than MI in promoting plant growth and HM uptake. The field experiment following the pot experiment was carried out to investigate the effects of MII under field conditions. The 45-day-old nonmycorrhizal and MII-colonized seedlings of E. splendens were transplanted to HM-contaminated plots and harvested after 5 months. MII-inoculation increased shoot DW and shoot P, Cu, Zn, Pb concentrations significantly but did not alter shoot Cd concentrations, which led to higher uptake of Cu, Zn, Pb, Cd by E. splendens shoots. These results indicate that the AM fungal consortium represented by MII can benefit phytoextraction of HMs and therefore play a role in phytoremediation of HM-contaminated soils.     

Intrapopulation variation in carbon and nitrogen stable isotope ratios in the earthworm Aporrectodea longa

The natural abundance variations in carbon and nitrogen stable isotope ratios in a population of the earthworm Aporrectodea longa, a species known to feed on both soil and plant litter, is reported in this paper. Worms were collected from a small land area of an old white clover field and body tissue and mucus were analyzed separately. The range of isotopic values was small, but patterns of variation were not random. Tissue carbon and nitrogen isotope ratios were significantly higher in adult than in juvenile A. longa and tissue nitrogen isotope ratios tended to increase with increasing biomass of individuals. Further, carbon and nitrogen isotope ratios were positively correlated in both tissue and mucus. Possible causes of the observed patterns, including physiological effects, body composition and assimilation of C and N from different plant, soil and microbial sources are discussed. It is concluded that the causes of natural variability in isotopic composition must be understood and validated experimentally before natural abundance stable isotope methods can be used for the analysis of trophic relations among detritivorous soil invertebrates.     

Quantification of the mycotoxins patulin and ochratoxin A by stable isotope dilution assays

For analysis of trace compounds, stable isotope dilution assays (SIDAs) have gained increasing importance in the past years. This methodology is based on the use of stable isotopically labelled analogues of the analytes as internal standards (IS). To take the mycotoxins patulin and ochratoxin A as examples, the benefits of SIDAs were demonstrated both for foods and for clinical analyses. Regarding PAT, an isotopomer labelled with¹³C was used as IS and enabled quantitation of the mycotoxin in tissues and blood. By applying this technology, a fast passive diffusion into tissue was proven with the model of the perfused rat stomach. Furthermore, rapid degradation of PAT was observed when it was reacted with blood, which was attributed to the formation of PAT-GSH adducts detected by LC-MS/MS. For OTA, a SIDA was based on the use of [²H₅]-OTA as the IS and proved to be more accurate when compared to alternative methods such as HPLC-FD or ELISA. In contrast to PAT, OTA was detectable in human blood and urine samples. Under the assumption that the majority of OTA is circulating in blood, an urinary excretion rate of about 1% of the whole body content per day was calculated. Presented at the 27^th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005 Financial support: in part by a grant from the Deutsche Forschungsgemeinschaft (Ry, 19/4-1)     

The effect of plant growth-promoting rhizobacteria on the phytoextraction of Cd and Zn by Brassica napus L.

The test strains Bacteroidetes bacterium (Ba), Pseudomonas fluorescens (Pf) and Variovorax sp. (Va) were selected in advance for their in vitro capability for growth promotion of rapeseed in the presence of increased concentrations of Cd, Cu, Pb and Zn in the medium. In the pot experiment, the strains were used for single Ba, Pf, Va or combined Ba + Pf, Ba + Va, Pf + Va, and Ba + Pf + Va inoculation of B. napus growing in contaminated soil from alluvial deposits. The positive effect of bacterial strains on plant growth was observed in vitro, but was not confirmed in situ in the contaminated soil, where the tested strains inhibited biomass production, rather than stimulating it. However, single inoculation with Ba significantly increased the chlorophyll content and K⁺ concentration in the leaves. The inoculation of rapeseed with Ba and Va strains was indicated to be the most promising combination for phytoextraction of Cd and Zn from contaminated soil. Combined inoculation with Pf+Va and Pf + Ba+Va significantly decreased the concentration of heavy metals in the roots of rapeseed. We conclude that suitable combinations of PGPR can control the metal uptake of B. napus, selectively increasing either metal extraction or metal stabilization in the rhizosphere and offering promising applications in soil remediation.     

Assessment of Zn mobilization in the rhizosphere of Thlaspi caerulescens by bioassay with non-accumulator plants and soil extraction

This study used co-cultivated plants as a bioassay to test the hypothesis that the roots of the zinc-hyperaccumulating plant Thlaspi caerulescensmobilize Zn from less-available pools in the soil. Thlaspi caerulescens was grown in uncompartmentalised pots, or pots that were divided by solid or mesh barriers to limit the extent of root intermingling (rhizosphere interaction) with co-cultivated Thlaspi arvense or Festuca rubra. Thlaspi caerulescens did not increase the concentration of Zn in either indicator species, suggesting that T. caerulescens does not strongly mobilize Zn in its rhizosphere. The increase in the shoot mass of T. arvense when its roots were permitted to intermingle with those of T. caerulescens was explained by greater intensity of competition of T. arvense compared to T. caerulescens.There was no effect of co-cultivation with T. caerulescens on the shoot biomass of F. rubra. Despite the absence of increased Zn-availability to the co-cultivated species, the mass of Zn accumulated by T. caerulescens was 3-times greater than the mass of Zn depleted from the pool of extractable-Zn in the soil, measured by extraction with 1 M ammonium nitrate. The results are consistent with the hypothesis that the rapid Zn-uptake systems in the roots of T. caerulescens deplete the soluble-Zn at a rate equal to, or faster than that at which Zn is replenished to the soil solution via plant/microbially mediated mobilization or the Zn-buffering capacity of the soil.     

典型海湾与海岛近海脉红螺碳、氮稳定同位素特征差异

为深入了解不同大小脉红螺(Rapana venosa)的碳、氮稳定同位素特征,探究其在典型海湾和海岛水域生态系统所处营养位置,于2022年春季和夏季在胶州湾和长岛近海通过拖网和潜水采集160个脉红螺样本,详细分析了不同体长、体重脉红螺的δ¹³C和δ¹⁵N变化,并计算各研究区域的脉红螺核心生态位宽度及相关参数。结果显示,脉红螺δ¹³C值范围在-22.12‰--16.63‰,四组数据均值为-19.74‰--17.42‰,δ¹⁵N值范围在8.77‰-13.48‰,均值为9.64‰-12.81‰,各组数据营养级均值在2.63-3.57;胶州湾春季脉红螺δ¹³C值与体长、体重呈显著负相关,夏季呈显著正相关,长岛近海区域无明显变化,表明不同季节和不同区域的食物多样性水平存在差异, 胶州湾脉红螺δ¹³C、δ¹⁵N的变化更为突出;两个研究区域δ¹⁵N值和营养级与体长、体重呈显著正相关,主要由于脉红螺摄食偏好性差异,较大的脉红螺倾向于摄食高营养级生物,造成营养级较高。此外,胶州湾脉红螺营养级高于长岛近海,表明其¹⁵N来源更为广泛。营养生态位总面积、δ¹⁵N差值、δ¹³C差值、校正后标准椭圆面积等评价指标,揭示了不同区域、不同季节的脉红螺稳定同位素营养生态位的显著差异,反映了区域地理位置与食物来源对脉红螺δ¹³C和δ¹⁵N的影响。上述研究结果为近海生态系统食物网的构建提供了重要数据,并为区域生物资源的管理和生态系统修复工作提供了科学支撑。     

Nutrient routing in omnivorous animals tracked by stable carbon isotopes in tissue and exhaled breath

Omnivorous animals feed on several food items that often differ in macronutrient and isotopic composition. Macronutrients can be used for either metabolism or body tissue synthesis and, therefore, stable C isotope ratios of exhaled breath (delta(13)C(breath)) and tissue may differ. To study nutrient routing in omnivorous animals, we measured delta(13)C(breath) in 20-g Carollia perspicillata that either ate an isotopically homogeneous carbohydrate diet or an isotopically heterogeneous protein-carbohydrate mixture. The delta(13)C(breath) converged to the delta(13)C of the ingested carbohydrates irrespective of whether proteins had been added or not. On average, delta(13)C(breath) was depleted in (13)C by only ca. -2 per thousand in relation to the delta(13)C of the dietary carbohydrates and was enriched by +8.2 per thousand in relation to the dietary proteins, suggesting that C. perspicillata may have routed most ingested proteins to body synthesis and not to metabolism. We next compared the delta(13)C(breath) with that of wing tissue (delta(13)C(tissue)) in 12 free-ranging, mostly omnivorous phyllostomid bat species. We predicted that species with a more insect biased diet--as indicated by the N isotope ratio in wing membrane tissue (delta(15)N(tissue))--should have higher delta(13)C(tissue) than delta(13)C(breath) values, since we expected body tissue to stem mostly from insect proteins and exhaled CO(2) to stem from the combustion of fruit carbohydrates. Accordingly, delta(13)C(tissue) and delta(13)C(breath) should be more similar in species that feed predominantly on plant products. The species-specific differences between delta(13)C(tissue) and delta(13)C(breath) increased with increasing delta(15)N(tissue), i.e. species with a plant-dominated diet had similar delta(13)C(tissue) and delta(13)C(breath) values, whereas species feeding at a higher trophic level had higher delta(13)C(tissue) than delta(13)C(breath) values. Our study shows that delta(13)C(breath) reflect the isotope ratio of ingested carbohydrates, whereas delta(13)C of body tissue reflect the isotope ratio of ingested proteins, namely insects, supporting the idea of isotopic routing in omnivorous animals.     

荒漠植物梭梭稳定碳同位素组成与环境因子的关系

以广泛分布于新疆荒漠地区的建群种植物——梭梭(Haloxylon ammodendron)为研究对象,通过对23个样地101份梭梭同化枝样品δ~(13)C值的测定,分析了梭梭稳定碳同位素组成的变化特征及其与环境因子(海拔、日照时数、潜在蒸散量、年平均降水量和年平均温度)的关系,并讨论了不同生境下梭梭同化枝δ~(13)C值的变化特征。研究结果显示:(1)梭梭同化枝δ~(13)C平均值为-14.15‰,其在95%置信区间的变化范围为-13.14‰—-15.38‰,表明梭梭是C_4光合途径的植物。(2)梭梭同化枝δ~(13)C值与年平均降水量和年平均温度呈显著负相关关系,而与日照时数、潜在蒸散量和海拔呈显著正相关关系。我们推测梭梭同化枝δ~(13)C值对各环境因子响应趋势的不同,可能是由气孔限制因素造成的,它是梭梭适应干旱荒漠环境的一种策略。(3)在不同生境下,梭梭同化枝的碳同位素组成存在显著差异。当梭梭群落中的主要伴生种为白刺、红砂时,其δ~(13)C值最高,当主要伴生种为沙拐枣和假木贼时,其δ~(13)C值最低。在灰漠土与灰棕漠土样地中的梭梭δ~(13)C值高于棕钙土、风沙土、石质土样地;盆地中梭梭同化枝δ~(13)C值低于平原、山地、丘陵地形条件下的样地。以上结果表明:梭梭水分利用效率在不同环境梯度和生境中,存在着显著不同,表现出显著的适应策略差异。     

基于碳、氮稳定同位素的厦门筼筜湖两种优势端足类食性分析

测定了厦门市筼筜湖(内、外湖)大型海藻群落两种优势端足类(强壮藻钩虾Ampitheoe valida和上野蜾蠃蜚Corophium uenoi)及其潜在食源的碳、氮稳定同位素比值(δ~(13)C和δ~(15)N),分析研究了这两种端足类摄食习性的空间变动特征。研究发现,端足类的潜在食源包括悬浮颗粒有机物(Particulate organic matter:POM),沉积有机物(Sedimentary organic matter:SOM),石莼(Ulva lactuca:Ulva)及其表面的附生生物(Epiphytes:Epi),它们的δ~(13)C和δ~(15)N值分别介于-24.0‰(POM)—-11.8‰(Ulva)和-1.7‰(POM)—4.7‰(Ulva)之间。其中,Ulva和POM的δ~(13)C值的内、外湖差异不显著;而外湖SOM和Epi的δ~(13)C值则明显高于内湖。采样区SOM有机质来源的空间差异是其δ~(13)C内、外湖差异的主要原因。除POM外,外湖有机碳源的δ~(15)N明显高于内湖,这与它们利用氮源的δ~(15)N的差异有关。潜在食源稳定同位素组成的空间差异,使得筼筜湖端足类的稳定同位素组成,尤其是δ~(15)N值表现出显著的空间变动特征(强壮藻钩虾和上野蜾蠃蜚δ~(15)N的内、外湖差异高达1.6‰和4.2‰,变幅约1个营养级),但2种端足类食性的空间差异却不尽相同:强壮藻钩虾的食性相对稳定,其δ~(13)C值介于Ulva和Epi之间,表明它主要从Ulva及其表面的Epi获取碳源;而上野蜾蠃蜚的食性内、外湖差异较大:内湖从石莼表面的Epi获取碳源,约20%是来自POM的贡献,而外湖则主要以Ulva及其表面的Epi为食。分析显示,筼筜湖内、外湖端足类δ~(15)N的空间差异并不是端足类的营养级发生了变化,而是由于端足类食源δ~(15)N的空间差异引起的,而不同端足类食性的内、外湖差异则可能与环境中饵料的丰度和生物量密切相关。     

浙江南部近海前肛鳗营养生态位变化研究——基于稳定同位素技术

基于2016年和2020年浙江南部近海收集的71尾前肛鳗样品,通过测定碳氮稳定同位素比值计算其营养生态位指标,对比分析前肛鳗不同发育过程、不同季节及不同年份营养生态位的差异,探究营养生态位的变动规律及对资源的利用情况。结果表明：(1)2016年和2020年前肛鳗平均δ¹³C值分别为(-15.19±0.31)‰、(-15.90±0.45)‰;平均δ¹⁵N值分别为(12.42±0.45)‰、(12.92±0.25)‰;(2)单因素方差分析表明,2016年前肛鳗不同发育过程δ¹³C值差异不显著(P>0.05),δ¹⁵N值差异显著(P<0.05),不同季节间δ¹³C值和δ¹⁵N值均存在显著差异(P<0.05),而2020年前肛鳗不同发育过程δ¹³C值和δ¹⁵N值差异均不显著(P>0.05),不同季节间δ¹³C值存在显著差异(P<0.05),δ¹⁵N...     

The use of stable sulfur isotope labelling to elucidate sulfur metabolism by Clostridium pasteurianum

An unique stable isotope labelling experiment was conducted whereby mixtures of sulfate and sulfite of different isotopic compositions were metabolized by Clostridium pasteurianum. The results showed during reduction of 1 mM SO ₃ ⁼ plus 1 mM SO ₄ ⁼ , essentially all evolved H₂S arose from the sulfite whereas in the case of cellular sulfur, 85% was derived from sulfite and the remainder from sulfate.     

The role of root-associatedKlebsiella pneumoniae in the nitrogen nutrition ofPoa pratensis andTriticum aestivum as estimated by the method of15N isotope dilution

Summary The technique of¹⁵N isotope dilution was used to verify that nitrogen was fixed and transferred to the plant byKlebsiella pneumoniae strain Pp in association withPoa pratensis orTriticum aestivum. Surface sterilized, sprouting seeds were inoculated withK. pneumoniae and grown in sand in modified Leonard jars. Potassium nitrate enriched with¹⁵N was used to provide N concentrations ranging from 10–40 mg Nl^–1 nutrient solution. After 10–18 weeks the shoots and roots were analyzed separately for dry matter, N content, total N, and atom %¹⁵N excess. The acetylene reduction technique was used to test for the presence of N₂-fixing organisms on the roots. The data from¹⁵N isotope dilution demonstrated that up to 33.8% of N in the shoots ofP. pratensis and 15.9% in those ofT. aestivum were derived from associative N₂ fixation byK. pneumoniae. In most experiments the dry matter yield, N content, and total N yield of the shoots ofP. pratensis were increased byK. pneumoniae inoculation, whereas inoculation had no significant effect on the dry matter yield, N content or total N of the shoots ofT. aestivum.     

纳塔栎和柳叶栎对铅锌矿区污染土壤的修复潜力分析:田间试验

通过野外调查、采样和实验室分析方法,研究优新景观树种纳塔栎（Quercus nuttallii）和柳叶栎（Quercus phellos）对湖南郴州Pb、Zn矿区复合污染土壤的适应性和修复潜力。试验设计A、B、E区种植1年生纳塔栎,C、D区种植1年生柳叶栎,1年后测量株高、地径、生物量等生长指标,随机采集植物全株及根际土壤,测试植物根际土壤和树木组织中的重金属含量。试验结果：Pb、Zn矿区土壤受到重金属Cd、Pb、Zn和As的复合污染,不同区域的土壤表现出污染异质性,采用单污染指数（Pi）和内梅罗指数（P_N）评价不同地块的污染程度,A区尾矿库（P_N=20.08）和B区（P_N=3.14）为重度复合污染,C区（P_N=2.43）为中度复合污染,D区（P_N=1.55）和E区（P_N=1.07）为轻微污染。纳塔栎和柳叶栎在以上不同污染地块均能正常生长,株高、地径和生物量与复合污染指数（内梅罗指数）及重金属含量呈负相关。其中纳塔栎对Cd的生物富集系数（BCF）在A、B、E区分别为6.27-8.37、3.67-4.38、42.93-52.75,高于C、D区柳叶栎对Cd的生物富集系数1.79-2.15、0.89-1.07。B-E区Zn的转运系数（TF）在1.79-2.28之间,A区Zn的转运系数为0.43。结论：纳塔栎和柳叶栎表现出较强的重金属耐性,对Cd具有较高的生物富集能力,对Zn具有较高的转运能力。其中纳塔栎对重金属积累能力较强,可作为亚热带地区铅锌矿区Cd、Pb、Zn、As复合污染土壤的植被恢复及生态修复候选树种。     

Analysis of modified bases in DNA by stable isotope dilution gas chromatography-mass spectrometry: 5-Methylcytosine

A sensitive assay for 5-methylcytosine in DNA has been developed based on stable isotope dilution gas chromatography-mass spectrometry with selected ion monitoring. 5-([²H₃]-Methyl)cytosine and [methyl-²H₃]thymine have been synthesized as internal standards for analysis of DNA following acid digestion, conversion of pyrimidines to volatile t-butyldimethylsilyl derivatives, and separation in 3 min by gas chromatography. Submicrogram amounts of DNA have been analyzed for 5-methylcytosine content in the range 0.02–1.5 mol%. The estimated limit of quantitative measurement is 0.3 pmol of methylated base in a DNA hydrolysate. The method is compared with other techniques for quantitative measurement of methylated bases in DNA, and 5-methylcytosine levels and precision of analysis for calf thymus, pBR322, and ΦX-174 DNAs are reported and compared with literature values. The method can readily be adapted to the accurate high-sensitivity analysis of other methylated bases in DNA.     

Microalgae as a source of stable isotopically labeled compounds

Microalgae have the ability to convert inorganic compounds into organic compounds. When they are cultured in the presence of stable (non-radioactive) isotopes (i.e.¹³CO₂,¹⁵NO ₃ ^– ,²H₂O) their biomass becomes labeled with the stable isotopes, and a variety of stable isotopically-labeled compounds can be extracted and purified from that biomass.Two applications for stable isotopically-labeled compounds are as cell culture nutrients and as breath test diagnostics. Bacteria that are cultured with labeled nutrients will produce bacterial products that are labeled with stable isotopes. The presence of these isotopes in the bacterial products, along with recent developments in NMR technology, greatly reduces the time and effort required to determine the three-dimensional structure of macromolecules and the interaction of proteins with ligands. As breath test diagnostics, compounds labeled with¹³C are used to measure the metabolism of particular organs and thus diagnose various disease conditions. These tests are based on the principle that a particular compound is metabolized primarily by a single organ, and when that compound is labeled with¹³C, the appearance of¹³CO₂ in exhaled breath provides information about the metabolic activity of the target organ. Tests of this type are simple to perform, non-invasive, and less expensive than many conventional diagnostic procedures.The commercialization of stable isotopically labeled compounds requires that these compounds be produced in a cost-effective manner. Our approach is to identify microalgal overproducers of the desired compounds, maximize the product content of those organisms, and purify the resulting products.     

Interspecific differences in Zn,Cd and Pb accumulation by freshwater algae and bryophytes

The relationships between the concentrations of zinc, cadmium and lead in aquatic plants and the concentrations of these metals in the ambient water have been compared for three algae (Lemanea fluviatilis, Cladophora glomerata, Stigeoclonium tenue), one liverwort (Scapania undulata) and three mosses (Amblystegium riparium, Fontinalis antipyretica, Rhynchostegium riparioides). The data to establish these relationships are all based on our own studies, some published already, some here for the first time. They come from a wide range of streams and rivers in Belgium, France, Germany, Ireland, Italy and the U.K. There were significant bivariate positive relationships between concentrations of Zn, Cd and Pb in water and plant for all species except Cd and Pb in Stigeoclonium tenue. When relationships were compared using datasets with total or filtrable metals in water, most differences were slight. However there were marked differences both between species and between metals. Comparison for the seven species of Zn in the plant when aqueous Zn is 0.01 mg l^–1, a concentration at which all seven were found, shows that the four bryophytes had the highest concentrations; however the two green algae had steeper slopes (representing change in concentration in plant in response to change in aqueous concentration). Lemanea fluviatilis had a slope closer to that of the bryophytes, but the concentration was about one order of magnitude lower. All seven species were found at a concentration of 0.01 mg l^–1 Pb, and at this concentration there were almost two orders of magnitude difference between the species which accumulated the most (Scapania undulata) and the one which accumulated the least (Cladophora glomerata). The steepest slope was however shown by C. glomerata.When multiple stepwise regression was applied, the aqueous metal under consideration was the first variable extracted in only nine of the 21 regressions. However one of the other heavy metals (aqueous or accumulated) was extracted first in all but one of the other regressions, presumably because the occurrences of Zn, Cd and Pb were strongly cross-correlated. The principal non-heavy metal factor extracted for Zn and Cd, but not Pb, was aqueous Ca. The relevance of these results to the use of aquatic plants for monitoring heavy metals is discussed.