mM Of Arsenate Research Articles

Unraveling the potential of Acinetobacter calcoaceticus for arsenic resistance and plant growth promotion in contaminated lentil field

The legume crop, lentil is often found to be contaminated with arsenic (As) across the globe, and becomes a serious problem when consumed as dietary component. Bioremediation techniques are considered to be sustainable, and low cost measures to combat this problem. The current study has been aimed at identifying the As-resistant endophytic bacteria from the root nodule of lentil plants grown in As-contaminated soil, assess their capacity to tolerate As, and establish their contribution in plant growth promotion. Four As-resistant endophytic bacteria were isolated from the lentil nodules in the contaminated (17.1 and 1.54 mg kg−1 of total and available As) field (Uttar Panchponta, Nadia, West Bengal, India located at 23° 05′ N and 88° 54′ E). The results showed that among all isolates, ARGNCAR-1 exhibits the highest As resistant capacity (200.0 mM for arsenate and 21.0 mM for arsenite). Interestingly, the ARGNCAR-1(Acinetobacter calcoaceticus, KX882106) is also able to solubilize phosphate (8.59-8.6 µg mL−1 under arsenate stress and 8.0-8.1 µg mL−1 under arsenite stress) and produce significant amount of indole acetic acid (10.2-10.4 µg mL−1 under the arsenate stress and 9.4-9.5 µg mL−1 under arsenite stress). The presence of aoxB gene was detected in these four As (III) oxidizing isolates. A pot experiment was conducted with the contaminated soil and the isolated strains were inoculated. The strain ARGNCAR-1 was found to be the most efficient in reducing about 20% As from soil and 22% As from the lentil seeds and ensured significant plant yield enhancement (5.17 g plant−1) than uninoculated soil (4.54 g plant−1) mainly through their corresponding increase in pod plant−1 (110) and biomass (6.51 g plant−1). Considering the efficacy of curbing As load as well as improving plant growth, the ARGNCAR-1(Acinetobacter calcoaceticus KX882106) emerged as one of the most promising candidates in As contaminated belts.

Characterization of an antimony-resistant fungus Sarocladium kiliense ZJ-1 and its potential as an antimony bio-remediator

Antimony (Sb) is a toxic metalloid widely distributed in the natural environments. Microorganisms, especially fungi, could serve as ideal biomaterials for bioremediation of Sb-polluted soils and waters. In this study, we isolated an antimony-resistant fungus, Sarocladium kiliense ZJ-1, from a slag sample collected in Xikuangshan Sb mine in P. R. China. ZJ-1 showed an extremely high resistance to Sb, with a MIC level of > 175 mM for arsenite [Sb(Ⅲ)] and 40 mM for arsenate [Sb(V)]. Whole genomic analysis identified multiple Sb (Ⅲ)- and/or As(Ⅲ)-resistant genes on ZJ-1′s genome, which may partially explain its hyper-resistance to Sb. The potential of ZJ-1 in removing Sb from Sb(Ⅲ) or Sb(V) solutions was also quantified. The average biosorption capacity of ZJ-1 for Sb(Ⅲ) and Sb(V) is 635.14 mg/g and 149.65 mg/g, respectively, in Sb aqueous solutions with an initial concentration of 2000 mg/L (16.43 mM). Besides, almost 99% of Sb(Ⅲ) in the growing system was removed with an initial concentration of 500 mg/L (4.11 mM). Furthermore, Fourier transformation infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were used to probe the Sb adsorption mechanism on ZJ-1, and -OH, -NH2, -COOH, C-O and C-O-C were found to be the main surface functional groups of ZJ-1 cells to adsorb Sb.

Characterization of arsenic-resistant endophytic Priestia megaterium R2.5.2 isolated from ferns in an arsenic-contaminated multi-metal mine in Vietnam

Bioremediation is a biological process to remove or neutralize environmental pollutants. This study was carried out to investing at the efficacy of arsenic resistant endophytic bacteria isolated from Pteris vittata, Pityrogramma calomelanos, Blenchum orientale, and Nephrolepis exaltata, which grow in a highly arsenic (As) contamination mining site in Vietnam. Their segmented roots, stems, and leaves were homogenized separately and inoculated on LB agar plates containing 5mM As(III) and As(V). A total of 31 arsenic resistant endophytic strains were selected, in which strain R2.5.2 isolated from the root of P. calomelanos had the highest arsenic resistant capability. Strain R2.5.2 tolerated up to 320 mM and 160 mM of arsenate and arsenite, respectively. The strain developed well on a media of 0.1 5% NaCl, at 20-40ºC and pH 5 9, and actively utilized most of the sugar sources. It had a high IAA biosynthesis capacity with an average concentration of 19.14 mg/L, tolerated to 0.5-16 mM concentration of Ag+, Hg2+, Co2+, Ni2+, Cu2+, Cr4+, and reduced As(V). Based on 16s rDNA, R2.5.2 was identified as Priestia megaterium. The ars C gene coding for arsenate reductase catalyzing reduction of As(V) was successfully amplified in P. megaterium R2.5.2. The selected strain may have potential use for bioremediation practice.

Differential expression of proteins in Pseudomonas mendocina SMSKVR-3 under arsenate stress.

This study focuses on analyzing the protein expression pattern of intracellular proteins when Pseudomonas mendocina SMSKVR-3 exposed to 300 mM of arsenate to find out the proteins that are overexpressed or exclusively expressed in response to arsenate. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of protein expression at different time intervals showed the highest number of protein bands (14) that are overexpressed at 8 h of the time interval. It was also observed that treatment with at least 200 mM of As(V) is required to induce a difference in protein expression. Two-dimensional (2D)-PAGE analysis of 8-h sample exhibited 146 unique spots, 45 underexpressed, and 46 overexpressed spots in arsenate-treated sample. Based on the highest percent volume and fold change, three unique spots and one overexpressed spot were selected and analyzed by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF/TOF) mass spectrometry (MS) analysis followed by the MASCOT search. These proteins were identified as ribosome-recycling factor (20.13 kDa), polyphosphate:ADP/GDP phosphotransferase (40.88 kDa), ribonuclease P protein component (14.96 kDa) and cobalt-precorrin-5B C(1)-methyltransferase (38.43 kDa) with MASCOT score of 54, 81, 94, and 100, respectively. All of these proteins help the bacteria to overcome arsenate stress.

Characterization of arsenic resistant plant-growth promoting indigenous soil bacteria isolated from Center-East regions of India.

A total of 45 morphologically distinct arsenic (As)-resistant bacterial strains were isolated from the soils of different regions of Chhattisgarh, India. The minimum inhibitory concentration (MIC) values of these isolates varied widely in the range of 100-500 mM for arsenate [As(V)] and 15-30 mM for arsenite [As(III)]. Out of forty-five, three isolates viz; ARP3, ARRP3, and ADT5 also revealed plant growth-promoting properties, including phosphate solubilization and production of siderophores, indoleacetic acid, ammonia, and exopolysaccharide. Besides all these, the strains not only exhibited significant growth in the presence of As(V)/As(III) but also displayed higher efficiency (87%-94%) of As removal from the growth medium followed by intracellular accumulation (17-19 mg As/g). Hydride generation atomic absorption spectroscopic (HG-AAS) analysis revealed the intracellular accumulation of As, and the structural changes that tookplace in these isolates werefurther confirmed by microscopic studies. The 16 S rRNA and phylogenetic analyses unveiled that the isolates ARP3, ARRP3, and ADT5 belonged to genera Pseudomonas, Exiguobaterium, and Microbacterium, respectively. The conducted study suggested that such beneficial bacterial strains could be conveniently exploited at a commercial level for enhancing plant growth in As-contaminated agricultural fields, thereby improved productivity and enhanced bioremediation of soil having alarming strength of As.

The Effect of UV Light on Increasing the Arsenate Resistance of Acidithiobacillus Ferrooxidans

Introduction: Mutations are the most popular way to increase the efficiency of mineral waste bioleaching. Acidithiobacillus ferrooxidans are used as an important microorganism in biohydrometallurgy. Arsenate is one of the toxic elements in mines, which reduces the efficiency of A. ferrooxidans leaching. The purpose of this research was to increase the resistance of A. ferrooxidans to high concentrations of arsenate. Materials and Methods: This research was an analytical – descriptive study. The studied population was isolated A. ferrooxidans bacterium from the Sarcheshmeh copper mine in Kerman. The highest tolerable concentration of arsenate was determined by successive cultures of this bacterium at increasing concentrations of arsenate. The bacteria were exposed to UV radiation at different times and then cultured in higher concentrations of arsenate. Results: The results showed that the wild strain was able to grow in the medium containing 20 mM of arsenate. With adaptation, this bacterial strain could grow in medium containing increasing concentrations (40, 60, 80, 100, 120, and 140 mM) of arsenate. When the bacterium was exposed to UV ray for 60 minutes, it was able to grow at a concentration of 120 mM of arsenate. Conclusion: The results indicated a very good effect of UV ray on increasing the arsenate resistance of A. ferrooxidans. It is suggested that this modified strain can be used in real environments for bioleaching.

The whole genome insight on condition-specific redox activity and arsenopyrite interaction promoting As-mobilization by strain Lysinibacillus sp. B2A1.

A gram-positive spore former, Lysinibacillus sp. B2A1 was isolated from a high arsenic containing groundwater of Beimen2A well, Chianan Plain area, Southwestern Taiwan. Noteworthy, in the subsurface-mimicking anoxic incubation with a Na-lactate amendment system, this isolate could interact with arsenic-source mineral arsenopyrite and enhance arsenic mobilization. Further, the isolate showed elevated levels of arsenic resistance, 200 mM and 7.5 mM for arsenate and arsenite, respectively. Lysinibacillus sp. B2A1 demonstrated condition-specific redox activities including salient oxic oxidation of arsenite and anoxic reduction of arsenate. The elevated rate of As(III) oxidation (Vmax = 0.13 μM min-1 per 106 cells, Km = 15.3 μM) under oxic conditions was potent. Correlating with stout persistence in an arsenic-rich niche, remarkably, the lesser toxic effects of arsenic ions on bacterial sporulation frequency and germination highlight this strain's ability to thrive under catastrophic conditions. Moreover, the whole genome analysis elucidated diverse metal redox/resistance genes that included a potential arsenite S-adenosylmethyltransferase capable of mitigating arsenite toxicity. Owing to its arsenic resistance, conditional redox activities and ability to interact with arsenic minerals leading to arsenic mobilization, the presence of such spore-forming strains could be a decisive indication towards arsenic mobilization in subsurface aquifers having a high concentration of soluble arsenic or its source minerals.

Characterization of arsenite-oxidizing bacteria to decipher their role in arsenic bioremediation

High arsenic groundwater contamination causes serious health risks in many developing countries, particularly in India and Bangladesh. The arsenic fluxes in aquifers are primarily controlled by bacterial populations through biogeochemical cycle. In this present study, two gram-positive rod-shaped bacteria were isolated from shallow aquifers of Bhojpur district in Bihar during the early winter season, able to withstand arsenite (As3+) concentration upto 70 mM and 1000 mM of arsenate (As5+) concentration. They showed high resistance to heavy metals up to 30 mM and utilized some complex sugars along with different carbon sources. Growth at wide range of temperature, pH and salinity were observed. Both these isolates showed high efficiency in converting As3+ into less toxic concentrations of As5+ respectively from arsenic enriched culture media. Along with superior arsenic transformation and arsenic resistance abilities, the isolates showed a wide variety of metabolic capacity in terms of utilizing a variety of carbon sources under aerobic conditions, respectively. This study reports the potential As3+-oxidizing bacteria that can play an important role in subsurface arsenic transformation that will aid in designing future bioremediation strategy for the arsenic affected areas.

Characterization of arsenite tolerant Halomonas sp. Alang-4, originated from heavy metal polluted shore of Gulf of Cambay

ABSTRACTArsenite [As(III)]-oxidizing bacteria were isolated from heavy metal contaminated shore of Gulf of Cambay at Alang, India. The most efficient bacterial strain Alang-4 could tolerate up to 15 mM arsenite [As(III)] and 200 mM of arsenate [As(V)]. Its 16S rRNA gene sequence was 99% identical to the 16S rRNA genes of genus Halomonas (Accession no. HQ659187). Arsenite oxidase enzyme localized on membrane helped in conversion of As(III) to As(V). Arsenite transporter genes (arsB, acr3(1) and acr3(2)) assisted in extrusion of arsenite from Halomonas sp. Alang-4. Generation of ROS in response to arsenite stress was alleviated by higher activities of catalase, ascorbate peroxidase, superoxide dismutase and glutathione S-transferase enzymes. Down-regulation in the specific activities of nearly all dehydrogenases of carbon assimilatory pathway viz., glucose-6-phosphate, pyruvate, α-ketoglutarate, isocitrate and malate dehydrogenases, was observed in presence of As(III), whereas, the specific activities of phosphoenol pyruvate carboxylase, pyruvate carboxylase and isocitrate lyase enzymes were found to increase two times in As(III) treated cells. The results suggest that in addition to efficient ars operon, alternative pathways of carbon utilization exist in the marine bacterium Halomonas sp. Alang-4 to overcome the toxic effects of arsenite on its dehydrogenase enzymes.

Isolation and Molecular Characterization of Arsenite-Tolerant Alishewanella sp. GIDC-5 Originated from Industrial Effluents

An As-hypertolerant Alishewanella sp. GIDC-5 (Accession no. HQ659190) was isolated from an effluent treatment plant of the industrial area near Sachin, Gujarat (India). In vitro studies revealed that GIDC-5 can tolerate 18 mM of arsenite [As(III)] and 220 mM of arsenate [As(V)]. PCR analysis confirmed the presence of arsenite transporters [arsB and ACR3(1)] and arsenite oxidase gene [aioB]. Specific activities of arsenite oxidase and arsenate reductase, located on membrane and cytoplasmic fractions respectively, increased in dose dependent manner with arsenite concentration. Also, specific activities of antioxidant enzymes viz., catalase, ascorbate peroxidase, superoxide dismutase and glutathione S-transferase increased in presence of arsenite. Increased exposure to arsenite changes enzyme activities of the glycolysis, Krebs and glyoxylate branches dramatically. These results reveal that along with ars operon, metabolic adaptation and antioxidant activities participate in As(III) tolerance in Alishewanella sp. GIDC-5.

Arsenic accumulation by Pseudomonas stutzeri and its response to some thiol chelators

The aim of this study is to examine arsenic accumulation by Pseudomonas stutzeri and its response to some thiol chelators, DMPS and MiADMSA. Determination of arsenic accumulation by Pseudomonas sp. was carried out using an atomic absorption spectrophotometer, a TEM and an EDAX. Arsenate reductase enzyme assay was carried out from a cell-free extract of Pseudomonas sp. The effect of chelating agents on arsenite accumulation was analyzed. Total cellular proteins were analyzed using 1-D SDS-PAGE. Pseudomonas sp. exhibited a maximum accumulation of 4 mg As g(-1) (dry weight). TEM and EDAX analysis showed the presence of As-containing electron-dense particles inside the cells. Data on arsenate reductase enzyme kinetics yielded a K (m) of 0.40 mM for arsenate and a V (max) of 5,952 mumol arsenate reduced per minute per milligram of protein. The chelating agents MiADMSA and DMPS were found to reduce the arsenic accumulation by 60 and 35%, respectively, whereas the presence of both chelating agents in medium containing cells pretreated with arsenite reduced it by up to 90%. The total protein profile of the cellular extract, obtained by 1-D SDS-PAGE, indicated five upregulated proteins, and three of these proteins exhibited differential expression when the cells were grown with MiADMSA and DMPS. This study shows a new approach towards arsenic detoxification. A combination treatment with MiADMSA and DMPS may be useful for removing intracellular arsenic. The proteins that were found to be induced in this study may play an important role in the extrusion of arsenic from the cells, and this requires further characterization.

Bacteria, hypertolerant to arsenic in the rocks of an ancient gold mine, and their potential role in dissemination of arsenic pollution

The aim of the present study was to find out if bacteria present in ancient gold mine could transform immobilized arsenic into its mobile form and increase its dissemination in the environment. Twenty-two arsenic-hypertolerant cultivable bacterial strains were isolated. No chemolithoautotrophs, which could use arsenite as an electron donor as well as arsenate as an electron acceptor, were identified. Five isolates exhibited hypertolerance to arsenic: up to 500mM of arsenate. A correlation between the presence of siderophores and high resistance to arsenic was found. The results of this study show that detoxification processes based on arsenate reductase activity might be significant in dissemination of arsenic pollution. It was concluded that the activity of the described heterotrophic bacteria contributes to the mobilization of arsenic in the more toxic As(III) form and a new mechanism of arsenic mobilization from a scorodite was proposed.

Removal of arsenate, chromate and ferricyanide by cationic surfactant modified powdered activated carbon

In this study, surfactant-modified powdered activated carbon (PAC) was used to remove anionic contaminants from water. The conventional modification method of PAC with surfactants produced large quantity of unbound surfactant in aqueous phase (3.0–3.5 mM). However, the revised modification method — filtration followed by centrifugation — released negligible amount of residual surfactant (<0.01 mM). Adsorption characteristics were investigated with arsenate (H 2AsO 4 −), chromate (CrO 4 2−) and ferricyanide (Fe(CN) 6 3−). The adsorption isotherm followed Langmuir model, and it suggested that the anions bind on the monolayer of the modified PAC by the electrostatic attraction. The order of maximum adsorbed amount was chromate (0.234 mmol/g) > arsenate (0.087 mmol/g) ≈ ferricyanide (0.085 mmol/g). On the other hand, the order changed to ferricyanide > chromate > arsenate in multi-contaminant system. Anions competed with each other for limited binding sites in the multicontaminant system, hence the order of maximum adsorbed amount followed the valence of each anion. With 2 g/L of modified PAC, it was possible to treat 0.001 mM of arsenate, 0.5 mM of chromate and 0.2 mM of ferricyanide completely.

Social bacteria and asocial eukaryotes

The end of 2007 brought us draft genome sequences of two eukaryotic microorganisms, Babesia bovis and Malassezia globosa, as well as complete genomes of the ammonia-oxidizing archaeal chemoautotroph Nitrosopumilus maritimus, and several environmental bacteria (Table 1). In terms of genome size, this list covers both sides of the spectrum: the 245 kb genome of an obligate insect symbiont Sulcia muelleri is the second smallest microbial genome sequenced so far, whereas the 13 033 kb chromosome of the social myxobacterium Sorangium cellulosum breaks the record as the largest bacterial genome – and the largest DNA molecule in the prokaryotic world.

Hyperaccumulation of arsenic by callus, sporophytes and gametophytes of Pteris vittata cultured in vitro

The callus of Pteris vittata was induced from gametophytes generated from spores in vitro, and grew rapidly with periodical medium change. Arsenic tolerance and accumulation of P. vittata callus were compared with those of Arabidopsis thaliana callus. Cell death was not detected in P. vittata callus even at arsenate concentrations up to 2 mM; however, A. thaliana callus died at low (0.2 mM) arsenate concentrations. Meanwhile, P. vittata callus accumulated almost three times more As than A. thaliana callus when exposed to 0.2 mM arsenate. About 60% of the total As was removed when 7.5 g of P. vittata callus was cultured on 150 ml of half-strength MS liquid medium containing 450 microg As for 2 days. Furthermore, P. vittata callus, sporophytes, and gametophytes all grew well under 1 mM of arsenate and accumulated 1,250; 1,150 and 2,180 mg kg(-1 )dry weight As when grown on 2 mM arsenate for 15 or 30 days. The characteristics of non-differentiated cells, large biomass, ease of culture, good synchronization, and excellent As sequestering, make the callus of P. vittata a new ideal system to study the mechanisms of As hyperaccumulation and phytoremediation in As-contaminated groundwater.

Arsenic resistance in Pteris vittata L.: identification of a cytosolic triosephosphate isomerase based on cDNA expression cloning in Escherichia coli

Arsenic hyperaccumulator Pteris vittata L. (Chinese brake fern) grows well in arsenic-contaminated media, with an extraordinary ability to tolerate high levels of arsenic. An expression cloning strategy was employed to identify cDNAs for the genes involved in arsenic resistance in P. vittata. Excised plasmids from the cDNA library of P. vittata fronds were introduced into Escherichia coli XL-1 Blue and plated on medium containing 4 mM of arsenate, a common form of arsenic in the environment. The deduced amino acid sequence of an arsenate-resistant clone, PV4-8, had cDNA highly homologous to plant cytosolic triosephosphate isomerases (cTPI). Cell-free extracts of PV4-8 had 3-fold higher level of triosephosphate isomerase (TPI) specific activities than that found in E. coli XL-1 Blue and had a 42 kD fusion protein immunoreactive to polyclonal antibodies raised against recombinant Solanum chacoense cTPI. The PV4-8 cDNA complemented a TPI-deficient E. coli mutant. PV4-8 expression improved arsenate resistance in E. coli WC3110, a strain deficient in arsenate reductase but not in AW3110 deficient for the whole ars operon. This is consistent with the hypothesis that PV4-8 TPI increased arsenate resistance in E. coli by directly or indirectly functioning as an arsenate reductase. When E. coli tpi gene was expressed in the same vector, bacterial arsenate resistance was not altered, indicating that arsenate tolerance was specific to P. vittata TPI. Paradoxically, P. vittata TPI activity was not more resistant to inhibition by arsenate in vitro than its bacterial counterpart suggesting that arsenate resistance of conventional TPI reaction was not the basis for the cellular arsenate resistance. P. vittata TPI activity was inhibited by incubation with reduced glutathione while bacterial TPI was unaffected. Consistent with cTPI's role in arsenate reduction, bacterial cells expressing fern TPI had significantly greater per cent of cellular arsenic as arsenite compared to cells expressing E. coli TPI. Excised frond tissue infiltrated with arsenate reduced arsenate significantly more under light than dark. This research highlights a novel role for P. vittata cTPI in arsenate reduction.

Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator.

Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.

Some properties of glutamate dehydrogenase, glutamine synthetase and glutamate synthase from Corynebacterium callunae.

Characteristics of the three major ammonia assimilatory enzymes, glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutamate synthase (GO-GAT) in Corynebacterium callunae (NCIB 10338) were examined. The GDH of C. callunae specifically required NADPH and NADP+ as coenzymes in the amination and deamination reactions, respectively. This enzyme showed a marked specificity for alpha-ketoglutarate and glutamate as substrates. The optimum pH was 7.2 for NADPH-GDH activity (amination) and 9.0 for NADP(+)-GDH activity (deamination). The results showed that NADPH-GDH and NADP(+)-GDH activities were controlled primarily by product inhibition and that the feedback effectors alanine and valine played a minor role in the control of NADPH-GDH activity. The transferase activity of GS was dependent on Mn+2 while the biosynthetic activity of the enzyme was dependent on Mg2+ as essential activators. The pH optima for transferase and biosynthetic activities were 8.0 and 7.0, respectively. In the transfer reaction, the Km values were 15.2 mM for glutamine, 1.46 mM for hydroxylamine, 3.5 x 10(-3) mM for ADP and 1.03 mM for arsenate. Feedback inhibition by alanine, glycine and serine was also found to play an important role in controlling GS activity. In addition, the enzyme activity was sensitive to ATP. The transferase activity of the enzyme was responsive to ionic strength as well as the specific monovalent cation present. GOGAT of C. callunae utilized either NADPH or NADH as coenzymes, although the latter was less effective. The enzyme specifically required alpha-ketoglutarate and glutamine as substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of lead, cadmium, arsenate, and fluoride ions on the growth and fine structure of Sphagnum nemoreum in aseptic culture

The growth of Sphagnum nemoreum Scop, and the fine structure of its leaf cells were studied in aseptic cultures to which were added lead, cadmium, arsenate, and fluoride (0.001, 0.01, 0.1, and 1 mM solutions). The highest concentration having no or almost no effect on the dry weight was 0.1 mM for lead, 0.01 mM for fluoride and cadmium, and 0.001 mM for arsenate. The 1 mM solution of Na2HAsO4 and 0.1 mM solution of CdSO4 were toxic and the inocules died rapidly. The 1 mM solutions of KF and Pb(NO3)2 were growth-retarding. The chloroplasts tended to accumulate starch when arsenate (0.1 mM) was added to the medium. Fluoride promoted the development of plastoglobuli, and lead (0.1 mM) promoted lipid accumulation in the cytoplasm. High concentrations of arsenate and fluoride inhibited the differentiation of hyaline cells. The physiological and ecological effects of these substances have been discussed with special reference to the problem of pollution.