جستجوی مقالات مرتبط با کلیدواژه « جیوه » در نشریات گروه « زیست شناسی »

Nowadays, heavy metals pollution is one of the most important environmental problems. Due to the high cost of common refining methods, the use of microbial biomass is recommended to clean up heavy metals. The aim of this study was the evaluation of interactions of Rhodoterula toruloides strain IR-1395 with mercury.

In this study, the growth rate and interactions of strain IR-1395 with mercury in Sucrose Broth medium were investigated and the amount of mercury accumulated was measured using the Spectrophotometry method. Then, in order to determine the best biosorption conditions, the effect of parameters such as pH, mercury concentration, biomass concentration, contact time and temperature were measured. Also, the biosorption was investigated by treated cells with 2, 4 dinitrophenol and autoclave. Finally, the biosorbent was characterized by Scanning Electron Microscope with Energy Dispersive X-Ray Analysis.

Studies showed that the maximum growth rate of strain IR-1395 was after 36h and then it enters the stationary phase. Also, this strain was able to the biosorption and bioaccumulation (61.86%) and 10.17% biovolatilization of mercury from the medium at the concentration of 10 mg/l of chloride mercury during seven days. In study of factors affecting on the mercury biosorption, it is indicated that the optimal pH was 4. The highest biosorption was observed at 300 mg /l of mercury in 10 minutes at 15 ˚C. Mercury adsorption using treated biomass by autoclaved and 2,4 dinitrophenoltreatment has reduced than control samples. Finally, the results of the EDX confirmed the biosorption of mercury by this yeast.

By study of the various interactions of strain IR-1395 with mercury and its potential in biosorption, it was found that this strain is a valuable microorganism in mercury bioremediation processes from contaminated aquatic environments.

In the study, the mercury concentrations in water, sediment and plankton in Khor Musa was investigated. The 9 samples of water and sediment were collected from each estuary and a total of 45 samples were taken. Sampling of phytoplankton and zooplankton was collected by net of 20 and 300 µm, respectively. After the concentrations of mercury by cold vapour method was measured using atomic absorption. The results showed that mercury concentrations range from 4.39±0.82 (mean±SE) to 11.66±2.14 µg/L in water and 0.26±0.03 to 0.76±0.04 µg/g of dry weight in sediments. The mercury concentrations 0.02±0.01 To 0.17±0.01 on phytoplankton and 0.10±0.01 to 0.47±0.07 µg/g for zooplankton were measured. The correlation factors showed that mercury concentrations in phytoplankton and zooplankton had significant positive correlation (P <0.05). With the mercury rising mercury concentrations in zooplankton increases in phytoplankton due to the high toxicity of mercury, the possibility of bioaccumulation and bio-magnification in the aquatic organisms and contamination of the waters in the estuary Moses regular monitoring is essential to ensure the health of ecosystems. Therefore, in this study to determine the amount of mercury in low levels of the food, chemical concentrations in water, sediments and plankton were measured in the estuary area of Khor Musa.

Mercury (T-Hg), as the most toxic Trace metal, can have adverse effects on the environment. In this study, the concentrations of T-Hg were investigated in surface sediments of higher and lower tidal zones of Hormozgan province coasts including the stations of Shahr Jask, Ariyan International Wetland Lagoon, Khorgorsuzan Bandar Abbas, Bostono Industrial Zone, Coastal Park of Khumir, Shahrbonderlangeh, Bandarreqam, Bostaneh Harbor in summer 2017. T-Hg concentration was measured by Ftomic Atomic Aabsorption Spectrometry (FAAS, GTA120). From 16 stations in the higher and lower tidal zones, the stations of Khorgorsuzan Station and Azzin kinetic showed the lowest concentration of T-Hg. Based on accumulation index (Igeo), the geochemistry of the Igeo studied areas had a moderate to high contamination. Enrichment Factor (EF) showed a strong to extremely high enrichment. Regarding SQGS, all stations were higher than Effect Range Low (ERL) value. These findings raise awareness of the contamination status of surface sediments in coastal zone of Hormozgan Province, provide a valuable benchmark for future comparisons in the area, and are important for the design of appropriate policies and long-term management of those ecosystems by local managers and the national authorities.

Inorganic mercury entrance into the environment through industry and agriculture is one of the most serious environmental hazards in the country. Microbial bioremediation is considered as one of the practical solutions to clean up pollutant ions from the environment. The present study was conducted to construct a recombinant vector including merA gene, and also to investigate its expression in order to clean up mercury.
Material & merA gene from mercury resistance bacterial genome was isolated, and subsequently cloned into the pET21a() expression vector. Confirmation of cloning target gene was achieved by PCR and restriction enzyme digestion. Then pET21a()-merA recombinant vector was cloned into E.coli strain BL21. In order to assess increased resistance to mercury in recombinant bacteria, and the functionality of the enzyme produced by the recombinant vector, the growth rate of recombinant BL21 E. coli strains to contain merA gene, and without it was measured in a medium containing mercury for 48 hours.
The results showed that the growth of E. coli strains without merA gene was strongly affected after introducing mercury into the media till 12 hours, and bacteria would not be able to grow at 10 ppm and 20 ppm mercury levels. However, transformed bacteria with pET21a()-merA vector showed suitable growth in mercury-containing media. SDS-PAGE analysis of recombinant bacterial proteins on acrylamide gel showed the highest MerA (62KDa) expression following 16 hours induction with 1mM IPTG at 37ºC.
Overall, the growth ability of merA- containing recombinant bacteria reflects the action of MerA protein in transformed bacteria. Furthermore, increasing the resistance of recombinant bacteria to the mercury indicates that environmental heavy metal pollutants can be cleaned up properly through the construction of recombinant vectors.

In this study, the levels of heavy metals concentration (mercury, zinc, copper, cadmium and lead) were measured in the feathers, egg contents and eggshells of Larus genei from Musa Estuary. For this purpose, twenty eggs and fifteen Larus genei were collected at the locations during 2013. To do the process, after drying and digestion of samples, the concentration of mercury in samples was measured by cold vapor. In general, except for Pb, the level of whole metals in feathers was higher than egg contents and eggshells. The metal concentrations in feathers were according to the following order Zn> Hg > Cu > Pb> Cd, in egg contents were Zn> Cu > Hg > Pb> Cd and in eggshells were Pb > Zn > Cu > Cd > Hg. Also, comparing our results with the standard of World Health Organization, we found that mercury levels in in feathers and eggs of Larus genei were flying above mentioned standards. High accumulation of mercury in the feathers and eggs has likely originated from mercury sources such as petrochemical plants.

Mercury is one of the polluting sources of the environment, plants as well as human. Microorganisms are resistant to mercury through different mechanisms. The main mechanism involves reduction of the toxic mercury to the elemental form which is mediated through a variety of bacterial genes. The aim of this study is to investigate the presence of mercury resistance gene in Raoultella planticula bacteria using polymerase chain reaction (PCR) and sequencing methods.
Genomic and plasmid DNA was extracted from wastewater R. planticula isolates. PCR was set up with primers designed based on the presence of mer A gene in Klebsiella oxytoca. The PCR products were sequenced and analyzed using NCBI database.
Using PCR on plasmid and genomic bacterial DNA, a 1700 bps bond was obtained. Blasting the sequence, it was found that the amplified gene has 99% sequence homology to merA gene in Enterobacter cloacae, E. coli, Serratia marcescens, Klebsiella oxytoca and Acinetobacter.
For the first time in this study, we found that Raoultella planticula isolated from Iran natural sources are resistant to mercury due to the presence of merA gene. Therefore, R. planticula can be considered an appropriate candidate to reduce or remove mercury from industrial wastewaters.

Rotifers due to their relatively short lifespan, high fecundity and high rate of population increase are ideal for chronic toxicity tests. Mercury is one of the heavy metals highly toxic to aquatic organismsparticulary freshwater zooplankton of which rotifers are an important group. In peresentstudy, population response of rotifer B. calyciflorus to six different concentrations of mercury (0.0005, 0.001, 0.002, 0.004, and 0.008 mgL-1) with three replicates per concentration was studied for 12 days. Rotifer density and specific growth rate was calculated daily in the control and treatments containing mercury. Result showed that, rotifer population growth decreased significantly (p

Inroduction & Heavy metals accumulate in various tissues and by lack of degradation, could be gradually stored in the fatty tissues of the human body and can cause acute and chronic diseases. In this study, the relationship between body weight of fish and heavy metals such as lead and mercury in muscle of rainbow trout (Oncorhynchus mykiss) cultured in the farms of the Dohezar river was measured and compared with international standards WHO.
Twenty cultured rainbow trout reared in a fish farm of Dohezar River (weight range 30 to 410 g) were randomly sampled. Determination of lead and mercury was measured by atomic absorption in a correlation study.
Average lead and mercury concentrations in farmed rainbow trout were equal to 0.107 and 0.022 micrograms per gram of muscle, respectively. The correlation coefficient between fish weight and lead level (r= 0.243, P= 0.301) and mercury level were (r= -0.204, P= 0.388).
The fish body weight had no effect on the lead and mercury level in the muscle (P > 0.05). Also the lead and mercury levels measured in the muscle of rainbow trout in the present study are lower than the acceptable WHO standards which indicate fish are safe for human consumption in this river.

Studies have shown that birds due to being in the high trophic levels on the ecosystems, and also high sensitivity to toxic substances are a useful indicator for the evaluation of mercury pollution. The objective of the present study was to evaluate mercury level in the feathers of Turdus philomelos and Turdus merula in khanikan forests as an indicator of mercury contamination. To attain this aim, 37 samples belonging to two species were collected from khanikan forests, located in southern part of Noushahr and Chalous cities. Feather samples were removed in the lab. Level of mercury was determined by Mercury Analyzer AMA 254. Statistical analyses were performed using SPSS software. According to the results of this study, mercury levels in feathers of Turdus philomelos (0.98 µg/g) and Turdus merula (0.94 µg/g) was too lower than standard limit (5 µg/g), and also there was no significant difference between two species in terms of mercury level. These results showed that habitat of these species were not heavily polluted by mercury. According to biomagnification of mercury in trophic levels, can be concluded that because of seed eating habits of Turdus philomelos and Turdus merula, low levels of mercury accumulated in feathers of these species

This study was done to determine the mercury concentration in the surficial sediments from the Musa Estuary. 5 creeks including Zangi, Jafari, Petroshimi, Ghazaleh and Majidieh were selected and a total number of 9 sediment samples were collected from each creak. Sampling was performed in November 2009. Mercury concentrations were measured by cold vapor atomic absorption spectrophotometer, after digesting of the samples. The mercury concentrations in the sediments ranged from 0.31 to 0.69 µg/g. The highest Hg contents were found in the Petroshimi estuary followed by Majidieh estaury, probably due to the effluent inputs from Bandar Imam Chloralkali petrochemical plant, oil spills and Navigation and shipping related activities. Regarding the contamination factor at regional level, the studied estauries are classified as a considerably polluted area, but at global scale, contamination factor shows low to moderate degree of pollution in them.

In this study، the bioaccumulation of mercury and cadmium in the soft tissue of Crassostrea sp. were studied at experimental conditions. Also، the bioaccumulation trend of Hg and Cd in oysters were analyzed and compared during exposure period. The oysters collected from harbor No. 28 in the coast of Imam Khomeini port had lowest pollution of Hg and Cd according to the last studies. After 7 days of acclimation in laboratory، the oysters exposed to Hg at concentrations of 15 and 75 μ􀝃. 􀝈-1 and Cd at concentrations of 15 and 150 μ􀝃􀝈-1 for 14 days. Heavy metal contents in oysters were measured by atomic absorption per 48 hours. Results indicated that the Hg bioaccumulation in bivalve soft tissue was faster and stronger than Cd bioaccumulation، despite the fact that Hg had lower concentration in the experiment. The maximum bioaccumulation of metals in bivalves soft tissue was 107. 6±6. 7 μ􀝃. 􀝃-1 Hg and 86. 5±7. 6 μ􀝃. 􀝃 Cd at experimental dose of 75 μ􀝃. 􀝈-1 Hg and 150 μ􀝃. 􀝈-1 Cd، respectively.

Movement of water across cellular membranes is facilitated by the presence of water channels named aquaporins (AQPs). Mercurial compounds are potent blockers of plant and animal aquaporins. However some aquaporin isoforms such as NtAQP1 in tobacco are mercury-insensitive. The aim of this research was to determine the sensitivity of tobacco NtPIP2;1 to mercury. In this experimental study, after invitro transcription of NtPIP2;1 and cRNA synthesis, cRNA was injected to Xenopus oocytes by microinjection. Two days after incubation, oocytes were subjected to 1 mM mercury chloride for 10 min. Then, oocyte volume swelling assay in hypotonic medium was conducted and the membrane osmotic water permeability coefficient (Pf) was determined. Pf for control and mercury chloride-treated oocytes expressing NtPIP2;1 was respectively calculated 0.99×10-2 and 0.98×10-2 cm s-1, which was not significant (P>0.05). Comparing the amino acid sequence of NtPIP2;1 with NtAQP1, a mercury-insensitive aquaporin, revealed the similar to NtAQP1 replacement of cys with Thr in 233 position near the aquaporin pore in NtPIP2;1. NtPIP2;1 encodes a mercury-insensitive aquaporin in tobacco which could be due to cysteine replacement with threonin near the aquaporin pore.

A series of specific toxicological effects including bioaccumulation of the pollutant, histological changes and influences on muscle tissue were examined in the Roach fish (Rutilus rutilus) after the exposure to graded sub lethal concentrations (10, 30, 50 μg Hg/L) of mercury chloride (MC). Histopathological changes, such as telangiectasis, and degenerative, can clearly be observed in the slices from the muscle exposed Roach. A batch of Roach with the mean values of 5 cm in length and 5.5 g in mass were pre-raised in a static system, which was supplied with dechlorinated tap water and constantly aerated. The water qualities were controlled as follows: pH, 7.45; oxygen concentration, 7 mg/L; the water temperature, 21–22 ◦C. All fish were fed twice a day with a commercial ratio of biomar. Reagents appropriate amount of mercury chloride (MC, AR 98%, Merck-Schuchardt) was dissolved in a stock solution of 0.676g HgCl2/L. Based on the 24 h LC50 value (70 ppb) obtained from the acute exposure test, a graded series (10, 30, 50 μg Hg/L) of mercury chloride (MC) were administered to Roach fish (Rutilus rutilus) with 48 fish per group. The chemical exposure experiments lasted for 48, 96 and 144 hours. These designed exposure levels were sublethal, and could induce obvious alteration of tissues abnormalities and disease at the same time.