Impairment of cobalt-induced riboflavin biosynthesis in aDebaryomyces hanseniimutant

2007 ◽  
Vol 53 (11) ◽  
pp. 1272-1277 ◽  
Author(s):  
Jasmine M. Seda-Miró ◽  
Nancy Arroyo-González ◽  
Ana Pérez-Matos ◽  
Nadathur S. Govind
Keyword(s):  
Heavy Metals ◽  
Metal Tolerance ◽  
Debaryomyces Hansenii ◽  
Chemical Mutagenesis ◽  
Lag Phase ◽  
Riboflavin Biosynthesis ◽  
Wild Type ◽  
Ura3 Gene ◽  
Type D ◽  
Metal Sensitivity

Flavinogenic yeasts such as Debaryomyces hansenii overproduce riboflavin (RF) in the presence of heavy metals. Growth and RF production were compared between wild-type D. hansenii and a RF production-impaired metal-tolerant ura3 mutant in the presence of sublethal cobalt(II) concentrations. Debaryomyces hansenii (wild type) exhibits an extended lag phase with an increase in RF synthesis. Supplementation of exogenous uracil shortened the lag phase at the highest concentration of cobalt(II) used, suggesting that uracil has a possible role in metal acclimation. The D. hansenii ura3 mutant isolated by chemical mutagenesis exhibited a higher level of metal tolerance, no extended lag phase, and no marked increase in RF synthesis. Transformation of the mutant with the URA3 gene isolated from Saccharyomyces cerevisiae or D. hansenii did not restore wild-type characteristics, suggesting a second mutation that impairs RF oversynthesis. Our results demonstrate that growth, metal sensitivity, and RF biosynthesis are linked.

Overcoming the Bacteriostatic Effects of Heavy Metals on A. thiooxidans Direct Bioleaching of Saprolitic Ni Laterite Ores

2015 ◽  
Vol 1130 ◽  
pp. 263-267 ◽  
Author(s):  
Hee Chan Jang ◽  
Marjorie Valix
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Metal Tolerance ◽  
Heavy Metal Tolerance ◽  
Heavy Metal Stress ◽  
Lag Phase ◽  
Tolerance Index ◽  
Acid Generation ◽  
Laterite Ores ◽  
Laterite Ore

In this study, the adaptation of A. thiooxidans to heavy metals leached from saprolitic Ni laterite ores was performed by gradual acclimatisation. The bacteria was cultivated in heavy metals (Ni, Co, Fe, Mg, Cr and Mn) with total concentrations of 2400 to 24000 ppm equivalent to total dissolution of 1 to 10% (w/v) pulp densities of the saprolitic Ni laterite ore. Adaptation evolution mapped from its tolerance index was found to be dependent on metal concentration, acid generation, and period of adaptation. Bio-stimulation of cell growth and acid production was promoted by heavy metal stress on the bacteria. Pre-established heavy metal tolerance of the bacteria improved the leaching rate in its early phase; 20% and 7% increase in Ni and Co metal recoveries were observed in using adapted bacteria. However heavy metal tolerance was also achieved by the bacteria during the leaching process, albeit delayed by a lag phase. These results confirm the robust nature and suitability of A. thiooxidans in direct biomining of Ni ores.

scholarly journals Actin-dependent regulation of the cardiac Na+/Ca2+ exchanger

2006 ◽  
Vol 290 (3) ◽  
pp. C691-C701 ◽  
Author(s):  
Madalina Condrescu ◽  
John P. Reeves
Keyword(s):  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Cytochalasin D ◽  
Lag Phase ◽  
Cell Contact ◽  
Wild Type ◽  
Filamentous Actin ◽  
Surface Distribution ◽  
Reverse Mode ◽  
Hydrophilic Domain

In the present study, the bovine cardiac Na+/Ca2+ exchanger (NCX1.1) was expressed in Chinese hamster ovary cells. The surface distribution of the exchanger protein, externally tagged with the hemagglutinin (HA) epitope, was associated with underlying actin filaments in regions of cell-to-cell contact and also along stress fibers. After we treated cells with cytochalasin D, NCX1.1 protein colocalized with patches of fragmented filamentous actin (F-actin). In contrast, an HA-tagged deletion mutant of NCX1.1 that was missing much of the exchanger's central hydrophilic domain Δ(241–680) did not associate with F-actin. In cells expressing the wild-type exchanger, cytochalasin D inhibited allosteric Ca2+ activation of NCX activity as shown by prolongation of the lag phase of low Ca2+ uptake after initiation of the reverse (i.e., Ca2+ influx) mode of NCX activity. Other agents that perturbed F-actin structure (methyl-β-cyclodextrin, latrunculin B, and jasplakinolide) also increased the duration of the lag phase. In contrast, when reverse-mode activity was initiated after allosteric Ca2+ activation, both cytochalasin D and methyl-β-cyclodextrin (Me-β-CD) stimulated NCX activity by ∼70%. The activity of the Δ(241–680) mutant, which does not require allosteric Ca2+ activation, was also stimulated by cytochalasin D and Me-β-CD. The increased activity after these treatments appeared to reflect an increased amount of exchanger protein at the cell surface. We conclude that wild-type NCX1.1 associates with the F-actin cytoskeleton, probably through interactions involving the exchanger's central hydrophilic domain, and that this association interferes with allosteric Ca2+ activation.

scholarly journals CodY Is a Global Regulator of Virulence-Associated Properties for Clostridium perfringens Type D Strain CN3718

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
Jihong Li ◽  
Menglin Ma ◽  
Mahfuzur R. Sarker ◽  
Bruce A. McClane
Keyword(s):  
Clostridium Perfringens ◽  
Null Mutant ◽  
Intestinal Infection ◽  
Wild Type ◽  
Global Regulator ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Type D ◽  
Epsilon Toxin ◽  
Virulence Properties

ABSTRACT CodY is known to regulate various virulence properties in several Gram-positive bacteria but has not yet been studied in the important histotoxic and intestinal pathogen Clostridium perfringens. The present study prepared an isogenic codY-null mutant in C. perfringens type D strain CN3718 by insertional mutagenesis using the Targetron system. Western blot analysis indicated that, relative to wild-type CN3718 or a complementing strain, this isogenic codY mutant produces reduced levels of epsilon toxin (ETX). Using supernatants from cultures of the wild-type, codY-null mutant, and complementing strains, CodY regulation of ETX production was shown to have cytotoxic consequences for MDCK cells. The CodY regulatory effect on ETX production was specific, since the codY-null mutant still made wild-type levels of alpha-toxin and perfringolysin O. Sialidase activity measurements and sialidase Western blot analysis of supernatants from CN3718 and its isogenic derivatives showed that CodY represses overall exosialidase activity due to a reduced presence of NanH in culture supernatants. Inactivation of the codY gene significantly decreased the adherence of CN3718 vegetative cells or spores to host Caco-2 cells. Finally, the codY mutant showed increased spore formation under vegetative growth conditions, although germination of these spores was impaired. Overall, these results identify CodY as a global regulator of many C. perfringens virulence-associated properties. Furthermore, they establish that, via CodY, CN3718 coordinately regulates many virulence-associated properties likely needed for intestinal infection. IMPORTANCE Clostridium perfringens is a major human and livestock pathogen because it produces many potent toxins. C. perfringens type D strains cause intestinal infections by producing toxins, especially epsilon toxin (ETX). Previous studies identified CodY as a regulator of certain virulence properties in other Gram-positive bacteria. Our study now demonstrates that CodY is a global regulator of virulence-associated properties for type D strain CN3718. It promotes production of ETX, attachment of CN3718 vegetative cells or spores to host enterocyte-like Caco-2 cells, and spore germination; the last two effects may assist intestinal colonization. In contrast, CodY represses sporulation. These results provide the first evidence that CodY can function as a global regulator of C. perfringens virulence-associated properties and that this strain coordinately regulates its virulence-associated properties using CodY to increase ETX production, host cell attachment, and spore germination but to repress sporulation, as would be optimal during type D intestinal infection.

scholarly journals A novel positive selection for identifying cold-sensitive myosin II mutants in Dictyostelium.

Genetics ◽  
1995 ◽  
Vol 140 (2) ◽  
pp. 505-515 ◽  
Author(s):  
B Patterson ◽  
J A Spudich
Keyword(s):  
Positive Selection ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Time Scale ◽  
Myosin Ii ◽  
Rapid Onset ◽  
Chemical Mutagenesis ◽  
Wild Type ◽  
Cold Sensitive ◽  
Selection For

Abstract We developed a positive selection for myosin heavy chain mutants in Dictyostelium. This selection is based on the fact that brief exposure to azide causes wild-type cells to release from the substrate, whereas myosin null cells remain adherent. This procedure assays myosin function on a time scale of minutes and has therefore allowed us to select rapid-onset cold-sensitive mutants after random chemical mutagenesis of Dictyostelium cells. We developed a rapid technique for determining which mutations lie in sequences of the myosin gene that encode the head (motor) domain and localized 27 of 34 mutants to this domain. We recovered the appropriate sequences from five of the mutants and demonstrated that they retain their cold-sensitive properties when expressed from extrachromosomal plasmids.

scholarly journals In vivo and in vitro studies on heavy metal tolerance in Sesbania grandiflora L

2009 ◽  
Vol 3 (2) ◽  
pp. 48-64
Author(s):  
Kadhim M. Ibrahim ◽  
Shaimaa A. Yousir
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Metal Tolerance ◽  
Heavy Metal Tolerance ◽  
Heavy Metal Concentration ◽  
Callus Cultures ◽  
Metal Levels ◽  
Whole Plants

Several experiments were carried out to study heavy metal tolerance in tissue cultures or whole plants of S. grandiflora., Callus was induced and maintained on modified Murashige and Skoog, 1962 medium (MS) supplemented with (0.5)mg/l benzyl adenine and (2)mg/l 2,4-phenoxy acetic acid . Heavy metals (Cd, Co, Cu, Cr or Zn) were added to the culture medium at different concentrations as contamination agents. In order to asses the effect of these heavy metals on seed germination; seeds were sown in soil contaminated with different concentrations of heavy metals for 3 weeks. Atomic Absorption Spectrophotometer was used for analysis of samples taken from whole plants and callus cultures. Results showed that callus fresh weight decreased with increasing heavy metal concentration in cultural medium. Germination percentages and plant heights increased over time. However, a reduction occurred in these parameters with increasing heavy metal levels. Percentages of metals accumulated in calli were (0.001, 0.011, 0.012 and 0.013%) at (0.0, 0.05, 0.075 and 0.1)mg/l Cd respectively; (0.001, 0.008, 0.016 and 0.006%) at (0.0, 0.1, 0.25 and 0.5)mg/l Co respectively; (0.001, 0.020, 0.034 and 0.015%) at (0.0, 0.075, 0.2 and 0.5)mg/l Cu respectively; (0.001, 0.013, 0.012 and 0.010%) at (0.0, 0.25, 0.4 and 0.5)mg/l Cr respectively and (0.027, 0.051, 0.059 and 0.056%) at (0.0 , 0.75, 1.0 and 1.5)mg/l Zn respectively. Percentages of metals accumulated in whole plants were (0.08, 0.55, 1.11, 0.83 and 0.44%) at (0.0, 1.0, 2.0, 3.0 and 4.0)mg/Kg soil Cd respectively; (0.11, 0.22, 0.55, 0.47 and 0.44%) at (0.0, 15.0, 30.0 45.0 and 60.0)mg/Kg soil Co respectively; (0.01, 0.10, 0.57, 0.58 and 0.72%) at (0.0, 25.0, 50.0, 75.0 and 100.0)mg/Kg soil Cu respectively. (0.08, 0.80, 1.28, 1.31 and 0.88%) at (0.0, 25.0, 50.0, 75.0 and 100.0)mg/Kg soil Cr respectively and (0.06, 1.11, 1.20, 1.83 and 2.22%) at (0.0, 100.0, 200.0, 300.0 and 400.0)mg/Kg soil Zn respectively.

scholarly journals Increased metal tolerance and bioaccumulation of zinc and cadmium in Chlamydomonas reinhardtii expressing a AtHMA4 C-terminal domain protein

2020 ◽  
Author(s):  
Aniefon Ibuot ◽  
Rachel E. Webster ◽  
Lorraine E. Williams ◽  
Jon K. Pittman
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Metal Binding ◽  
Metal Tolerance ◽  
Alginate Beads ◽  
Full Length ◽  
Wild Type ◽  
Microalgal Biomass ◽  
Terminal Domain ◽  
Metal Biosorption ◽  
Transgenic Cells

AbstractThe use of microalgal biomass for metal pollutant bioremediation might be improved by genetic engineering to modify the selectivity or capacity of metal biosorption. A plant cadmium (Cd) and zinc (Zn) transporter (AtHMA4) was used as a transgene to increase the ability of Chlamydomonas reinhardtii to tolerate 0.2 mM Cd and 0.3 mM Zn exposure. The transgenic cells showed increased accumulation and internalisation of both metals compared to wild type. AtHMA4 was expressed either as the full-length protein or just the C-terminal tail, which is known to have metal binding sites. Similar Cd and Zn tolerance and accumulation was observed with expression of either the full-length protein or C-terminal domain, suggesting that enhanced metal tolerance was mainly due to increased metal binding rather than metal transport. The effectiveness of the transgenic cells was further examined by immobilisation in calcium alginate to generate microalgal beads that could be added to a metal contaminated solution. Immobilisation maintained metal tolerance, while AtHMA4-expressing cells in alginate showed a concentration-dependent increase in metal biosorption that was significantly greater than alginate beads composed of wild type cells. This demonstrates that expressing AtHMA4 full-length or C-terminus has great potential as a strategy for bioremediation using microalgal biomass.

scholarly journals Heavy Metal Tolerance Bacillus spp Isolated From Crude Oil Polluted Soil

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Muibat Fashola
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Crude Oil ◽  
Metal Tolerance ◽  
Heavy Metal Tolerance ◽  
Polluted Soil ◽  
Diffusion Method ◽  
Bacillus Species ◽  
Antibiotics Resistance ◽  
Bacillus Spp

Introduction: Indiscriminate dumping of spent oils enriched with heavy metals has led to increase in heavy metals load in the soil. Heavy metals exert toxic effects on biodegradation of organic pollutant in cocontaminated soil and there is need to find suitable strategies for their removal. Aim: The aim of this study was to assess the heavy metals resistance capability of indigenous Bacillus species in hydrocarbon polluted soil to nickel (Ni), Cadmium (Cd), Lead (Pb) and Chromium (Cr). Materials and Methods: Heavy metal tolerant bacteria were isolated from hydrocarbon polluted soil using Luria-Berthani agar supplemented with the respective metals and spread plate techniques. The isolates were putatively identified on the basis of their colonial morphology and biochemical characteristics and their antibiotics susceptibility pattern were evaluated using disc diffusion method. Results: The maximum tolerable concentration (MTC) of the four heavy metals to the selected isolates was 2 mM. Four bacteria isolates able to withstand the MTC were putatively identified as Bacillus subtilis, Bacillus megaterium, Bacillus laterosporus and Bacillus polymyxa. Out of the four Bacillus species, only B. laterosporus did not show multiple tolerance to the tested antibiotics which show that there is correlation between heavy metal tolerance and antibiotics resistance by the isolates. Conclusion: Multiple heavy metal tolerance Bacillus spp. were isolated from crude oil polluted soil. These bacteria could be suitable agents for bioaugmentation of hydrocarbon polluted soil co-contaminated with heavy metals.

Isolation and characterization of heavy metal tolerant Gram-positive bacteria with bioremedial properties from municipal waste rich soil of Kestopur canal (Kolkata), West Bengal, India

Biologia ◽  
2012 ◽  
Vol 67 (5) ◽  
Author(s):  
Kamala Gupta ◽  
Chitrita Chatterjee ◽  
Bhaskar Gupta
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Metal Tolerance ◽  
Environmental Pollutants ◽  
Heavy Metal Tolerance ◽  
Antibiotic Sensitivity ◽  
Bacterial Strains ◽  
High Concentration ◽  
Isolation And Characterization ◽  
Bacillus Weihenstephanensis

AbstractThe present study was conducted to determine the culturable bacterial profile from Kestopur canal (Kolkata, India) and analyze their heavy metal tolerance. In addition to daily sewage including solid and soluble wastes, a considerable load of toxic metals are released into this water body from industries, tanneries and agriculture, household as well as health sectors. Screening out microbes from such an environment was done keeping in mind their multifunctional application especially for bioremediation. Heavy metals are major environmental pollutants when present in high concentration in soil and show potential toxic effects on growth and development in plants and animals. Some edible herbs growing in the canal vicinity, and consumed by people, were found to harbour these heavy metals at sub-toxic levels. The bioconcentration factor of these plants being <1 indicates that they probably only absorb but not accumulate heavy metals. All the thirteen Grampositive bacteria isolated from these plants rhizosphere were found to tolerate high concentration of heavy metals like Co, Ni, Pb, Cr, Fe. Phylogenetic analysis of their 16S rDNA genes revealed that they belonged to one main taxonomic group — the Firmicutes. Seven of them were found to be novel with 92–95% sequence homology with known bacterial strains. Further microbiological analyses show that the alkaliphilic Bacillus weihenstephanensis strain IA1 and Exiguobacterium aestuarii strain CE1, with selective antibiotic sensitivity along with high Ni2+ and Cr6+ removal capabilities, respectively, can be prospective candidates for bioremediation.

scholarly journals Chemical Mutagenesis and Fluorescence-Based High-Throughput Screening for Enhanced Accumulation of Carotenoids in a Model Marine Diatom Phaeodactylum tricornutum

Marine Drugs ◽  
2018 ◽  
Vol 16 (8) ◽  
pp. 272 ◽  
Author(s):  
Zhiqian Yi ◽  
Yixi Su ◽  
Maonian Xu ◽  
Andreas Bergmann ◽  
Saevar Ingthorsson ◽  
...  
Keyword(s):  
High Throughput ◽  
Metabolic Pathways ◽  
Phaeodactylum Tricornutum ◽  
Mass Spectrometry Data ◽  
Marine Diatom ◽  
Chemical Mutagenesis ◽  
Carotenoid Content ◽  
Enzymatic Reactions ◽  
Wild Type ◽  
A Genome

Diatoms are a major group of unicellular algae that are rich in lipids and carotenoids. However, sustained research efforts are needed to improve the strain performance for high product yields towards commercialization. In this study, we generated a number of mutants of the model diatom Phaeodactylum tricornutum, a cosmopolitan species that has also been found in Nordic region, using the chemical mutagens ethyl methanesulfonate (EMS) and N-methyl-N′-nitro-N-nitrosoguanidine (NTG). We found that both chlorophyll a and neutral lipids had a significant correlation with carotenoid content and these correlations were better during exponential growth than in the stationary growth phase. Then, we studied P. tricornutum common metabolic pathways and analyzed correlated enzymatic reactions between fucoxanthin synthesis and pigmentation or lipid metabolism through a genome-scale metabolic model. The integration of the computational results with liquid chromatography-mass spectrometry data revealed key compounds underlying the correlative metabolic pathways. Approximately 1000 strains were screened using fluorescence-based high-throughput method and five mutants selected had 33% or higher total carotenoids than the wild type, in which four strains remained stable in the long term and the top mutant exhibited an increase of 69.3% in fucoxanthin content compared to the wild type. The platform described in this study may be applied to the screening of other high performing diatom strains for industrial applications.

The morphology and development of Drosophila eye

Development ◽  
1967 ◽  
Vol 17 (3) ◽  
pp. 491-499
Author(s):  
E. W. Hanly ◽  
C. William Fuller ◽  
M. S. Millam Stanley
Keyword(s):  
Drosophila Melanogaster ◽  
Metabolic Pathways ◽  
Biosynthetic Pathways ◽  
Wild Type ◽  
Specific Enzyme ◽  
Type D ◽  
Red Color ◽  
Drosophila Eye ◽  
The Subject

The development of pigment in the eye of Drosophila melanogaster and other insects has been the subject of many studies and much controversy. It has been established that the red color of eyes of wild-type D. melanogaster is due to the presence of two classes of pigments, ommochromes and pteridines (Ziegler, 1961). The relationships among the various members of each class are still obscure; the biosynthetic pathways are yet to be elucidated. No specific enzyme involved in the synthesis of any member of either group has been isolated or characterized. It has been suggested, however (Hadorn, 1955), that these metabolic pathways may involve several organs, including the eye, but that the final deposition and conversion occur only in the eye. The recent development of a satisfactory technique for the culture of Drosophila organs (Schneider, 1964) has made possible the study of pigment development in the isolated eye and in eyes associated with selected organs.

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