Phenylpropanoid pathway in plants and its role in response to heavy metal stress: a review / 生物工程学报

Phenylpropanoid metabolic pathway is one of the most important secondary metabolic pathways in plants. It directly or indirectly plays an antioxidant role in plant resistance to heavy metal stress, and can improve the absorption and stress tolerance of plants to heavy metal ions. In this paper, the core reactions and key enzymes of the phenylpropanoid metabolic pathway were summarized, and the biosynthetic processes of key metabolites such as lignin, flavonoids and proanthocyanidins and relevant mechanisms were analyzed. Based on this, the mechanisms of key products of phenylpropanoid metabolic pathway in response to heavy metal stress were discussed. The perspectives on the involvement of phenylpropanoid metabolism in plant defense against heavy metal stress provides a theoretical basis for improving the phytoremediation efficiency of heavy metal polluted environment.

Sagittaria sagittifolia polysaccharides regulates Nrf2/HO-1 to relieve liver injury caused by multiple heavy metals in vivo and in vitro / 中国中药杂志

This study explored whether Sagittaria sagittifolia polysaccharides(SSP) activates the nuclear factor erythroid-2-related factor2(Nrf2)/heme oxygenase-1(HO-1) signaling pathway to protect against liver damage jointly induced by multiple heavy metals. First, based on the proportion of dietary intake of six heavy metals in rice available in Beijing market, a heavy metal mixture was prepared for inducing mouse liver injury and HepG2 cell injury. Forty male Kunming mice were divided into five groups: control group, model group, glutathione positive control group, and low-and high-dose SSP groups, with eight mice in each group. After 30 days of intragastric administration, the liver injury in mice was observed by HE staining. In the in vitro experiment, MTT assay was conducted to detect the effects of SSP at 0.25, 0.5, 1, and 2 mg·mL~(-1) on HepG2 cell survival at different time points. The content of alanine transaminase(ALT) and aspartate aminotransferase(AST) in the 48-h cell culture fluid was measured using micro-plate cultivation method, followed by the detection of the change in reactive oxygen species(ROS) content by flow cytometry. The mRNA expression levels of Nrf2 and HO-1 in cells were determined by RT-PCR, and their protein expression by Western blot. HE staining results showed that compared with the model group, the SSP administration groups exhibited significantly alleviated inflammatory cell infiltration and fatty infiltration in the liver, with better outcomes observed in the high-dose SSP group. In the in vitro MTT assay, compared with the model group, SSP at four concentrations all significantly increased the cell survival rate, decreased the ALT, AST, and ROS content(P<0.05), and down-regulated Nrf2 and HO-1 mRNA and protein expression(P<0.05). SSP significantly improves inflammatory infiltration in the liver tissue of mice exposed to a variety of heavy metals and corrects the liver fat degeneration, which may be related to its regulation of the Nrf2/HO-1 signaling pathway, reduction of ROS, and alleviation of oxidative damage.

Bioremediation of heavy metals in food industry: application of Saccharomyces cerevisiae

Heavy metals are natural elements in the Earth's crust that can enter human food through industrial or agricultural processing, in the form of fertilizers and pesticides. These elements are not biodegradable. Some heavy metals are known as pollutants and are toxic, and their bioaccumulation in plant and animal tissues can cause undesirable effects for humans; therefore, their amount in water and food should always be under control. The aim of this study is to investigate the conditions for the bioremediation of heavy metals in foods. Various physical, chemical, and biological methods have been used to reduce the heavy metal content in the environment. During the last decades, bioremediation methods using plants and microorganisms have created interest to researchers for their advantages such as being more specific and environmentally friendly. The main pollutant elements in foods and beverages are lead, cadmium, arsenic, and mercury, which have their own permissible limits. Among the microorganisms that are capable of bioremediation of heavy metals, Saccharomyces cerevisiae is an interesting choice for its special characteristics and being safe for humans, which make it quite common and useful in the food industry. Its mass production as the byproduct of the fermentation industry and the low cost of culture media are the other advantages. The ability of this yeast to remove an individual separated element has also been widely investigated. In countries with high heavy metal pollution in wheat, the use of S. cerevisiae is a native solution for overcoming the problem of solution. This article summarizes the main conditions for heavy metal absorption by S. cerevisiae.

Heavy metal tolerance traits of filamentous fungi isolated from gold and gemstone mining sites

ABSTRACT Increased environmental pollution has necessitated the need for eco-friendly clean-up strategies. Filamentous fungal species from gold and gemstone mine site soils were isolated, identified and assessed for their tolerance to varied heavy metal concentrations of cadmium (Cd), copper (Cu), lead (Pb), arsenic (As) and iron (Fe). The identities of the fungal strains were determined based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Mycelia growth of the fungal strains were subjected to a range of (0-100 Cd), (0-1000 Cu), (0-400 Pb), (0-500 As) and (0-800 Fe) concentrations (mgkg-1) incorporated into malt extract agar (MEA) in triplicates. Fungal radial growths were recorded every three days over a 13-days' incubation period. Fungal strains were identified as Fomitopsis meliae, Trichoderma ghanense and Rhizopus microsporus. All test fungal exhibited tolerance to Cu, Pb, and Fe at all test concentrations (400-1000 mgkg-1), not differing significantly (p > 0.05) from the controls and with tolerance index >1. T. ghanense and R. microsporus demonstrated exceptional capacity for Cd and As concentrations, while showing no significant (p > 0.05) difference compared to the controls and with a tolerance index >1 at 25 mgkg-1 Cd and 125 mgkg-1 As. Remarkably, these fungal strains showed tolerance to metal concentrations exceeding globally permissible limits for contaminated soils. It is envisaged that this metal tolerance trait exhibited by these fungal strains may indicate their potentials as effective agents for bioremediative clean-up of heavy metal polluted environments.

Draft genome sequence of Exiguobacterium aurantiacum strain PN47 isolate from saline ponds, known as "Salar del Huasco", located in the Altiplano in the North of Chile

ABSTRACT In this report, we present a draft genome of 2,886,173 bp of an Exiguobacterium aurantiacum strain PN47 isolate from the sediment of a saline pond named "Salar del Huasco" in the Altiplano in the North of Chile. Strain PN47 encodes adaptive characteristics enabling survival in extreme environmental conditions of high heavy metal and salt concentrations and high alkalinity.

Evaluation and enhancement of heavy metals bioremediation in aqueous solutions by Nocardiopsis sp. MORSY1948, and Nocardia sp. MORSY2014

ABSTRACT An analysis of wastewater samples collected from different industrial regions of Egypt demonstrated dangerously high levels of nickel (0.27-31.50 mg L-1), chromium (1.50-7.41 mg L-1) and zinc (1.91-9.74 mg L-1) in the effluents. Alarmingly, these heavy metals are among the most toxic knownones to humans and wildlife. Sixty-nine Actinomycete isolates derived from contaminated sites were evaluated under single, binary, and ternary systems for their biosorption capacity for Ni2+, Cr6+ and Zn2+ from aqueous solutions. The results of the study identified isolates MORSY1948 and MORSY2014 as the most active biosorbents. Phenotypic and chemotypic characterization along with molecular phylogenetic evidence confirmed that the two strains are members of the Nocardiopsis and Nocardia genera, respectively. The results also proved that for both the strains, heavy metal reduction was more efficient with dead rather than live biomass. The affinity of the dead biomass of MORSY1948 strain for Ni2+, Cr6+ and Zn2+ under the optimized pH conditions of 7, 8 and 7, respectively at 40 °C temperature with 0.3% biosorbent dosage was found to be as follows: Ni2+ (87.90%) > Zn2+ (84.15%) > Cr6+ (63.75%). However, the dead biomass of MORSY2014 strain under conditions of pH 8 and 50 °C temperature with 0.3% biosorbent dose exhibited the highest affinity which was as follows: Cr6+ (95.22%) > Ni2+ (93.53%) > Zn2+ (90.37%). All heavy metals under study were found to be removed from aqueous solutions in entirety when the sorbent dosage was increased to 0.4%.

Trace elements concentrations in Buff-breasted Sandpiper sampled in Lagoa do Peixe National Park, Southern Brazil / Concentração de elementos-traço em maçarico-acanelado amostrados no Parque Nacional da Lagoa do Peixe, Sul do Brasil

Abstract Cadmium, cobalt, chromium, copper, manganese, nickel, zinc and lead concentrations were detected in feathers of Buff-breasted Sandpipers (Calidris subruficollis) captured during the non-breeding season and analyzed with relationship to body mass. Of these metals tested for, only copper levels (2.28 µg/g) were positively correlated with bird body mass. Zinc levels showed higher concentration (67.97 µg/g) than the other metals, and cadmium levels showed the lowest concentration (0.14 µg/g). Trace element concentrations were below toxicity levels for all tested chemicals and we suggest that this probably reflects that essential elements are maintained there by normal homeostatic mechanism and that no excessive environmental exposure to these elements during migration or on the wintering area is suggested by these results.

Resumo As concentrações de cádmio, cobalto, cromo, cobre, manganês, níquel, zinco e chumbo foram detectadas em penas de Maçarico-acanelado (Calidris subruficollis) capturados durante o período de invernada e analisados em relação a massa corporal. Destes metais analisados, somente os níveis de cobre (2,28 µg/g) foram correlacionados positivamente com a massa corporal dos indivíduos. Níveis de zinco apresentaram-se mais altos (67,97 µg/g) que outros metais e os níveis de cádmio apresentaram as menores concentrações (0,14 µg/g). As concentrações dos elementos-traços estão abaixo dos níveis de toxicidade em todos os testes químicos e sugerimos que isto provavelmente ocorre pela manutenção dos elementos essenciais através do mecanismo normal de homeostase e não reflete a exposição destes elementos durante a migração ou nas áreas de invernada.

Plant Growth Promotion and Root Colonization by EPS Producing Enterobacter sp. RZS5 under Heavy Metal Contaminated Soil.

The heavy metal resistant bacterium isolated from field soil and identified as Enterobacter sp. RZS5 tolerates a high concentration (100-2000 mM) of various heavy metal ions such as Mn2+, Ni2+, Zn2+, Cu2+, CO2+ and Fe2+ when grown in such environment and produces exopolysaccharides (EPS). Here, we have demonstrated EPS production by Enterobacter sp. RZS5 during 60 h of growth in yeast extract mannitol broth (YEMB). The yield increased by two fold after the addition of 60 M of Ca2+; 50 M of Fe2+ and 60 M of Mg2+ ions in YEMB, and the optimization of physico-chemical parameters. EPS was extracted with 30% (v/v) of isopropanol as against the commonly used 50% (v/v) isopropanol method. EPS-rich broth promoted seed germination, shoot height, root length, number of leaves and chlorophyll content of wheat (Triticum aestivum) and peanut (Arachis hypogaea) seeds. The higher colony-forming unit of Enterobacter sp. in soil inoculated with EPS rich broth of Enterobacter sp. indicated the root colonizing potential and rhizosphere competence of the isolate. The FTIR spectra of the EPS extract confirmed the presence of the functional group characteristics of EPS known to exhibit a high binding affinity towards certain metal ions. This overall growth and vigour in plants along with the effective root colonization, reflected the potential of the isolate as an efficient bio-inoculant in bioremediation.

Bioavailability of pollutants in bacterial communities of Rodrigo de Freitas Lagoon, Rio de Janeiro, Brazil

Processes involving heavy metals and other contaminants continue to present unsolved environmental questions. To advance the understanding of geochemical processes that involve the bioavailability of contaminants, cores where collected in the Rodrigo de Freitas lagoon, and analyzed for bacterial activity and metal concentrations. Results would suggest an extremely reducing environment where organic substances seem to be the predominant agents responsible for this geochemical process. Analytical data showed sulphate reduction to be the main agent driving this process, since this kind of bacteria was found to be active in all of the samples analyzed. Esterase enzyme production did not signal the influence of heavy metals and hydrocarbon concentrations and heavy metals were found to be unavailable for biota. However, correlation between results for bacterial biomass and the potentially mobile percentage of the total Ni concentrations would suggest a negative impact.

Dynamic Cr(III) uptake by Macrocystis pyrifera and Undaria pinnatifida biomasses

Background: The increased industrial activity has resulted in the discharge of large amount of pollutants including non-degradable metals into the environment. Chromium is produced in several industrial processes and it can be found in the environment in two stable oxidation states, Cr(VI) and Cr(III). Cr(VI) is more hazardous due to its carcinogenic and mutagenic effects on living organisms. Although much less toxic, Cr(III) can also exert genotoxic effects under prolonged or severe exposure. It can be separated from the solution by precipitation but biosorption using brown algae seems to be an effective and sustainable treatment technique owing to its cost-effectiveness and environmental friendly characteristics. Macrocystis pyrifera and Undaria pinnatifida are two marine brown macroalgae with high capability of removing heavy metals including Cr(III) in batch mode of operation. In this work packed bed biosorption of Cr(III) by M. pyrifera and U. pinnatifida biomasses was evaluated. Results: The shapes of the breakthrough curves were rather different for each biomaterial. Parameters like the breakthrough time (t b) andzone mass transfer (MTZ) showed that U. pinnatifida has greater affinity for Cr(III). The maximum adsorption capacity at the exhaustion operating time (t e) demonstrated that M. pyrifera has higher retention capacity of Cr(III). The experimental data were fitted to Thomas, Yoon-Nelson and Dose-Response models. The best correlation coefficient (0.94 or 0.96) was obtained with Dose-Response that accurately describes the uptake behaviour of Cr(III) on the seaweed biomasses under different experimental conditions. The FT-IR spectra evidenced that Cr(III) adsorption occurred mainly by interaction between metal and carboxylate groups present on both the seaweed surfaces. Conclusions: M. pyrifera and U. pinnatifida biomasses are efficient biosorbents for Cr(III) adsorption under a continuous mode of operation although differences between uptake capacities suggest different mechanisms involved in the biosorption.

Physiological behavior of bean (phaseolus vulgaris l.) Seedlings under metal stress

The effects of nickel, cobalt, chromium and zinc on the content of vitamins A, E and C, malondialdehyde (MDA), chlorophyll and carotenoids were investigated in bean seedlings (Phaseolus vulgaris L.) grown in Hoagland solution Control and heavy metal-treated plants were grown for ten days in Hoagland solution. Vitamin A, E, and C content were measured in primary leaves by high performance liquid chromatographic (HPLC). MDA, chlorophyll and carotenoids were measured in leaves by spectrophotometer. In heavy metal treated plants, the levels of MDA, vitamins A, E and C and carotenoids significantly increased, while chlorophyll content decreased in leaves of seedlings. The results indicate that heavy metals caused an oxidative stress in bean plants. The strongest effect on vitamins A, E and C, MDA, chlorophyll and carotenoids was found in plants exposed to nickel, followed by the sequence cobalt > chromium> zinc.

Heavy metal tolerance (Cr, Ag and Hg) in bacteria isolated from sewage

Samples of sewage from a university hospital and a chemistry technical school were analysed for the percentage of bacterial tolerance to chromium (Cr), silver (Ag) and mercury (Hg). Additionally, we investigated the effect of these metals on pigmentation and on some enzymatic activities of the metal tolerant strains isolated, as well as antimicrobial resistance in some metal tolerant Enterobacteriaceae strains. Tolerance to Cr was observed mainly in Gram positive bacteria while in the case of Ag and Hg the tolerant bacteria were predominately Gram negative. Hg was the metal for which the percentage of tolerance was significantly higher, especially in samples from the hospital sewage (4.1%). Mercury also had the most discernible effect on color of the colonies. Considering the effect of metals on the respiratory enzymes, one strain of Ag-tolerantBacillus sp. and one of Hg-tolerant P. aeruginosa were unable to produce oxidase in the presence of Ag and Hg, respectively, while the expression of gelatinase was largely inhibited in various Gram negative strains (66% by Cr). Drug resistance in Hg-tolerant Enterobacteriaceae strains isolated from the university hospital sewage was greater than 80%, with prevalence of multiple resistance, while the Ag-tolerant strains from the same source showed about 34% of resistance, with the predominance of mono-resistance. Our results showed that, despite the ability of metal tolerant strains to survive and grow in the presence of these elements, the interactions with these metals may result in metabolic or phisiological changes in this group of bacteria.

Removal of heavy metals by exopolymeric substances produced by resistant purple nonsulfur bacteria isolated from contaminated shrimp ponds

Two purple nonsulfur bacteria (PNSB) strains, Rhodobium marinum NW16 and Rhodobacter sphaeroides KMS24 were investigated for their potential to remove heavy metals (HMs) from contaminated shrimp pond water. Tolerance of both PNSB strains growing with both microaerobic-light and aerobic-dark conditions, based on their minimum inhibitory concentrations, was in the order of Cu2+ > Zn2+ > Cd2+ (Pb precipitation occurred at 0.34 mM). Results from a scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDX) indicated that Cu2+ and Zn2+ altered the cellular morphology of both strains and accumulated HMs were found in their cells. The highest amounts of both cations were found in their cell walls followed by the cytoplasm and cell membrane. Using the highest concentrations (mM) of HMs found in shrimp pond of 0.0067 Cd2+, 0.54 Cu2+, 0.30 Pb2+, 0.89 Zn2+ and 3 percent NaCl under both incubating conditions exopolymeric substances (EPS) produced by both strains showed a greater removal of all HMs (average percentages; 90.52-97.29) than their cells (average percentages; 14.02-75.03).

Metal contamination in benthic macroinvertebrates in a sub-basin in the southeast of Brazil / Estudo da contaminação por metal em macroinvertebrados bentônicos em uma sub-bacia do sudeste do Brasil

Benthic macroinvertebrates have many useful properties that make possible the use of these organisms as sentinel in biomonitoring programmes in freshwater. Combined with the characteristics of the water and sediment, benthic macroinvertebrates are potential indicators of environmental quality. Thus, the spatial occurrence of potentially toxic metals (Al, Zn, Cr, Co, Cu, Fe, Mn and Ni) in the water, sediment and benthic macroinvertebrates samples were investigated in a sub-basin in the southeast of Brazil in the city of São Carlos, São Paulo state, with the aim of verifying the metals and environment interaction with benthic communities regarding bioaccumulation. Hypothetically, there can be contamination by metals in the aquatic environment in the city due to lack of industrial effluent treatment. All samples were analysed by the USEPA adapted method and processed in an atomic absorption spectrophotometer. The sub-basin studied is contaminated by toxic metals in superficial water, sediment and benthic macroinvertebrates. The Bioaccumulation Factor showed a tendency for metal bioaccumulation by the benthic organisms for almost all the metal species. The results show a potential human and ecosystem health risk, contributing to metal contamination studies in aquatic environments in urban areas.

Os organismos bentônicos têm muitas propriedades úteis que os fazem organismos sentinelas em programas de biomonitoramento em ecossistemas de água doce. Analisando em conjunto com as características da água e do sedimento, são potenciais indicadores da qualidade ambiental. Neste contexto, a ocorrência espacial de metais pesados (Al, Zn, Cr, Co, Cu, Fe, Mn e Ni) na água, sedimentos e amostras de macroinvertebrados bentônicos foi investigada em uma sub-bacia no sudeste do Brasil, na cidade de São Carlos, SP, com o objetivo de verificar a interação dos metais do ambiente com a comunidade bentônica quanto à bioacumulação. Por hipótese, admite-se que haja contaminação por metais nos ambientes aquáticos do município devido à ausência de tratamento de efluentes industriais. Todas as amostras foram analisadas pelo método USEPA adaptado e processado por espectrofotômetro de absorção atômica. A bacia estudada apresenta contaminação por metais tóxicos em águas superficiais, sedimentos e macroinvertebrados bentônicos. O Fator de Bioacumulação mostrou uma tendência para a bioacumulação de metais por organismos bentônicos para quase todas as espécies de metal. Os resultados demonstram um potencial risco à saúde humana e ao ecossistema, contribuindo com o estudo de contaminação por metais em ambientes aquáticos de áreas urbanas.

Glutathione and cysteine biosynthesis in two varieties of Abelmoschus esculentus in response to mine spoil.

The extent of accumulation of some heavy metals and glutathione and cysteine levels in the roots and aerial plant parts in two genotypically different varieties of A. esculentus (KS404 and BO2) exposed to mine spoil were investigated. Glutathione (GSH) level in both the varieties on control sites increased from basal level to 155.15 nmol g(-1) dry weight (d.wt.), almost 1.5 fold on 30 day and attained a plateau within 60 day Mine spoil exposure of both the varieties decreased glutathione 1.13 fold (89.2 nmol g(-1) dry weight) during 60 day from its basal level. GSH concentration in shoots of these varieties increased accompanying growth contrary to roots where it finally declined 2 fold. Cysteine content in control plants increased 2 fold (31.6 nmol g(-1) dry weight) on 30 day and finally declined 1.38 fold (22.35 nmol g(-1) dry weight, at 60 day). Both the varieties, when exposed to mine spoil, showed enhanced cysteine content almost 2 fold during 30 day (50.95 nmol g(-1) dry weight) but failed to increase further Forshoots in both the varieties challenged with mine spoil, cysteine maxima reached late (15.2 nmol g(-1) dry weight, at 40 day) relative to control but the levels declined subsequently (11.85 nmol g(-l) dry weight). Contrary to GSH, cysteine content in roots of both the varieties responded positively to mine spoil as apparent from the 2.23 fold increase during 30 d than basal level although it lowered to a level of 12.85 nmol g(-1) dry weight finally at 60 day. Both the varieties accumulated almost maximum level of selected cations (Fe > Mn> Zn> Cu > Ni) during 30 day, but BO2 variety was significantly superior in this regard. Invariably high accumulation of such cations in roots over shoots indicated accumulation, retention or restricted translocation from root to shoot. The metal share of the edible part was just 6% of the plant load. Thus, present work reflects a genotypic differences in metal accumulation and that affected the major non-enzymatic traits or synthesis of sulthydryl compounds as well. The present results also indicate that metal tolerance is in part associated with anti-oxidant system activity.

Accumulation of heavy metals (Cd, Cr, Cu, Ni and Zn) in Raphanus sativus L. and Spinacia oleracea L. plants irrigated with industrial effluent.

Effluent from electroplating industry contains various heavy metals like Cd, Cr, Cu, Ni and Zn, which are used in electroplating process of industry. Effluent was slightly greenish in colour and pungent in odour. Physico-chemical properties like total suspended solids (TSS), total solids (TS), alkalinity, Biological oxygen demand (BOD), and Chemical oxygen demand (COD) showed higher values in effluent with high metal contents like Cd, 0.013; Cr, 0.093; Ni, 0.935 and Zn 4.76 mg l(-1). plants of S. oleracea and R. sativus were raised in uncontaminated alluvial soil of Lucknow by soil pot culture method and irrigated with industrial effluent, showed visual toxic symptoms like stunted growth, necrosis followed by chlorosis in leaves and finally death of the plants. Severity of toxicity was less in plants treated with diluted effluent (50%). High accumulation of Cr, 302.0; Cu, 81.2; Ni, 155.1 and Zn 146.8 microg g(-1) dry weight in S. oleracea and Cr, 198.0; Cu, 41.0; Ni, 84.3 and Zn, 140.2 microg g(-1) dry weight in R. sativus were determined. Tissue concentration of metals and toxic effects was more in S. oleracea plants. The tissue concentration of metals showed much higher values in treated plants than that of their respective control.

Biosorption of Ni, Cr and Cd by metal tolerant Aspergillus niger and Penicillium sp. using single and multi-metal solution.

Fungi including Aspergillus and Penicillium, resistant to Ni2+, Cd2+, and Cr6+ were isolated from soil receiving long-term application of municipal wastewater mix with untreated industrial effluents of Aligarh, India. Metal tolerance in term of minimum inhibitory concentration (MIC) was 125-550 microg/ml for Cd, 300-850 microg/ml for Ni and 300-600 microg/ml for Cr against test fungi. Two isolates, Aspergillus niger and Penicillium sp. were tested for their Cr, Ni and Cd biosorption potential using alkali treated, dried and powdered mycelium. Biosorption experiment was conducted in 100 ml of solution at three initial metal concentrations i.e., 2, 4 and 6 mM with contact time (18 hr) and pretreated fungal biomass (0.1g) at 25 degrees C. Biosorption of all metals was found higher at 4 mM initial metal concentration as compared to biosorption at 2 and 6 mM concentrations. At 4 mM initial metal concentration, chromium biosorption was 18.05 and 19.3 mg/g of Aspergillus and Penicillium biomasses, respectively. Similarly, biosorption of Cd and Ni ions was also maximum at 4 mM initial metal concentration by Aspergillus (19.4 mg/g for Cd and 25.05 mg/g of biomass for Ni) and Penicillium (18.6 mg/g for Cd and 17.9 mg/g of biomass for Ni). In general, biosorption of metal was influenced by initial metal concentration and type of the test fungi. The results indicated that fungi of metal contaminated soil have high level of metal tolerance and biosorption properties.

Seasonal pattern of metal bioaccumulation and their toxicity on Sphagnum squarrosum.

Present study was undertaken as an attempt to study the effect of pollutants on biological responses of Sphagnum growing at Kainchi, Kumaon hills (Uttranchal). Sphagnum plants of almost identical size, collected from the marked sites of Kainchi in different seasons viz., monsoon, winter, summer and again in monsoon, were analysed for chlorophyll, protein, shoot length and nitrate reductase and peroxidase activities. Maximum chlorophyll, protein, shoots length and nitrate reductase activities were observed during the monsoon while minimum in summers. The abundance of Sphagnum and two other bryophytes, Marchantia and Plagiochasma was also higher in monsoon than in other seasons. The study also indicated that Sphagnum has more bioaccumulation and tolerance potential for heavy metals than Marchantia and Plagiochasma.

Biological effects of heavy metals: an overview.

Heavy metals constitute a very heterogeneous group of elements widely varied in their chemical properties and biological functions. Heavy metals are kept under environmental pollutant category due to their toxic effects on plants, animals and human being. Heavy metal contamination of soil results from anthropogenic as well as natural activities. Anthropogenic activities such as mining, smelting operation and agriculture have locally increased the levels of heavy metals such as Cd, Co, Cr, Pb, As and Ni in soil up to dangerous levels. Heavy metals are persistent in nature, therefore get accumulated in soils and plants. Heavy metals interfere with physiological activities of plants such as photosynthesis, gaseous exchange and nutrient absorption, and cause reductions in plant growth, dry matter accumulation and yield. Heavy metals also interfere with the levels of antioxidants in plants, and reduce the nutritive value of the produce. Dietary intake of many heavy metals through consumption of plants has long term detrimental effects on human health.