Academic literature on the topic 'Locus niger'
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Journal articles on the topic "Locus niger"
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Silva, Josué J. da, Beatriz T. Iamanaka, Larissa S. Ferranti, Fernanda P. Massi, Marta H. Taniwaki, Olivier Puel, Sophie Lorber, Jens C. Frisvad, and Maria Helena P. Fungaro. "Diversity within Aspergillus niger Clade and Description of a New Species: Aspergillus vinaceus sp. nov." Journal of Fungi 6, no. 4 (December 17, 2020): 371. http://dx.doi.org/10.3390/jof6040371.
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Diversity of species within Aspergillus niger clade, currently represented by A. niger sensu stricto and A. welwitshiae, was investigated combining three-locus gene sequences, Random Amplified Polymorphic DNA, secondary metabolites profile and morphology. Firstly, approximately 700 accessions belonging to this clade were investigated using calmodulin gene sequences. Based on these sequences, eight haplotypes were clearly identified as A. niger (n = 247) and 17 as A. welwitschiae (n = 403). However, calmodulin sequences did not provide definitive species identities for six haplotypes. To elucidate the taxonomic position of these haplotypes, two other loci, part of the beta-tubulin gene and part of the RNA polymerase II gene, were sequenced and used to perform an analysis of Genealogical Concordance Phylogenetic Species Recognition. This analysis enabled the recognition of two new phylogenetic species. One of the new phylogenetic species showed morphological and chemical distinguishable features in comparison to the known species A. welwitschiae and A. niger. This species is illustrated and described as Aspergillus vinaceus sp. nov. In contrast to A. niger and A. welwitschiae, A. vinaceus strains produced asperazine, but none of them were found to produce ochratoxin A and/or fumonisins. Sclerotium production on laboratory media, which does not occur in strains of A. niger and A. welwitschiae, and strictly sclerotium-associated secondary metabolites (14-Epi-hydroxy-10,23-dihydro-24,25-dehydroaflavinine; 10,23-Dihydro-24,25-dehydroaflavinine; 10,23-Dihydro-24,25-dehydro-21-oxo-aflavinine) were found in A. vinaceus. The strain type of A. vinaceus sp. nov. is ITAL 47,456 (T) (=IBT 35556).
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Emmanuel, Aniwetalu, Ilechukwu Juliet, Oguadinma Vivian, Chiadikobi Kingsley, and Nnaji Ezechimelu. "Spectral analysis of Rayleigh waves in south-eastern parts of Niger delta, Nigeria." International Journal of Advanced Geosciences 6, no. 1 (December 27, 2017): 51. http://dx.doi.org/10.14419/ijag.v6i1.8776.
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Interference of ground roll energy on true seismic reflection records has continued to pose a serious challenge to exploration geophysicists. In view of this, amplitude and power spectra of the Rayleigh waves which are the precursor of the ground roll energy were derived from over 70 raw monitor records and plotted as a function of frequency. The objective is to determine the locus of ground energy in the seismic records, analyse their dispersion pattern and suggests viable ways of suppressing them. The results of the amplitude spectrum plots revealed that Rayleigh waved exhibit oscillatory behavior with very high-amplitude values, which correspond to the locus of ground roll energy. This energy is confined to very low frequency range of about 4-9Hz. The Power spectrum which was given as the square of the amplitude as a function of frequency showed appreciable lobes of breaths of the ground roll energy of about 0.5-0.7cm and their trend of dispersions. The power spectrum plots revealed several peaks excluding the early peaks that are direct indication of ground roll energy. The plots showed pronounced and constant decline in energy levels with increasing frequency and reaching very low decibel values of -60Db to -80Db at frequency range of 50Hz. This indicates that the environment is dispersive in nature which probably results from velocity layering. This is a precursor to seismic noise which among others can be suppressed in the field by designing filters with sharper cut off characteristics.
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Vongsangnak, Wanwipa, Margarita Salazar, Kim Hansen, and Jens Nielsen. "Genome-wide analysis of maltose utilization and regulation in aspergilli." Microbiology 155, no. 12 (December 1, 2009): 3893–902. http://dx.doi.org/10.1099/mic.0.031104-0.
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Maltose utilization and regulation in aspergilli is of great importance for cellular physiology and industrial fermentation processes. In Aspergillus oryzae, maltose utilization requires a functional MAL locus, composed of three genes: MALR encoding a regulatory protein, MALT encoding maltose permease and MALS encoding maltase. Through a comparative genome and transcriptome analysis we show that the MAL regulon system is active in A. oryzae while it is not present in Aspergillus niger. In order to utilize maltose, A. niger requires a different regulatory system that involves the AmyR regulator for glucoamylase (glaA) induction. Analysis of reporter metabolites and subnetworks illustrates the major route of maltose transport and metabolism in A. oryzae. This demonstrates that overall metabolic responses of A. oryzae occur in terms of genes, enzymes and metabolites when the carbon source is altered. Although the knowledge of maltose transport and metabolism is far from being complete in Aspergillus spp., our study not only helps to understand the sugar preference in industrial fermentation processes, but also indicates how maltose affects gene expression and overall metabolism.
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Kumar, Sunil, Tejaswani Saragadam, and Narayan S. Punekar. "Novel Route for Agmatine Catabolism in Aspergillus niger Involves 4-Guanidinobutyrase." Applied and Environmental Microbiology 81, no. 16 (June 5, 2015): 5593–603. http://dx.doi.org/10.1128/aem.03987-14.
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ABSTRACTAgmatine, a significant polyamine in bacteria and plants, mostly arises from the decarboxylation of arginine. The functional importance of agmatine in fungi is poorly understood. The metabolism of agmatine and related guanidinium group-containing compounds inAspergillus nigerwas explored through growth, metabolite, and enzyme studies. The fungus was able to metabolize and grow onl-arginine, agmatine, or 4-guanidinobutyrate as the sole nitrogen source. Whereas arginase defined the only route for arginine catabolism, biochemical and bioinformatics approaches suggested the absence of arginine decarboxylase inA. niger. Efficient utilization by the parent strain and also by its arginase knockout implied an arginase-independent catabolic route for agmatine. Urea and 4-guanidinobutyrate were detected in the spent medium during growth on agmatine. The agmatine-grownA. nigermycelia contained significant levels of amine oxidase, 4-guanidinobutyraldehyde dehydrogenase, 4-guanidinobutyrase (GBase), and succinic semialdehyde dehydrogenase, but no agmatinase activity was detected. Taken together, the results support a novel route for agmatine utilization inA. niger. The catabolism of agmatine by way of 4-guanidinobutyrate to 4-aminobutyrate into the Krebs cycle is the first report of such a pathway in any organism.A. nigerGBase peptide fragments were identified by tandem mass spectrometry analysis. The corresponding open reading frame from theA. nigerNCIM 565 genome was located and cloned. Subsequent expression of GBase in bothEscherichia coliandA. nigeralong with its disruption inA. nigerfunctionally defined the GBase locus (gbu) in theA. nigergenome.
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D’hooge, Elizabet, Pierre Becker, Dirk Stubbe, Anne-Cécile Normand, Renaud Piarroux, and Marijke Hendrickx. "Black aspergilli: A remaining challenge in fungal taxonomy?" Medical Mycology 57, no. 6 (December 11, 2018): 773–80. http://dx.doi.org/10.1093/mmy/myy124.
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AbstractAspergillus section Nigri is a taxonomically difficult but medically and economically important group. In this study, an update of the taxonomy of A. section Nigri strains within the BCCM/IHEM collection has been conducted. The identification accuracy of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was tested and the antifungal susceptibilities of clinical isolates were evaluated. A total of 175 strains were molecularly analyzed. Three regions were amplified (ITS, benA, and caM) and a multi-locus phylogeny of the combined loci was created by using maximum likelihood analysis. The in-house MALDI-TOF MS reference database was extended and an identification data set of 135 strains was run against a reference data set. Antifungal susceptibility was tested for voriconazole, itraconazole, and amphotericin B, using the EUCAST method. Phylogenetic analysis revealed 18 species in our data set. MALDI-TOF MS was able to distinguish between A. brasiliensis, A. brunneoviolaceus, A. neoniger, A. niger, A. tubingensis, and A. welwitschiae of A. sect. Nigri. In the routine clinical lab, isolates of A. sect. Nigri are often identified as A. niger. However, in the clinical isolates of our data set, A. tubingensis (n = 35) and A. welwitschiae (n = 34) are more common than A. niger (n = 9). Decreased antifungal susceptibility to azoles was observed in clinical isolates of the /tubingensis clade. This emphasizes the importance of identification up to species level or at least up to clade level in the clinical lab. Our results indicate that MALDI-TOF MS can be a powerful tool to replace classical morphology.
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COLLARD, J. M., Z. MAMAN, A. ABANI, H. B. MAINASARA, S. DJIBO, H. YACOUBA, R. MAITOURNAM, et al. "Microbiological and epidemiological investigation of the Neisseria meningitidis serogroup A epidemic in Niger in 2009: last wave before the introduction of the serogroup A meningococcal conjugate vaccine?" Epidemiology and Infection 139, no. 11 (January 20, 2011): 1656–60. http://dx.doi.org/10.1017/s0950268810003092.
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SUMMARYThe 2009 meningitis season in Niger was characterized by an early onset, beginning in the very first weeks of the year and peaking from the 12th to the 15th week with 5655 clinical cases over the 4 weeks. From 1 January 2009 to 28 June 2009 (week 26), a total of 13 733 clinical cases of meningitis were reported to the national epidemiological surveillance system with a case-fatality rate of 4·2%. During the season 25 of the 42 health districts reached the epidemic threshold and 11 the alert threshold. Reactive mass vaccination campaigns involving a total of 5 166 741 doses of the polysaccharide meningococcal bivalent (A+C) vaccine progressively controlled the outbreak in most parts of the country. A total of 3755 cerebrospinal fluid samples representing 28·1% of the suspected meningitis cases were analysed. Serogroup A meningococci were the causative agent in 97·5% of the meningococcal cases. Multi-locus sequence typing of 26 meningococal serogroup A strains showed 25 sequence type (ST)7 and one ST2859, both sequence types belonging to the ST5 clonal complex (CC5) of subgroup III. This is the largest epidemic observed in Niger since those of 1995–1996 (59 948 notified cases) and 2000 (14 633 notified cases).
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Olivier de Sardan, Jean-Pierre. "Rivalries of proximity beyond the household in Niger: political elites and thebaab-izeypattern." Africa 87, no. 1 (January 27, 2017): 120–36. http://dx.doi.org/10.1017/s0001972016000723.
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AbstractIn Niger, there is an increasing rejection ofpolitik(a term with highly pejorative connotations): that is, party politics and the politics of democracy, characterized by personal rivalries and power struggles between clans and factions. But there is a direct link (albeit not a causal one) between the social perceptions of intra-familial rivalries and the social perceptions of political rivalries. The archetypical relationship among thebaab-izey(children of one father but different mothers) is characterized by competition and jealousy. This is a product of the latent rivalry that pits co-wives against each other. Polygamy is clearly at odds with a number of received ideas and clichés about ‘the African family’ as primarily a locus of support and solidarity. Such formal social norms may reign in public situations, but in private de facto practical norms give rise to subtle discriminations and the omnipresence of more or less hidden conflicts within the family. The same is true for the political microcosm of Niger. While the public norm of the concern for the public good is supposed to regulate political behaviours, rivalry and jealousy are structural components of the political world. Thebaab-izeypattern is frequently used in reference to politicians. Political conflicts are above all personal/factional conflicts in which friends and supporters are implicated, and are rivalries of proximity. In the familial space as in the political space, ‘magico-religious entrepreneurs’ (i.e. experts in the occult) are merely an ‘accelerator’ of these conflicts: they reinforce suspicions about the familial or political entourage, which, in turn, intensify rivalries.
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Meyer, Vera, Mark Arentshorst, Simon J. Flitter, Benjamin M. Nitsche, Min Jin Kwon, Cristina G. Reynaga-Peña, Salomon Bartnicki-Garcia, Cees A. M. J. J. van den Hondel, and Arthur F. J. Ram. "Reconstruction of Signaling Networks Regulating Fungal Morphogenesis by Transcriptomics." Eukaryotic Cell 8, no. 11 (September 11, 2009): 1677–91. http://dx.doi.org/10.1128/ec.00050-09.
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ABSTRACT Coordinated control of hyphal elongation and branching is essential for sustaining mycelial growth of filamentous fungi. In order to study the molecular machinery ensuring polarity control in the industrial fungus Aspergillus niger, we took advantage of the temperature-sensitive (ts) apical-branching ramosa-1 mutant. We show here that this strain serves as an excellent model system to study critical steps of polar growth control during mycelial development and report for the first time a transcriptomic fingerprint of apical branching for a filamentous fungus. This fingerprint indicates that several signal transduction pathways, including TORC2, phospholipid, calcium, and cell wall integrity signaling, concertedly act to control apical branching. We furthermore identified the genetic locus affected in the ramosa-1 mutant by complementation of the ts phenotype. Sequence analyses demonstrated that a single amino acid exchange in the RmsA protein is responsible for induced apical branching of the ramosa-1 mutant. Deletion experiments showed that the corresponding rmsA gene is essential for the growth of A. niger, and complementation analyses with Saccharomyces cerevisiae evidenced that RmsA serves as a functional equivalent of the TORC2 component Avo1p. TORC2 signaling is required for actin polarization and cell wall integrity in S. cerevisiae. Congruently, our microscopic investigations showed that polarized actin organization and chitin deposition are disturbed in the ramosa-1 mutant. The integration of the transcriptomic, genetic, and phenotypic data obtained in this study allowed us to reconstruct a model for cellular events involved in apical branching.
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Agunbiade, T. A., B. S. Coates, K. S. Kim, D. Forgacs, V. M. Margam, L. L. Murdock, M. N. Ba, et al. "The spatial genetic differentiation of the legume pod borer, Maruca vitrata F. (Lepidoptera: Crambidae) populations in West Africa." Bulletin of Entomological Research 102, no. 5 (April 17, 2012): 589–99. http://dx.doi.org/10.1017/s0007485312000156.
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AbstractThe legume pod borer, Maruca vitrata, is an endemic insect pest that causes significant yield loss to the cowpea crop in West Africa. The application of population genetic tools is important in the management of insect pests but such data on M. vitrata is lacking. We applied a set of six microsatellite markers to assess the population structure of M. vitrata collected at five sites from Burkina Faso, Niger and Nigeria. Observed polymorphisms ranged from one (marker 3393) to eight (marker 32008) alleles per locus. Observed and expected heterozygosities ranged from 0.0 to 0.8 and 0.0 to 0.6, respectively. Three of the loci in samples from Nigeria and Burkina Faso deviated significantly from Hardy-Weinberg Equilibrium (HWE), whereas no loci deviated significantly in samples from Niger. Analysis of molecular variance (AMOVA) indicated that 67.3% level of the genetic variation was within individuals compared to 17.3% among populations. A global estimate of FST=0.1 (ENA corrected FST=0.1) was significant (P⩽0.05) and corroborated by pairwise FST values that were significant among all possible comparisons. A significant correlation was predicted between genetic divergence and geographic distance between subpopulations (R2=0.6, P=0.04), and cluster analysis by the program STRUCTURE predicted that co-ancestry of genotypes were indicative of three distinct populations. The spatial genetic variance among M. vitrata in West Africa may be due to limited gene flow, south-north seasonal movement pattern or other reproductive barriers. This information is important for the cultural, chemical and biological control strategies for managing M. vitrata.
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Meyer, Vera, Franziska Wanka, Janneke van Gent, Mark Arentshorst, Cees A. M. J. J. van den Hondel, and Arthur F. J. Ram. "Fungal Gene Expression on Demand: an Inducible, Tunable, and Metabolism-Independent Expression System for Aspergillus niger." Applied and Environmental Microbiology 77, no. 9 (March 4, 2011): 2975–83. http://dx.doi.org/10.1128/aem.02740-10.
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ABSTRACTFilamentous fungi are the cause of serious human and plant diseases but are also exploited in biotechnology as production platforms. Comparative genomics has documented their genetic diversity, and functional genomics and systems biology approaches are under way to understand the functions and interaction of fungal genes and proteins. In these approaches, gene functions are usually inferred from deletion or overexpression mutants. However, studies at these extreme points give only limited information. Moreover, many overexpression studies use metabolism-dependent promoters, often causing pleiotropic effects and thus limitations in their significance. We therefore established and systematically evaluated a tunable expression system forAspergillus nigerthat is independent of carbon and nitrogen metabolism and silent under noninduced conditions. The system consists of two expression modules jointly targeted to a defined genomic locus. One module ensures constitutive expression of the tetracycline-dependent transactivator rtTA2S-M2, and one module harbors the rtTA2S-M2-dependent promoter that controls expression of the gene of interest (the Tet-on system). We show here that the system is tight, responds within minutes after inducer addition, and allows fine-tuning based on the inducer concentration or gene copy number up to expression levels higher than the expression levels of thegpdApromoter. We also validate the Tet-on system for the generation of conditional overexpression mutants and demonstrate its power when combined with a gene deletion approach. Finally, we show that the system is especially suitable when the functions of essential genes must be examined.
Dissertations / Theses on the topic "Locus niger"
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Caillier, Pascal. "Rôle de la substance noire pars reticulata dans les comportements d'orientation visuellement déclenchés chez le singe." Paris 6, 1986. http://www.theses.fr/1986PA066455.
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Mavoungou, Roger. "Contribution a l'etude de la substance noire reticulee : controle exerce sur cette structure par le striatum : modification de son activite apres lesion de la voie nigrostriee ou traitement par un neuroleptique." Paris 6, 1988. http://www.theses.fr/1988PA066409.
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Chez les patients atteints de la maladie de parkinson, les cellules de la substance noire compacte disparaissent progressivement et leurs terminaisons dopaminergiques, qui se projettent vers le striatum, degenerent. Il est etudie si ces desordres induisent des modifications des activites striatales afferentes. Pour cela, chez, des rats ayant un dysfonctionnement du striatum, on etudie l'activite des cellules de l'un des principaux relais de cette voie, la substance noire reticulee. La dysfonction du striatum a ete obtenue par 3 techniques: depression envahissante appliquee electivement au niveau des corps stries; lesions pharmacologiques (6-hydroxydopamine) de la voie nigro-striatale; administration d'halogenidol neuroleptique
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Thibaut, Florence. "Système dopaminergique nigro-striatal : étude des récepteurs D1 et des transporteurs de l'amine." Rouen, 1996. http://www.theses.fr/1996ROUES017.
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Afin d'étudier, chez l'homme, le système dopaminergique nigro-striatal, nous avons choisi deux marqueurs neuronaux et un marqueur post synaptique : le [3H] GBR 12783, marqueur sélectif du transporteur de la dopamine (DA ); la [3H] dihydrotétrabénazine (TBZOH), marqueur sélectif du transporteur vésiculaire des monoamines; le [3H] SCH 23390, ligand antagoniste sélectif du récepteur D1 de la dopamine. Nous avons montré que la liaison du [3H] GBR 12783 au transporteur de la dopamine n'était pas affectée dans les 24h suivant la mort et la conservation du cerveau (du rat) à température ambiante, ce qui autorise des études post-mortem. Dans le putamen de sujets parkinsoniens, il existe une diminution de 50 % de la liaison du [3H] GBR 12783, (comparativement aux sujets sains) corrélée au stade évolutif de la maladie. Nous avons observé une densité importante de sites de liaison de la [3H] TBZOH dans l'aire tegmentale ventrale et plus encore dans la substantia nigra (S. N. ) pars compacta, particulièrement au sein de sa région médiane riche en immunoréactivité de la tyrosine hydroxylase (TH). Chez le parkinsonien, la diminution des sites de liaison de la [3H] TBZOH est moindre que la baisse de l'immunoréactivité de la TH, suggérant qu'un mécanisme de compensation de la dénervation pourrait exister. La répartition des récepteurs D1 dans les noyaux dopaminergiques du mésencéphale humain (A8-A9-A10) a montré leur plus forte densité dans la substance noire (S. N. ) (A9) (surtout dans la pars reticulata) au contact des dendrites des neurones dopaminergiques de la pars compacta. La densité des sites de liaison du [3H] SCH 23390 n'étant pas réduite chez un parkinsonien étudié, mais étant diminuée chez un patient atteint de chorée de Huntington, confirme que ces récepteurs D1 n'ont pas statut d'autorécepteurs mais sont associés à des neurones non dopaminergiques striato-nigraux. Dans la perspective d'utiliser ces différents marqueurs in vivo chez l'homme, nous avons évalué chez l'animal, les interactions entre la dopamine extracellulaire et des ligands du système de capture de la dopamine ([3H] mazindol et [3H] cocaïne) ou des récepteurs D1 (le [3H] SCH 23390). Les variations du taux de dopamine synaptique induites expérimentalement n'ont pas modifié la liaison in vivo de ces différents ligands dans le striatum. Confirme que ces récepteurs D1 n'ont pas statut d'autorécepteurs mais sont associés à des neurones non dopaminergiques striato-nigraux. Dans la perspective d'utiliser ces différents marqueurs in vivo chez l'homme, nous avons évalué chez l'animal, les interactions entre la dopamine extracellulaire et des ligands du système de capture de la dopamine ([3H] mazindol et [3H] cocaïne) ou des récepteurs D1 (le [3H] SCH 23390). Les variations du taux de dopamine synaptique induites expérimentalement n'ont pas modifié la liaison in vivo de ces différents ligands dans le striatum.
Conference papers on the topic "Locus niger"
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Ako, Emily, Erasmus Nnanna, Odumodu Somtochukwu, and Akinmade Moradeke. "Taming the Monster: Arresting Excessive Sand Production Problem in ARAMU037." In SPE Nigeria Annual International Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/207095-ms.
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Abstract Chemical Sand Consolidation (SCON) has been used as a means of downhole sand control in Niger Delta since the early 70s. The countries where SCON has been used include Nigeria (Niger Delta), Gabon (Gamba) and UK (North Sea). SCON provides grain-to-grain cementation and locks formation fines in place through the process of adsorption of the sand grains and subsequent polymerization of the resin at elevated well temperatures. The polymerized resin serves to consolidate the surfaces of the sand grain while retaining permeability through the pore spaces. In a typical Niger Delta asset, over 30% of the wells may be completed with SCON. A high percentage are still producing without failure since installation from1970s. Where the original SCON jobs have failed, re-consolidation has also been carried out successfully. Chemical Sand Consolidation development has evolved over the years from: Eposand 112A and B, Eposand 212A and B, Wellfix 2000, Wellfix 3000, Sandstop (resin based), Sandtrap 225, 350 & 500 (resin based) and lately Sandtrap 225,350, 500 (solvent based) and Sandtrap ABC (aqueous based). There have been mixed results experienced with the deployment of either of the latest recipes of SCON. This was due to the fact that the conventional deployment work procedure was followed with the tendency for one-size-fits-all approach to the treatment. This paper details the challenges faced with sand production in ARAMU037, the previous interventions and how an integrated approach to the design and delivery of the most recent intervention restored the way to normal production. The well has now produced for about 2 years with minimal interruption with the activity paying out in less than 6 months. The paper also recommends the best practice for remedial sand control especially for wells in mature assets.