Effect of high zinc concentrations on the growth of Stichococcus bacillaris and Chlorella vulgaris

The effect of concentrations of zinc from 50 to 400 mg/l on the growth of Stichococcus bacillaris and Chlorella vulgaris under laboratory conditions was examined. The growth of both species was inhibited in proportion to the concentration of the metal in the medium. S. bacillaris was more tolerant to high zinc concentrations than C. vulgaris. Microscopical examination of cells growing in medium with zinc did not reveal any significant changes compared to the control cultures.     

Cadmium removal by living cells of the marine microalga Tetraselmis suecica

Cadmium removal by living cells of the marine microalga Tetraselmis suecica was tested in cultures exposed to different cadmium concentrations (0.6, 3, 6, 15, 30 and 45 mg/l). The EC50 for growth was 7.9 mg Cd/l after six days of exposure. The cadmium removed was proportional to the concentration of this metal in the medium and it was dependent on the time of exposure; cultures with higher cadmium concentration removed a higher amount of this metal. In cultures exposed to 0.6 mg/l, T suecica cells removed 98.1% of added cadmium with 0.392 x 10(-6) microg Cd/cell, whereas in cultures with 45 mg/l only 7.7% was removed with 16.052 x 10(-6) microg Cd/cell. The highest amount of cadmium removed per liter of culture was observed in cultures exposed to 6 mg/l, with 3.577 mg/l of cadmium. After six days of incubation, the higher proportion of cadmium was bioaccumulated intracellularly in all cultures except in 45 mg/l cultures, the percentage of intracellular cadmium being always more than 50%. The highest percentage of bioadsorbed cadmium (60.1%) was found in cells of cultures with the highest cadmium concentration (45 mg/l). Furthermore, a relation between intracellular cadmium and the concentration of sulfhydryl groups was observed.     

Studies on the purification of wastewater from the nitrogen fertilizer industry by intensive algal cultures. I. Growth of Chlorella vulgaris in wastes.

The possibility of growth of intensive cultures of Chlorella vulgaris on industrial wastewater from nitrogen fertizer plant containing ammonia, urea and nitrate was investigated. Good growth of algae was obtained when the waste was enriched with phosphorus and inoculum contained a high number of cells. The optimal pH for the culture was 7.0--8.0. The main factor limiting growth of algae on wastes on the concentration of ammonia nitrogen. Chlorella vulgaris grows quite well in wastes containing 600 mg NH4-N/l but is inhibited at concentration about 100 mg NH4-N/l.     

Intraspecific variability in growth response to cadmium of the wood-rotting fungus Piptoporus betulinus

The intraspecific variability in growth response to cadmium (Cd) on agar media and in liquid culture was studied among fourteen strains of a wood-rotting fungus Piptoporus betulinus. The variability of Cd tolerance was found to be very high. The ED(50) ranged from 6.8 μM Cd in the most sensitive strain, up to 255.1 μM in the most resistant one. On agar media the addition of Cd to nutrient media resulted in reduction of relative growth rate and increased lag time. While the reduction of growth rate was already apparent at 10 μM Cd, the lag time was significantly increased in higher Cd concentrations. Five strains of P. betulinus failed to grow at 250 μM Cd and none grew at 500 μM metal. Biomass production in liquid culture was less sensitive to addition of Cd than the growth rate on solid media. At 100 μM Cd the radial growth rate of the mycelium was reduced to 27%, whereas the dry mass of mycelium was 77% of the respective control value. A group of four Cd-sensitive strains was found, showing low metal tolerance both on solid media and in liquid cultures. Although the isolates originated from sites with different Cd-pollution level, no correlation between level of Cd-pollution and resistance (ED(50)) was found. The growth rate of fourteen tested strains displayed lower variability than biomass production, showing that radial growth rate is more species-specific and therefore more valuable for interspecific comparisons of growth response.     

Effects of arsenate (AS5+) on growth and production of glutathione (GSH) and phytochelatins (PCS) in Chlorella vulgaris

The effect of arsenate (As5+) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated. C. vulgaris was tolerant to As5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent, indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5 mg/L in media containing 200 mg/L As5+ suggesting that GSH plays a more prominent role in the detoxification of As5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As5+ detoxification, whereas above this concentration As5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defense mechanisms, such as increased production of GSH. The overall findings complement field studies which suggest C. vulgaris as an increasingly promising low cost As phytoremediation method for developing countries.     

Poly(γ-glutamylcysteinyl)glycines or phytochelatins and their role in cadmium tolerance of Silene vulgaris

Abstract. The effect of cadmium on growth of Cd-tolerant and -sensitive plants of Silene vulgaris and on the production of metal-binding compounds in both types of plants was studied. The Cd-content of the roots and the Cd-root/shoot ratio was higher in Cd-tolerant plants. A Cd-binding compound (Cd-BC) with an apparent molecular mass of 14.5 kD was isolated from the roots of Cd-tolerant and -sensitive plants, grown in 40 mmol m⁻³ Cd for 21 d. More than 60% of the total Cd in the roots was associated with this compound. Determination of the amino-acid content of the purified Cd-containing compound from both types of plants showed that they possessed a similar amino-acid composition to that of phytochelatins. Only the bis- and tris-forms were present. The amount of Cd and sulphide associated with phytochelatin was greater in tolerant plants than in sensitive ones suggesting that an increased sulphide content of complexes containing peptide, sulphide and Cd may form the basis of evolved Cd-tolerance in Silence vulgaris.     

Accumulation of cadmium by channel catfish (Ictalurus punctatus): influx from environmental solutions.

1. The accumulation of cadmium (Cd) from external environmental solutions was measured in channel catfish (Ictalurus punctatus) with the aid of 109Cd and by direct analysis of tissues. 2. Acute uptake (with 109Cd) was concentration dependent and was increased by changing the external pH from 7.3 to 5.0 and decreased by raising the Ca concentration from 0.1 mM to 3.0 mM. 3. The presence of external Zn did not change the uptake of the Cd. 4. In chronic 7-day experiments, fasted catfish were found to accumulate the toxic metal in their liver and kidneys from external media with Cd concentrations as low as 10(-9) M (about 0.1 microgram/l). 5. Concentrations were greater in the kidneys than the liver. 6. Detectable amounts of Cd (less than 0.03 microgram/g net wt) were not found in muscle in this time at external concentrations of Cd less than 10(-5) M (less than 1.0 mg/l).     

Heterotrophic bacteria accompanying Stichococcus bacillaris in laboratory cultures

The number and composition of bacterial microflora accompanying Stichococcus bacillaris in various media with urea was determined. The number of heterotrophic bacteria during 5 days of incubation increased 10-fold. Only some of the isolated bacterial strains were able to grow in medium for algae supplemented with dead S. bacillaris cells. It is suggested that bacteria utilize organic matter released to the medium by S. bacillaris. The most numerous among the isolated bacteria were Enterobacteriaceae. The order of domination by bacterial populations distinguishes nonaxenic cultures of S. bacillaris from cultures of other algae.     

四种抗寒花卉对镉的生理响应和富集特征

以矮型四季菊、羽扇豆、欧报春和虞美人等冬春季常见花卉为试验材料,通过盆栽试验,研究了不同浓度Cd处理下4种花卉对Cd的生理响应和富集特征,探讨利用这4种花卉在冬春季寒冷时期修复Cd污染土壤的可行性,为提高植物修复技术的效率提供参考。结果表明:(1)在所有Cd处理下,羽扇豆各部位生物量与对照均无差异;欧报春仅根系生物量在80 mg·kg^-1Cd处理时显著低于对照,为对照的74.51%;矮型四季菊和虞美人全株生物量分别在Cd处理浓度高于10、40 mg·kg^-1时开始显著低于对照,并在80 mg·kg^-1Cd处理时全株生物量均达到最小值,分别为对照的41.21%和64.15%。(2)在所有Cd处理下,羽扇豆体内抗氧化酶活性均显著高于对照,MDA含量与对照无显著性差异,清除活性氧能力最强,未受到伤害;欧报春体内抗氧化酶活性升高幅度较小,MDA含量和REC有小幅度增加,清除活性氧的能力较强,受到的伤害程度较低;矮型四季菊和虞美人对活性氧清除能力最差,受到了严重的氧化伤害。(3)在所有Cd处理下,Cd在矮型四季菊体内的分布均为地上部>根系,BCF和TF均大于1,地上部含量和富集量最大值分别为136.20mg·kg^-1和1118.20μg·plant^-1;Cd在羽扇豆、欧报春、虞美人体内表现为地上部<根系,TF均小于1,地上部Cd含量、富集量、BCF和TF均为羽扇豆>欧报春、虞美人。综上所述,与欧报春和虞美人相比,矮型四季菊对Cd耐性相对较差,但对Cd有较强的吸收转移能力,适合用于冬春季Cd污染土壤的修复;羽扇豆对Cd的耐性强,对Cd吸收转移能力也较强,也适合用于冬春季Cd污染土壤的修复。     

Characteristics of cadmium accumulation and tolerance in novel Cd-accumulating crops, Avena strigosa and Crotalaria juncea

Characteristics of accumulation and tolerance of cadmium (Cd) in green manure crops were investigated to identify Cd-accumulating crops and to clarify the mechanisms involved in Cd accumulation and tolerance. Seedlings of eight crop species were treated with Cd (1 mg l(-1) or 5 mg l(-1)) in the growing medium for 4 d. Cd concentration in leaves of Avena strigosa Schreb. cv. New-oat, Crotalaria juncea L. and Tagetes erecta L. cv. African-tall was greater than values used to define Cd-hyperaccumulation (>100 mg Cd kg(-1) DW). However, in leaves of T. erecta, lipid peroxidation level increased significantly, and the activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and catalase were depressed by both Cd treatments. By contrast, A. strigosa and C. juncea exhibited high Cd tolerance. Avena strigosa leaves showed higher activities of antioxidative enzymes such as superoxide dismutase and ascorbate peroxidase than those of other species tested. Crotalaria juncea showed higher amounts of total soluble phenolics which, in leaves, were doubled by 5 mg l(-1) Cd treatment. When two Cd-tolerant accumulators (A. strigosa and C. juncea) and the non-accumulator (C. spectabilis) were treated with lower Cd concentrations for 4 weeks, A. strigosa and C. juncea exhibited superior Cd accumulation in the shoots with greater biomass production compared with C. spectabilis. These results indicate that A. strigosa and C. juncea possess the greater potential for Cd accumulation and tolerance than common crops.     

A comparison of dressed crab and a cadmium salt (CdCl2) as cadmium sources in rat diets

1. A long term low level exposure experiment was conducted on rats in order to determine the metabolic patterns of realistic environmental dietary levels of cadmium from different sources. 2. Male and female rats were fed a diet for 6 months with a high crab content containing 4 mg Cd/kg as organic bound cadmium from dressed crab, a diet with low crab content containing 0.2 mg Cd/kg as organic bound cadmium, a casein based diet containing 4 mg Cd/kg as cadmium chloride and a low cadmium level control diet. 3. Analysis of the cadmium levels in the kidney, liver and spleen showed that uptake from the dressed crab was only half of that from the diet fortified with cadmium chloride.     

Improvement of clavulanic acid production by Streptomyces clavuligerus in medium containing soybean derivatives

The effect of the nitrogen source in the production medium on the level of clavulanic acid production by Streptomyces clavuligerus has been investigated. Batch cultures using two types of synthetic culture medium and two types of complex culture medium containing soybean derivatives were employed. To allow comparison of the various media, all of them were formulated with 4.0 g total nitrogen/l. It was observed that the production of clavulanic acid using synthetic medium reached values slightly greater than those usually found in the literature. However, in trials with complex media, it was found that when Samprosoy 90NB (protein extract of soybean) was utilized, production of clavulanic acid went up to 920 mg/l, twice as high as when soy meal was used, and notably higher than values reported in the literature (300–500 mg/l) for complex medium.     

Cadmium accumulation in tissues of the mussel Mytilus galloprovincialis

Studies have been made on cadmium accumulation in tissues of mussels kept within 20-60 days in water artificially enriched by Cd up to 20-100 micrograms/l. Irrespectively of cadmium concentration in the medium, its accumulation in tissues decreases in the following order: mid-gut gland, gills, gonads, mantle, adductor. Maximum concentration of Cd was found in the digestive tubuli of the mid-gut gland by X-ray microanalysis. The increase in S and, to a lower extent, P concentrations in these tubuli was also observed. It is suggested that the latter is due to immobilization of Cd by metal-binding proteins as well as to lyzosomal vesicles involved into detoxication of Cd. The increase in the external cadmium up to 100 micrograms/l did not affect the level of K, Ca and Mg in tissues of the mussel.     

Effects of Cd2+ and two cadmium organic complexes on isolated rat liver mitochondria

Effects of Cd2+ and two complexes of bivalent cadmium with 1,3-bis(4-chlorbenzylidenamino)-guanidine and anabasine on ion permeability of the inner membrane and respiration of isolated rat liver mitochondria were studied. Starting from 5 microM, Cd2+ decreased state 3 and DNP-stimulated respiration of mitochondria and increased their state 4 respiration. At 30 microM, Cd2+ decreased state 4 respiration. The complexes, particularly complex of Cd2+ with 1,3-bis(4-chlorbenzylidenamino)-guanidine, inhibited the mitochondrial respiration at lower concentration of Cd2+. Nonenergized mitochondria incubated in media containing 125 mM of NH4NO3 or KNO3 showed more pronounced swelling in experiments with 10 microM of the complexes than with Cd2+. The complexes produced swelling of the mitochondria energized by 5 mM of succinate and incubated in medium containing 25 mM K-acetate and 100 mM sucrose. Uptake of 137-Cs by succinate-energized mitochondria in the presence of 10(-8) M of valinomycin was substantially decreased in experiments with 10 microM of the complexes than with Cd2+. Ruthenium red (7.5 microM) prevented this effect with 10 microM of complex of Cd2+ with 1,3-bis(4-chlorbenzylidenamino)-guanidine and especially complex of Cd2+ with anabasine and Cd2+. These results indicate that the cadmium organic complexes affect respiration and perturb ion permeability significantly stronger than Cd2+.     

The Effect of High-Concentration Auxin and Plant Regeneration in the Immature Embryo Culture of Soybean

Using immature embryos of soybean as explants, green structures and somatic embryoids were able to be induced on higher auxin-containing media. Genotypes, developmental degree of the embryos, origin of the explants and medium compositions all affected the occurrence of the structures and calli. After the green structures were transferred to high 2,4-D containing medium (30 mg/l) calli were reinduced. These calli were maintained on the same medium without being subcultured for 2 months and then transferred to lower hormone-containing media. After 2 weeks, a great number of new green structures in the same shapes were induced. It was shown that high level of 2,4-D played a unique role in lasting the morphogenesis ability of the cultures. When the green structure were cultured on low hormone-containing media they developed new leaves and formed leaf clusters while the apical did not develop. In order to stimulate the apical development the medium containing 2 mg/l GA3 and 0.1 mg/l IBA was used and some plantlets were obtained. The different effects of NAA and 2,4-D on the explants and calli were studied. Calli induced from the cotyledon of immature seeds (416 mm) had a regeneration ability stronger than that from the seedlings. The calli induced by use of the medium containing high concentration of 2,4-D (5–30 mg/l) have higher potentialities in producing green structures. In contrast, the calli induced by high concentration of NAA (10 mg/l) were highly root-morphogenetic. The explants and the calli cultured on the medium containing 5 mg/l 2,4-D could be maintained for a long term without being subcultured frequently.     

Screening of marine microalgae for bioremediation of cadmium-polluted seawater

Twenty four strains out of 191 marine microalgal strains exhibited cadmium (Cd) resistance. They were tested for their Cd removal ability in growth media containing 50 μM Cd. Six strains out of 19 green algae and one out of five cyanobacteria removed more than 10% of total Cd from the medium. The marine green alga Chlorella sp. NKG16014 showed the highest removal of Cd 48.7% of total. Cd removal by NKG16014 was further quantitatively evaluated by measuring the amount of cell adsorption and intracellular accumulation. After 12 days incubation, 67% of the removed Cd was accumulated intracellularly and 25% of the Cd removed was adsorbed on the algal cell surface. The maximum Cd adsorption (q_max) was estimated to be 37.0 mg Cd (g dry cells)⁻¹ using the Langmuir sorption model. The Cd removal by freeze-dried NKG16014 cells was also determined. Cd was more quickly adsorbed by dried cells than that by living cells, with a q_max of 91.0 mg Cd (g dry cells)⁻¹.     

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.     

Sublethal maternal pre-exposure of fish to cadmium. Effect on the survival of the newly hatched alevins

The aim of this study was to determine the effects of the exposure of pregnant females of a viviparous teleost Cnesterodon decemmaculatus to sublethal Cd solutions on the survival of their offspring. Ovigerous females were acclimated and accomodated in aquaria containing the following solutions: artificial freshwater medium (AFW) and AFW with 25, 50 and 100 microg Cd(2+) /L (as chloride). Part of the offspring born from control females was transferred to media contain-ing 25, 50 and 100 microg/L of cadmium; the rest of the fry stayed in AFW solutions without cadmium. The offspring born from the females maintained in solutions of cadmium were transferred to aquaria with AFW, and to solutions containing metal at the same concentration as their mother. In all cases mortality was recorded daily for 168 h. The results demonstrated that the survival of newborn offspring was always related to the concentration of Cd(2+) to which they were exposed at birth, regardless of the concentration of the metal to which the mother was exposed during its pregnancy. When exposed to Cd(2+), alevins from non-exposed females showed a constant linear death rate while in those from Cd-exposed it resulted exponential.     

Cadmium biosorption by Saccharomyces cerevisiae

Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. (c) 1993 Wiley & Sons, Inc.     

Anaerobic digestion of cattail with rumen culture in the presence of heavy metals

The anaerobic digestion of cattail by rumen cultures in the presence of Cu(II), Cd(II) or Cr(VI) was investigated in this study. Three cases were respectively observed for the different metal dosages: promoted cattail degradation and methane production at a low heavy metal concentration, e.g., Cu(II) 2.4 mg/l, Cd(II) 1.6 mg/l, Cr(VI) 4.0 mg/l; reduced cattail degradation efficiency and methane production at a middle metal level; a severe inhibition to the cattail degradation at a high heavy metal dosage. The inhibition kinetics of Cu(II) on the digestion of cattail by rumen cultures was also analyzed and a simplified Andrews equation was used to describe such an inhibition. The inhibition constants for Cu(II) on the degradation of cattail, production of volatile fatty acids and formation of methane were estimated as 7.4, 9.5 and 6.4 mg/l, respectively. Comparative experimental results suggest that the order of toxicity degree of the tested metals on the rumen cultures was: Cd(II) > Cu(II) > Cr(VI).