This document summarizes the work of Sayan Sarkar on isolating and characterizing arsenic-tolerant bacteria from soil and water samples. Three bacterial strains, CRS2, CRS4, and CMW3, were isolated that could grow in media containing high concentrations of arsenic. Initial tests showed the strains were Gram negative, and CRS4 and CMW3 tested positive for catalase. A soil-water study found the strains could mobilize arsenic from soil into water. Further sequencing and analysis of the strains' arsenic transformation abilities is planned to understand their potential for bioremediating arsenic-contaminated environments.
Biominerals and waxes of Calamagrostis epigejos and Phragmites australis leav...EdytaSierka
Protoplasma, 2018
Vascular plants are able to conduct biomineralization processes and collect synthesized compounds in their internal tissues or to deposit them on their epidermal surfaces. This mechanism protects the plant from fluctuations of nutrient levels caused by different levels of supply and demand for them. The biominerals reflect both the metabolic characteristics of a vascular plant species and the environmental conditions of the plant habitat. The SEM/EDX method was used to examine the surface and cross-sections of the Calamagrostis epigejos and Phragmites australis leaves from post-industrial habitats (coal and zinc spoil heaps). The results from this study have showed the presence of mineral objects on the surfaces of leaves of both grass species. The calcium oxalate crystals, amorphous calcium carbonate spheres, and different silica forms were also found in the inner tissues. The high variety of mineral forms in the individual plants of both species was shown. The waxes observed on the leaves of the studied plants might be the initializing factor for the crystalline forms and structures that are present. For the first time, wide range of crystal forms is presented for C. epigejos. The leaf samples of P. australis from the post-industrial areas showed an increased amount of mineral forms with the presence of sulfur.
DOI:10.21276/ijlssr.2016.2.4.9
and so pollutant burdens recorded in soft body tissue, bones, feathers and eggs are likely to reflect chemical contamination
within their extended home ranges. These local, upper trophic level species are believed to be especially vulnerable to
metals and play a very important role as environmental contamination indicators. The concentration of Lead (Pb),
Cadmium (Cd), Copper (Cu), Zinc (Zn) and Iron (Fe) were determined in feather samples of Long-billed vultures (Gyps
indicus) (n = 100) collected from Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna Districts of Bundelkhand Region
during 2007-2011. Sample preparation and analyses of metals were performed in the Indian Veterinary Research Institute,
Izatnagar, Bareilly. Metal level in the samples was analyzed by Atomic Absorption Spectrophotometer (AAS 4141,
ECIL, Hyderabad, India) wavelength of 229.5 nm (detection limit 0.005 μg/mL) and 217 nm (detection limit 0.025
μg/mL), respectively with 6mA current. The concentration of Cd, Pb, Cu, Zn and Fe determined in all the feathers
collected from five sites was within the range of 0.1μg/g-0.4 μg/g, 0.47μg/g-6.4 μg/g, 2.9μg/g- 8.11μg/g, 9 μg/g- 21.4
μg/g and 18.3μg/g- 194.9μg/g respectively According to ANOVA test, significant differences (0.05) were found for metals
(Pb, Cd, Cu, Zn and Fe) in all feathers from Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna. When the metal toxicity
results in feathers were seen district wise (Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna) no significant variance
were reported in the occurrence of metals. No significant relationships were found between the metals in feather sample
concentrations and their death. It can therefore be concluded that the metal concentrations are much below the lethal toxic
levels and had no affect on the health of the dead vultures. The results of this study allowed concluding that the
Long-billed vultures in the study area were not exposed to metal poisoning. The absence of linkage between the metal
toxicity and vulture mortalities is not unexpected when consulted with other previous studies. Key-words- Long-billed vultures, Feathers, Lead, Cadmium, Copper, Zinc, Iron
Biominerals and waxes of Calamagrostis epigejos and Phragmites australis leav...EdytaSierka
Protoplasma, 2018
Vascular plants are able to conduct biomineralization processes and collect synthesized compounds in their internal tissues or to deposit them on their epidermal surfaces. This mechanism protects the plant from fluctuations of nutrient levels caused by different levels of supply and demand for them. The biominerals reflect both the metabolic characteristics of a vascular plant species and the environmental conditions of the plant habitat. The SEM/EDX method was used to examine the surface and cross-sections of the Calamagrostis epigejos and Phragmites australis leaves from post-industrial habitats (coal and zinc spoil heaps). The results from this study have showed the presence of mineral objects on the surfaces of leaves of both grass species. The calcium oxalate crystals, amorphous calcium carbonate spheres, and different silica forms were also found in the inner tissues. The high variety of mineral forms in the individual plants of both species was shown. The waxes observed on the leaves of the studied plants might be the initializing factor for the crystalline forms and structures that are present. For the first time, wide range of crystal forms is presented for C. epigejos. The leaf samples of P. australis from the post-industrial areas showed an increased amount of mineral forms with the presence of sulfur.
DOI:10.21276/ijlssr.2016.2.4.9
and so pollutant burdens recorded in soft body tissue, bones, feathers and eggs are likely to reflect chemical contamination
within their extended home ranges. These local, upper trophic level species are believed to be especially vulnerable to
metals and play a very important role as environmental contamination indicators. The concentration of Lead (Pb),
Cadmium (Cd), Copper (Cu), Zinc (Zn) and Iron (Fe) were determined in feather samples of Long-billed vultures (Gyps
indicus) (n = 100) collected from Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna Districts of Bundelkhand Region
during 2007-2011. Sample preparation and analyses of metals were performed in the Indian Veterinary Research Institute,
Izatnagar, Bareilly. Metal level in the samples was analyzed by Atomic Absorption Spectrophotometer (AAS 4141,
ECIL, Hyderabad, India) wavelength of 229.5 nm (detection limit 0.005 μg/mL) and 217 nm (detection limit 0.025
μg/mL), respectively with 6mA current. The concentration of Cd, Pb, Cu, Zn and Fe determined in all the feathers
collected from five sites was within the range of 0.1μg/g-0.4 μg/g, 0.47μg/g-6.4 μg/g, 2.9μg/g- 8.11μg/g, 9 μg/g- 21.4
μg/g and 18.3μg/g- 194.9μg/g respectively According to ANOVA test, significant differences (0.05) were found for metals
(Pb, Cd, Cu, Zn and Fe) in all feathers from Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna. When the metal toxicity
results in feathers were seen district wise (Tikamgarh, Lalitpur, Shivpuri, Chanderi and Panna) no significant variance
were reported in the occurrence of metals. No significant relationships were found between the metals in feather sample
concentrations and their death. It can therefore be concluded that the metal concentrations are much below the lethal toxic
levels and had no affect on the health of the dead vultures. The results of this study allowed concluding that the
Long-billed vultures in the study area were not exposed to metal poisoning. The absence of linkage between the metal
toxicity and vulture mortalities is not unexpected when consulted with other previous studies. Key-words- Long-billed vultures, Feathers, Lead, Cadmium, Copper, Zinc, Iron
Mineral-deficient states largely occur in humans and animals because of the nutrition
imbalance. One of the criteria of low copper content in food is a feature of the geological
province which produces agricultural products [4]. One of the criteria of the cell
elemental status regulation of an organism can be associated with the use of probiotic
microorganisms that possess not only high sorption characteristics but also are able to
deposit excessive content of essential elements in the biologically active form. To assess
the perspectives of the application of probiotic microorganisms of the genus Bacillus as
micronutrients we used such methods as the agar basin method relating to diffusion
Atmospheric Exposure to Cr III Powder Causes Genotoxicity in Rattus Norvegicus.inventionjournals
Several chemical elements are responsible for altering the genetic integrity of living beings. The metal Cr stands out in this regard. It exists in two oxidation states, Cr VI and Cr III, and has been investigated as an important environmental and occupational contaminant. Although the former is considered carcinogenic, the latter is classified as safe, even for human use in food supplementation. However, most studies with Cr( III) have been carried out by different routes to how it is occupationally found – in the atmosphere. This study evaluated the genotoxicity of Cr(III) inhaled during 8 hours of exposure to the maximum concentration permitted by ATSDR. Fifteen male Rattus norvegicus were used in this study. There were 3 groups (n=5 per group); these were - group exposed to Cr (III) powder (S), the negative control group (NC) and the positive control group (PC). The animals were exposed to Cr aerosol particles at a flow rate of 9L/min and atmospheric concentration of 500μg/m3 for only 8 hours in this study. An increase in genotoxicity and mutagenicity in the group exposed to the metal powder was observed. These findings suggest that further studies should be carried out in order to establish safe levels of exposure to Cr III in work environments
Isolation and Characterization of Nickel Tolerant Bacterial Strains from Elec...Agriculture Journal IJOEAR
Abstract— In the present study, an attempt was made to isolate and characterize nickel tolerant bacterial strains from the electroplating effluent contaminated soil. The effluent sample was collected at the direct outlet of electroplating industry and analyzed for physico-chemical characteristics such as pH (6.5), temperature (33), electrical conductivity (15.1 ms/cm), total solids (2309mg/l), total dissolved solids (5573 mg/l), chloride (0.20mg/l), sodium (0.13ppm), calcium (2.23ppm), potassium (0.20ppm), Biological Oxygen Demand (4200mg/l), Chemical Oxygen Demand (5243 mg/l) and nickel (4.063ppm). Enumeration of total bacterial population from the electroplating effluent contaminated soil sample was made in nutrient agar medium. Sixteen bacterial colonies were selected based on their abundance growth all of them were identified through morphological and biochemical characteristics. All the sixteen bacterial isolates were screened for its metal tolerance using nutrient agar medium incorporated with nickel metal. Based on the better growth performance, six bacterial strains were selected as potential metal tolerant organism. The selected metal tolerant bacterial strains were further characterized in the various environmental conditions such as pH (5, 7 & 9) temperature (5°C, 28°C, 37°C & 45°C) and concentration of metal ions (100ppm, 200ppm, 300ppm & 400ppm) for 5 days. The result reveals that one bacterial strain, Pseudomonas sp 1 was showed better growth in nickel metal based medium with pH 7 at 37°C temperature.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Determination of Arsenic, Chromium,Selenium and Zinc in fish samples of Bangladesh has been described and compared with the results published elsewhere.
Mineral-deficient states largely occur in humans and animals because of the nutrition
imbalance. One of the criteria of low copper content in food is a feature of the geological
province which produces agricultural products [4]. One of the criteria of the cell
elemental status regulation of an organism can be associated with the use of probiotic
microorganisms that possess not only high sorption characteristics but also are able to
deposit excessive content of essential elements in the biologically active form. To assess
the perspectives of the application of probiotic microorganisms of the genus Bacillus as
micronutrients we used such methods as the agar basin method relating to diffusion
Atmospheric Exposure to Cr III Powder Causes Genotoxicity in Rattus Norvegicus.inventionjournals
Several chemical elements are responsible for altering the genetic integrity of living beings. The metal Cr stands out in this regard. It exists in two oxidation states, Cr VI and Cr III, and has been investigated as an important environmental and occupational contaminant. Although the former is considered carcinogenic, the latter is classified as safe, even for human use in food supplementation. However, most studies with Cr( III) have been carried out by different routes to how it is occupationally found – in the atmosphere. This study evaluated the genotoxicity of Cr(III) inhaled during 8 hours of exposure to the maximum concentration permitted by ATSDR. Fifteen male Rattus norvegicus were used in this study. There were 3 groups (n=5 per group); these were - group exposed to Cr (III) powder (S), the negative control group (NC) and the positive control group (PC). The animals were exposed to Cr aerosol particles at a flow rate of 9L/min and atmospheric concentration of 500μg/m3 for only 8 hours in this study. An increase in genotoxicity and mutagenicity in the group exposed to the metal powder was observed. These findings suggest that further studies should be carried out in order to establish safe levels of exposure to Cr III in work environments
Isolation and Characterization of Nickel Tolerant Bacterial Strains from Elec...Agriculture Journal IJOEAR
Abstract— In the present study, an attempt was made to isolate and characterize nickel tolerant bacterial strains from the electroplating effluent contaminated soil. The effluent sample was collected at the direct outlet of electroplating industry and analyzed for physico-chemical characteristics such as pH (6.5), temperature (33), electrical conductivity (15.1 ms/cm), total solids (2309mg/l), total dissolved solids (5573 mg/l), chloride (0.20mg/l), sodium (0.13ppm), calcium (2.23ppm), potassium (0.20ppm), Biological Oxygen Demand (4200mg/l), Chemical Oxygen Demand (5243 mg/l) and nickel (4.063ppm). Enumeration of total bacterial population from the electroplating effluent contaminated soil sample was made in nutrient agar medium. Sixteen bacterial colonies were selected based on their abundance growth all of them were identified through morphological and biochemical characteristics. All the sixteen bacterial isolates were screened for its metal tolerance using nutrient agar medium incorporated with nickel metal. Based on the better growth performance, six bacterial strains were selected as potential metal tolerant organism. The selected metal tolerant bacterial strains were further characterized in the various environmental conditions such as pH (5, 7 & 9) temperature (5°C, 28°C, 37°C & 45°C) and concentration of metal ions (100ppm, 200ppm, 300ppm & 400ppm) for 5 days. The result reveals that one bacterial strain, Pseudomonas sp 1 was showed better growth in nickel metal based medium with pH 7 at 37°C temperature.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Determination of Arsenic, Chromium,Selenium and Zinc in fish samples of Bangladesh has been described and compared with the results published elsewhere.
In-Vitro Evaluation of Heavy Metal Tolerance and Biosorptive Potential of Two...semualkaira
Heavy metal contamination now a day is one of the major global
environmental concerns and industrial effluent is commonly used
for irrigation. Increasing industrial rate in the modern world is responsible for increase in concentration of heavy metals. Present
study was designed to isolate and identify some indigenous heavy
metal tolerant bacteria from textile effluents.
In-Vitro Evaluation of Heavy Metal Tolerance and Biosorptive Potential of Two...semualkaira
Heavy metal contamination now a day is one of the major global
environmental concerns and industrial effluent is commonly used
for irrigation. Increasing industrial rate in the modern world is responsible for increase in concentration of heavy metals. Present
study was designed to isolate and identify some indigenous heavy
metal tolerant bacteria from textile effluents.
Removal of Lead Ion Using Maize Cob as a BioadsorbentIJERA Editor
The intensification of industrial activity and environmental stress greatly contributes to the significant rise of
heavy metal pollution in water resources making threats on terrestrial and aquatic life. The toxicity of metal
pollution is slow and interminable, as these metal ions are non bio-degradable. The most appropriate solution for
controlling the biogeochemistry of metal contaminants is sorption technique, to produce high quality treated
effluents from polluted wastewater. Maize cob readily available was used as sorbent for the removal of lead ions
from aqueous media. Adsorption studies were performed by batch experiments as a function of process
parameters such as sorption 500ppm,2.5g, 400minutes, 400 rpm and 5 PH. Concentration, Dosage, time, rpm,
and pH. I have found that the optimized parameters are Freundlich model fits best with the experimental
equilibrium data among the three tested adsorption isotherm models. The kinetic data correlated well with the
Lagergren first order kinetic model for the adsorption studies of lead using maize cob. It was concluded that
adsorbent prepared from maize cob as to be a favorable adsorbent and easily available to remove the heavy
metal lead (II) is 95 % and can be used for the treatment of heavy metals in wastewater.
An investigation on heavy metal tolerance properties of bacteria isolated fro...AbdullaAlAsif1
The presence of high concentration of toxic heavy metals in industrial waste directly leads to contamination of receiving soil and water bodies and has deleterious impact on both human health and aquatic life. In the present study samples from textile mill effluent from different areas of Jessore city were analyzed for the identification and characterization of bacteria which shows tolerance to Copper, Mercury and Zinc. The bacterial isolates were characterized on the basis of their morphological and physiological studies including size and shape of the organisms, arrangement of the cells, presence or absence of spores, regular or irregular forms, gram reaction, cultural characteristics, IMViC test, H 2S production, nitrate reduction, deep glucose agar test etc. All the bacterial isolates belonged to 3 genera Bacillus, Enterobacter and Pseudomonas. All the gram positive isolates used in our study showed highest level of tolerance to Zn and moderate level of tolerance to Cu while gram negative isolates showed higher tolerance to Zn in comparison with Cu in nutrient broth. But all of the isolates showed almost no tolerance to Hg. So, our bacterial isolates have the probability to use in the treatment of industrial effluent containing heavy metals and thus pollution due to heavy metal can be controlled. The goal of this study was to identify heavy metal tolerant bacteria from the textile effluent. This kind of study is very significant for broader investigation to obtain data about metal tolerant bacteria considering their potential use for bioremediation and about the interactions between metals and bacteria.
Removal of heavy metals (Cr, Cd, Ni and Pb) using fresh water algae (Utricula...Innspub Net
A study was conducted to check the efficiency of different fresh water algae for removing heavy metals (Cr, Cd, Ni and Pb) from contaminated water. The three most abundant indigenous algal species namely Ulothrix tenuissima, Oscillatoria tenuis and Zygogonium ericetorum were collected from fresh water channels of Parachinar, Pakistan and brought to the laboratory of Soil and Environmental Sciences Department at the University of Agriculture, Peshawar Pakistan for proper identification. To check the efficiency for removing heavy metals artificial contaminated water was prepared and was inoculated with mix culture of above mentioned algae and incubated for 10 days. After incubation algal species were removed from water through centrifugation and was dried, digested and analyzed for heavy metals. The results showed that the concentration of all heavy metals was substantially reduced in the algal inoculated contaminated water. The analysis of algal biomass showed that considerable amount of metals and other elements were recovered in algae. Among the tested algal species, Zygogonium ericetorum showed maximum removal Ni(99.40ug) and Cr(66.84ug) from contaminated water followed by Oscillatoria tenuis with 84ug(Ni) and 64.83ug(Cr) respectively. However Oscillatoria tenuis showed maximum removal of Cd(41.00ug) than the other algal species. Similarly Zygogonium ericetorum showed maximum removal of Pb (451ug) followed by Ulothrix tenuissima where 441ug was recorded. Highest amount Cd, and Ni were recovered in Zygogonium ericetorum biomass while highest amount of Cr and Pb were recorded in the biomass of Oscillatoria tenuis. Finally it could be concluded that algae have efficiently removed heavy metals from contaminated water. Further research is needed to test other algal species for removal of heavy metal and other elements from the contaminated water.
A pilot study on effect of copper and cadmium toxicity in Tilapia Mossambicusresearchanimalsciences
Cu and Cd is trace element for most organisms including fish, but above certain limit Cu and Cd will be toxic. The present study was conducted to evaluate the toxic effect of Cu and Cd on Tilapia mossambicus via estimating the acute 96h median lethal concentration (LC50) value. A total 120 number of Tilapia mossambicus fingerlings were subjected to 12 numbers 20-L aquaria. Fish were exposed to 0.0, 2.0, 4.0, 6.0, 8.0 and 10.0mg Cu and Cd/L for 4 days. Each dose was represented by two aquaria. Fish was daily observed and dead fish were removed immediately. The data obtained were evaluated using Behrens-Karber’s Method. The 96 h LC50 value of Cu for Tilapia mossambicus was calculated to be 6.0mg Cu/L with Behrens-Karber’s Method. The 96 h LC50 value of Cd for Tilapia mossambicus was calculated to be 4.8mg Cd/L with Behrens-Karber’s Method. The behavioral changes of Tilapia mossambicus were primarily observed. It could be concluded that Tilapia mossambicus species slightly sensitive to Cu and Cd when compare both metal cadmium is more toxic than copper for the fish species.
Article Citation:
Anushia C, Sampath kumar P and Selva Prabhu A.
A Pilot Study on Effect of Copper and Cadmium Toxicity in Tilapia Mossambicus.
Journal of Research in Animal Sciences (2012) 1(1): 020-027.
Full Text:
http://janimalsciences.com/documents/AS0008.pdf
A Pilot Study on Effect of Copper and Cadmium Toxicity in Tilapia Mossambicus researchanimalsciences
Cu and Cd is trace element for most organisms including fish, but above certain limit Cu and Cd will be toxic. The present study was conducted to evaluate the
toxic effect of Cu and Cd on Tilapia mossambicus
via estimating the acute 96h median lethal concentration (LC 50 ) value. A total 120 number of
Tilapia mossambicus fingerlings were subjected to 12 numbers 20 L aquaria. Fish were exposed to 0.0, 2.0,
4.0, 6.0, 8.0 and 10.0mg Cu and Cd/L for 4 days. Each dose was represented by two aquaria. Fish was daily observed and dead fish were removed immediately. The data obtained were evaluated using Behrens - Karber’s Method. The 96 h LC 50 value of Cu for Tilapia mossambicus was calculated to be 6.0mg Cu/L with Behrens - Karber’s Method. The 96 h LC
50 value of Cd for Tilapia mossambicus was calculated to be 4.8mg Cd/L with Behrens - Karber’s Method. The behavioral changs of Tilapia mossambicus
were primarily observed. It could be concluded that Tilapia mossambicus species slightly sensitive to Cu and Cd when compare both metal
cadmium is more toxic than copper for the fish species.
The objectives of this topic are to understand, acquire, and demonstrate the concept of nanomineral synthesis, their absorption in the body, and effect on livestock productivity.
Bioaccumulation of Cadmium Heavy Metal And its Effect on the Level of Chlorop...researchinventy
Cadmium is known to inhibit the biosynthesis of chlorophyll and can disrupt the photosynthesis process. This research aimed at investigating the ability of the accumulation of cadmium heavy metals (Cd) by Thalassia hemprichii in the waters of the Ambon Island and its effect on the levels of chlorophyll and carotenoid in the leaves. Cd heavy metal analysis was carried out on samples of sea water, sediments, as well as the roots and leaves of T. hemprichii using Atomic Absorption Spectrometer (AAS). The ability of accumulation and translocation of Cd heavy metals T. hemprichii was determined by calculating the Bioconcentration Factor (BCF) and translocation factor (TF). The analysis of chlorophyll and carotenoid content used UV-Vis Spectrophotometer. The results of the research showed that the BCF value of T. hemprichii reached 141.04, while the TF value was 7.63. The BCF and TF value which was more than one indicated that T. hemprichii had the potential to be metal accumulators. The effect of the levels of Cd heavy metals in the leaves and the level of chlorophyll showed a negative correlation, but not significant. The level of Cd heavy metals in the leaves also could increase the levels of carotenoids of the leaves of T. hemprichii. These results indicate that T. hemprichii had the potential as phytoremediator in the waters of Ambon island that have been contaminated with heavy metals Cd.
2. evaluation of remediation in heavy metal tolerance and removal by comamona...Darshan Rudakiya
Comamonas acidovorans has vital role in degradation of natural as well as complex organic compounds. Comamonas acidovorans MTCC 3364 is mainly used for bioconversion of different steroids but now it is a novel approach on bioremediation. In heavy metals hexavalent chromium, mercury and lead is very toxic and carcinogenic for human health. Organism can tolerate heavy metals like hexavalent chromium, mercury, lead and aluminium with high efficiency. Removal of hexavalent chromium is major problem to textile as well as different industries. Comamonas acidovorans MTCC 3364 removed 99% of the hexavalent chromium from the medium and it can tolerate up to 600 ppm of chromium and 200 ppm of mercury in solidified medium. This organism shows high tolerance against salt i.e. it can tolerate up to 10% of salt. Chromium removal was also observed by using biosorption studies and MIC method. This bacteria increases pH during removal of chromium and makes chromium oxide which is trivalent chromium; it is a non-toxic compound. High salt tolerance, heavy metal tolerance and removal of hexavalent chromium make applicability in the treatment of waste water technology and treatment of industrial effluent which contain high amount of salt and heavy metals.
1. Name: Sayan Sarkar
Exam roll no.: M4EBT1601
Under the supervision of
Dr. Ujjal Kumar Mukhopadhyay
Chief Scientist
West Bengal Pollution Control Board
2. Arsenic
A metalloid having atomic number 33.
Commonly used in copper and lead alloys, semiconductor materials, optoelectronic materials, pesticides and
wood preservatives.
Highly toxic and disrupts the disulphide bonds in the enzymes.
Primarily affects the skin, while, prolonged exposure leads to skin and lung cancer, neurological and obstetric problems.
[Chakraborti et. al., 2002; Chakraborti et. al., 2008; Rahman et. al., 2001; Mukherjee et. al., 2003; Chakraborti et. al., 2003]
3. Arsenic occurs in four oxidation states – elemental (As0), As3+, As5+ and arsenide (As3-).
As3+ and As5+ are the most common species found in aquatic environment. [Kudo et. al. 2013]
Arsenate, containing arsenic in the form of As5+, gets easily adsorbed on the minerals. [O’Day et. al., 2004]
As3+ is more soluble and gets easily mobilized into water.
Arsenic
4. Arsenic transformation by bacteria
Reduction
o Cytosolic reduction occurs by the expression of the ars operon.
o The core genes of the ars operon are – cytosolic As5+ reductase arsC, membrane bound As3+ efflux pump arsB and
transcriptional repressor arsR.
o Another five membered ars operon (arsRDABC) is found containing additional arsA, an ATPase for arsB, and arsD, a
chaperone to the arsAB pump.
o The ars operon occurs in chromosomes or plasmids of Gram negative α-, β- and γ-Proteobacteria and Gram positive
Firmicutes and Actinobacteria.
[Escudero et. al., 2013; Cavalca et. al., 2013; Lin et. al., 2007]
5. Arsenic transformation by bacteria
Reduction
Respiratory or dissimilatory reduction occurs in various obligate or facultative anaerobes.
Bacteria obtain metabolic energy by respiration with As5+ as the terminal electron acceptor.
Respiratory As5+ reductase (Arr) is a heterodimer protein having a catalytic subunit, ArrA, and an electron transfer
subunit, ArrB.
ArrA consists of a molybdopterin centre and a [3Fe-4S] cluster.
ArrB subunit contains four [4Fe-4S] clusters.
[Saltikov and Newman, 2003; Malasarn et. al. 2004]
6. Arsenic transformation by bacteria
Oxidation
Numerous bacteria can oxidize As3+ enzymatically.
The energy and reducing power of As3+ oxidation is used in cellular growth and carbon dioxide fixation.
The enzyme As3+ oxidase is heterodimeric and consists of –
1) a small subunit with a [2Fe-2S] Rieske cluster
2) a large subunit having a molybdopterin guanosine dinucleotide at the active site and an iron binding [3Fe-4S] cluster.
The expression of the enzyme is regulated by As3+.
[Santini et. al., 2000; Oremland et. al., 2002; Ellis et. al., 2001; Lebrun et. al., 2003]
7. Arsenic transformation by bacteria
Methylation and Demethylation
Methylation is considered to be a detoxification process.
It is more common among the eukaryotes.
As5+ is reduced followed by oxidative addition of a methyl group.
For prokaryotes, the same mechanism follows except for formation of arsine.
A methyl transferase, ArsM, confer arsenic resistance and generation of trimethylarsine.
Several soil bacteria have been observed to demethylate mono- and dimethyl arsenic compounds.
[Bentley and Chesteen, 2002; Dopp et. al., 2010; Qin et. al., 2006; Yin et. al., 2011; Chen et. al., 2013]
8. Arsenic release by bacteria
o Two mechanisms for microbial release of arsenic in water are –
1) cytosolic reduction of As5+ into As3+ by certain heterotrophic and chemolithoautotrophic bacteria
2) direct respiration of As5+ present in minerals by dissimilatory As5+ reducing bacteria
[Drewniak et. al., 2008; Sultana et. al., 2012; Liao et. al., 2011; Mumford et. al., 2012]
o In case of the Bengal Delta Plain, analyses have revealed the role of metal-reducing bacteria in arsenic release.
[Sutton et. al., 2009; Sultana et. al., 2012; Akai et. al., 2004; Islam et. al., 2012]
9. Purpose of the work
Characterization and identification of bacterial strains that are aerobic and can tolerate high amount of arsenic.
To look for novel bacterial species.
To determine the role of these strains in arsenic mobilization.
To determine the potential of these strains in oxidation of arsenite.
To determine whether these strains can be utilized for bioremediation purpose.
10. Plan of work
Isolation of arsenic tolerant bacteria
Determination of growth curves
Gram’s staining
Catalase test
Determination of minimal inhibitory concentration (MIC)
Isolation of DNA
Spectrophotometric analysis of the DNA
Amplification of the 16S rRNA genes
Agarose gel electrophoresis
Soil water partitioning study
11. Isolation of arsenic tolerant bacteria
CRS2 CRS4 CMW3
Pure culture of the isolated strains in nutrient agar medium [5mM As(III)]
12. Growth curves of the isolated strains
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13
OD
Time (hours)
CRS2
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25
OD
Time (hours)
CRS4
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1 2 3 4 5 6 7 8 9 10 11
OD
Time (hours)
CMW3
Grown in nutrient broth containing 5 mM As(III)
13. Gram’s staining of the isolated strains
CRS2 CRS4
CMW3
Microscopic images of the Gram stained cells (at 100X)
17. Agarose gel electrophoresis of the amplified DNA samples
Image of the agarose gel containing the PCR products of the isolated strains viewed under UV light
19. Conclusion
• The isolated strains are moderately tolerant to high arsenic concentration.
• The strains can mobilize arsenic from soil to water.
• The arsenic mobilization by these strains are facilitated by the microbial consortia already present in the water.
• These strains are expected to oxidize arsenite into arsenate.
• The strains are indigenous, therefore, can be used in natural water or any other environment.
20. Scope of further research
• Sequencing of the amplified 16S rRNA genes to identify the bacterial species.
• Determination of arsenic transforming characteristics of these strains – both qualitative and quantitative.
• Isolation and identification of arsenic transforming genes present in these strains.
• Determination of potential of these strains in bioremediation of arsenic contaminated water and/or soil.
21. References
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