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PubMedDate not supplied

[Characteristics of exogenous dormancy of Aspergillus niger conidia].

Aspergillus niger conidia are characterized by exogenous dormancy: the first stage of their germination is accomplished in twice distilled water. However, germ tube formation requires the availability of carbon and nitrogen sources. Exogenous dormancy in A. niger conidia exhibits the following peculiar features: (i) nitrogen-containing substances are active stimulators of germination; (ii) temperature-dependent changes in the lipid bilayer and in the neutral lipid composition of conidia are virtually identical to those occurring in growing mycelium under temperature stress; and (iii) the spore viability threshold does not exceed 45 degrees C; i.e., the spores are more heat-resistant than the mycelium, but they are less heat-resistant than the spores that are in the state of endogenous dormancy. According to the current classification of the types of cell metabolism arrest, the exogenous dormancy of A. niger conidia resembles the pattern of metabolism characteristic of vegetative cells during the idiophase.

Aspergillus niger↗
PubMedDate not supplied

[Zinc consumption from the nutrient medium of Trichosporon capitatum and Aspergillus niger].

The sorption capacity of the cultures Trichosporon capitatum and Aspergillus niger towards zinc dissolved in the culture liquid was studied by radio active labelling. The curves of sorption kinetics and the so-called sorption quasi-isotherms showing the dependence of zinc sorption by the microbial biomass upon zinc concentration in the liquid medium were derived. For the Aspergillus niger culture at zinc concentrations of 0.5 to 52 mug/ml the sorption quasi-isotherm was linear. The zinc extraction by microorganisms was related not only to the physico-chemical sorption but also to the zinc accumulation in the cell biopolymers. The paper presents calculations of the microbiological purification of sewage waters from zinc by means of the Aspergillus niger culture.

Aspergillus↗
PubMed2001

[Cloning and sequence analysis of the phytase phyA gene of Aspergillus niger N25].

The phyA encoding phytase of Aspergillus niger N25 was amplified by the polymerase chain reaction (PCR) with primers designed according to the sequences of the phyA in GenBank. The amplified fragment was cloned and sequenced. The results show that: the coding region is 1506 bp in size, includes a 102 bp intron, and encodes a peptide of 476 amino acid residues, in which there is a signal peptide with 19 amino acids and a mature peptide of 448 amino acids. Comparison of this sequence with the phyA of the natural A. niger NRRL3135 (GenBank Accession: M94550), the most highly secreting-phytase strain, shows that the nucleotide homology is as high as 96.746%, and the amino acid homology comes up to 97.64%. The phyA of A. niger N25 strain in this paper is appropriate to be used to construct the phytase gene-engineering bacteria.

6-Phytase↗
PubMed2003

[Application of the Unmet Obstetrical Needs method in the III neighborhood of Niamey, Niger (1999)].

West Africa has probably the highest levels of maternal mortality in the world. A new method has been developed by the Institute of Tropical Medicine of Antwerp (Belgium) that gives an estimate of the Uncovered Obstetrical Need. This technique tested in different Western African countries has been now evaluated also in an urban medical district in Niamey, capital of Niger, for the year 1999. The uncovered obstetrical need has been estimated at 15 major Obstetrical Interventions for this period; this means that 15 pregnant women didn't undergo a major surgical intervention necessary to save their life and that they probably died because of this non-intervention. We met quite a lot of problems with this new method: (i) the first problem is related to the difficulty to obtain correct demographic information: it is very difficult to estimate population growth in urban african areas, present population and number of attended births. (ii) The second difficulty came from sociocultural habits: primipare women in Niger go back to their family to deliver (and the place where their family lives is not necessarily the same as the place where they stay with their husband); it is quite possible that a number of primipare women needing a major surgical intervention didn't undergo this intervention because they delivered in their home village (and perhaps died there). (iii) At last, the estimation of a reference rate (calculated at 0.9% for Niger) implies that all women needing a major obstetrical intervention in Niamey, and having a theoretical easy access to medical infrastructures (first line as second line hospitals) present themselves when having a major obstetrical problem. This is probably "wishful thinking". The interest of this new method lies in the fact that it is a cheap technique and easy to put into practice ... provided that one disposes of medical infrastructures that collect correctly all necessary medical information.

Birth Rate↗
PubMedDate not supplied

Screening and mutagenesis of Aspergillus niger for the improvement of glucose 6-phosphate dehydrogenase production.

The strain of Aspergillus niger ZBY-7 was selected as the original strain of glucose 6-phosphate dehydrogenase production. After mutagenesis of the strain using UV irradiation and nitrosoguanidine, mutants of Aspergillus niger resistant to certain metabolic inhibitor were obtained. Five of the mutants showed increased glucose 6-phosphate dehydrogenase production. The mutant resistant to antimycin A (Aspergillus niger AM-23) produced the highest level of glucose 6-phosphate dehydrogenase (695.9% of that from the original strain).

Antifungal Agents↗
PubMed1992

[Diversity of malaria in the Sahelo-Saharan region. A review apropos of the status in Niger, West Africa].

The concept of epidemiologic facies of malaria underlines the diversity in the expression of the disease in areas where important ecological variations interfere largely with transmission. Niger is quite a border region between the afrotropical fauna from the south and the Palearctic fauna from the north. The last one filters through the mountains where it maybe represents a relic of ancient paleoclimates. Annual variations of the northern limit of Anopheles arabiensis, in the Sahelo-Saharan region including some oasis, are related to temporary breeding places produced by seasonal rainfall, after estivation during the dry season or after a long migration with the wind. An. gambiae s.s is present in the south and along the Niger river, with An. funestus, even till Zinder. The northern limit of An. nili is the Niger river. The permanent variations of the environment induce great differences in the level of transmission between an intermediate stable situation in the south to an unstable one in the north. Epidemic outbreaks appear some years in vulnerable populations. The implementation of a malaria program supposes to take account of the various eco-epidemiologic situations all over the country. Even if mortality and morbidity became lower, natural precaution in some groups of people must be preserved.

Adolescent↗
PubMed2004

[Long-term impact of a mass treatment by praziquantel on morbidity due to Schistosoma haematobium in two hyperendemic villages of Niger].

Although it is established that the treatment by praziquantel reduces the urinary lesions due to Schistosoma haematobium, the frequency of mass treatment necessary to maintain a low morbidity level remains poorly known. The objective of this work was to study the impact over three years of a single praziquantel mass treatment on schistosomiasis morbidity in two different systems of disease transmission in Niger. The study was performed in 2 villages hyperendemic for schistosomiasis in the South-West of Niger presenting respectively 2 different systems of schistosomiasis transmission: Koutoukalé-Zéno (K Zéno), located close to an irrigated area of the Niger River Valley where the transmission is permanent, and Téguey located along a temporary pond where the transmission is seasonal. After the initial evaluation (1994), we carried out a survey 3 years later (1997) except in K. Zéno where an intermediate evaluation was performed 10 months after the initial survey (1995). Approximately 300 randomised people have been examined as follows: macroscopic examination of urine and reagent sticks for macro- and micro-haematuria, filtration and microscopic examination of urine for Schistosoma eggs, and ultrasound scan of the urinary tract for morbidity. The therapeutic coverage has reached 69.9% in K. Zéno and 78.2% in Téguey. The prevalence of infestation decreased from 74.1% to 56.4 % in K. Zéno (p < 0.001) and from 65.3% to 30.4% in Téguey (p < 0.001) at the end of the 3 years. The prevalence of heavy infestation (eggs > or = 50) went in the same time from 9.9% to 12.8% (p = 0.3) in K. Zéno and from 9.1% to 3.3% in Téguey (p = 0.01). Using ultrasound scan, the prevalence of the bladder lesions reached its previous level in both villages. However the prevalence of hydronephrosis decreased from 21.1% to 3.9% in K. éno (p < 0.001) and from 12.6% to 4.2% in Téguey (p < 0.001). Three years after the single mass treatment, the morbidity did not reach the initial level. The effectiveness of the treatment is better in the pond system where the transmission is seasonal. The lesions of the upper tract decreased more slowly than the bladder lesions, but a long time after the treatment. The re-infestation induced the re-appearance of the bladder lesions sooner than the lesions of the upper tract. The periodicity of the treatment should be variable according to the transmission system. It should occur every 2 years in irrigated areas and could be delayed (3 years) in temporary ponds. The control was beneficial in the pond system and induced a significant reduction of the severe lesions.

Adolescent↗
PubMed2004

[Hypersensitivity pneumonitis induced by Aspergillus niger--a case report].

A 52-year-old woman was hospitalized because of severe cough in August 1994. She had engaged in culturing roses in greenhouses since 1968, and had developed a cough during the summer of 1990. Chest radiography showed diffuse ground-glass opacity in both lung fields, and she suffered from hypoxemia (PaO2 = 45.6 torr) while breathing room air. The lymphocyte count in the bronchoalveolar lavage fluid was increased, and transbronchial lung biopsy specimens showed lymphocyte alveolitis in the alveolar spaces. After admission, the patient's symptoms improved rapidly without medication. However, on her return to work, the cough and hypoxemia reappeared. In her rose culture, she had used Rockwool, and Aspergillus niger was detected predominantly in the Rockwool. Precipitins against the extracts of Aspergillus niger were detected with the double immunodiffusion test and the inhalation provocation test yielded clinical symptoms. Our diagnosis was hypersensitivity pneumonitis caused by Aspergillus niger.

Agricultural Workers' Diseases↗
PubMed2005

Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor.

In this paper we report the regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor. For this, the influence of dissolved oxygen concentration in a medium on intracellular pH values and consequently on overall microbial metabolism was emphasized. Intracellular pH of mycelium grown under different concentrations of dissolved oxygen in the medium was determined. Sensitivity of proteins toward proton concentration is well recognized, therefore pH influences on the activities of key regulatory enzymes of Aspergillus niger were determined at pH values similar to those detected in the cells grown under lower dissolved oxygen concentrations. The results have shown significantly reduced specific activities of hexokinase, 6-phosphofructokinase and glucose-6-phosphate dehydrogenase in more acidic environment, while pyruvate kinase was found to be relatively insensitive towards higher proton concentration. As expected, due to the reduced specific activities of regulatory enzymes under more acidic conditions, overall metabolism should be hindered in the medium with lower dissolved oxygen concentration which was confirmed by detecting the reduced specific growth rates. From the studies, we conclude that dissolved oxygen concentration affects the intracellular pH and thus growth rate of Aspergillus niger during the fermentation process.

Aspergillus niger↗
PubMed2005

[Effect of blue light on conidiation development and glucoamylase enhancement in Aspergillus niger].

Pure blue (BL) or red light (RL) were obtained by filtering blue or red fluorescent lamp light through plastic filters. With the dark condition as control, the effect of BL and RL on the Aspergillus niger were studied including soluble protein content of mycelium, glucoamylase activity, the biomass as well as sporangiophore photomorphogenesis and vegetative spore development. Irradiation with BL and RL wholly promoted glucoamylase activity together with the rise of the soluble protein content and the mycelium growth. The glucoamylase activity of mycelia culture under blue light was enhanced 2.54 times than that of control. In the phases of developmental growth (young mycelia and sporangiophores), glucoamylase activity and relative conductivity ratio of mycelium were higher under blue light than under dark, the enhanced glucoamylase activity likely stemmed from development of macrosporangiophores of Aspergillus niger promoted by blue light. In addition, the increase of glucoamylase activity under blue light was highest at the stage of macrosporangiophores forming and conidiation, then declined owing to spores aging. As to young microsporangiophores under darkness the glucoamylase activity just relatively increased and declined rapidly with age. Different from control, irradiation with blue light at the time of 72 h after inoculation was able to stimulate development of macrosporangiophore and conidium along with the rise of glucoamylase activity of Aspergillus niger.

Aspergillus niger↗
PubMed2006

Heterologous expression of Trametes versicolor laccase in Pichia pastoris and Aspergillus niger.

Convenient expression systems for efficient heterologous production of different laccases are needed for their characterization and application. The laccase cDNAs lcc1 and lcc2 from Trametes versicolor were expressed in Pichia pastoris and Aspergillus niger under control of their respective glyceraldehyde-3-phosphate dehydrogenase promoters and with the native secretion signal directing catalytically active laccase to the medium. P. pastoris batch cultures in shake-flasks gave higher volumetric activity (1.3 U/L) and a better activity to biomass ratio with glucose than with glycerol or maltose as carbon source. Preliminary experiments with fed-batch cultures of P. pastoris in bioreactors yielded higher activity (2.8 U/L) than the shake-flask experiments, although the levels remained moderate and useful primarily for screening purposes. With A. niger, high levels of laccase (2700 U/L) were produced using a minimal medium containing sucrose and yeast extract. Recombinant laccase from A. niger harboring the lcc2 cDNA was purified to homogeneity and it was found to be a 70-kDa homogeneous enzyme with biochemical and catalytic properties similar to those of native T. versicolor laccase A.

Aspergillus niger↗
PubMedDate not supplied

[Effect of pH on the enzymic activity of the fungi Trichothecium roseum and Aspergillus niger hydrolyzing nonstarch polysaccharides].

The purpose of the study was to determine optimal pH values for the enzymic activity of the fungi Trichothecium roseum and Aspergillus niger hydrolyzing nonstarch polysaccharides of barley and disrupting cell walls (cytolysis) of grain, the so called cytolytic enzymes. The effect of the acidity of the medium on the stability of these enzymes was also investigated. In this connection total cytolytic activity (i. e. total activity of the enzymes hydrolyzing nonstarch polysaccharides of cell walls of barley) and hemicellulase activity of the fungi at different pH values were measured. The activity of these enzymes in aqueous extracts from the fungal culture at optimal pH after preincubation was determined at different acidity levels. The optimum of the hemicellulase activity of both fungi was at 4.6, the optimum of the total cytolytic activity of Tr. roseum at pH 5.6 and of Asp. niger at pH 3.0. The enzymes of the fungus Asp. niger showed a far higher acid stability than those of Tr. roseum.

Aspergillus↗
PubMed1990

Comparison of the properties of glucoamylases from Rhizopus niveus and Aspergillus niger.

Some properties of the glucoamylase from Rhizopus niveus have been determined and compared with the comparable properties of the glucoamylase from Aspergillus niger. The enzymes from these organisms possess the following common properties: quantitative conversion of starch to glucose, molecular weights in the range 95,500 to 97,500, and glycoprotein structures with many oligosaccharide side chains attached to the protein moieties of the enzymes. Differences in the glucoamylases exist in electrophoretic mobility, amino acid composition, nature of carbohydrate units, and types of glycosidic linkages. Lysine, threonine, serine, glutamic acid, tyrosine, and phenylalanine differ in the two glucoamylases by 25 to 50%. Whereas the enzyme from R. niveus contains mannose and glucosamine, in the N-acetyl form, as the carbohydrate constituents, the enzyme from A. niger contains mannose, glucose, and galactose. The carbohydrate chains of the R. niveus enzyme are linked by O-glycosidic and N-glycosidic linkages to the protein, while those of the A. niger enzyme are linked by O-glycosidic linkages only. Antibodies directed against the two glucosamylases have been isolated by affinity chromatography and found to be specific for the carbohydrate units of the glucoamylases. Cross reactions did not occur between the glucoamylases and the purified antibodies.

Amino Acids↗
PubMed1990

Genetic variability in the compatibility between Schistosoma haematobium and its potential vectors in Niger. Epidemiological implications.

A populational study of the compatibility between Schistosoma haematobium and its potential vectors has been carried out in the Niger, confronting samples of S. haematobium populations from three epidemiologic foci with Bulinus populations originating from the same focus (sympatric infection) and with Bulinus populations from other foci (allopatric infections). The three transmission foci selected were irrigation canals in ricefields along the Niger river where one finds: Bulinus truncatus rohlfsi, Bulinus globosus, Bulinus forskalii and Bulinus senegalensis; temporary pools in the Sahel area where one finds B. truncatus and B. senegalensis; permanent pools of the "guelta" type in Sahara area where only B. truncatus occurs. As a compatibility test, the snail infection test was selected, with particular emphasis on optimising its reliability. Snail-infection experiments showed that B. truncatus and B. senegalensis are very good potential vectors, with infection rates ranging between 71.5 and 85.9%. B. globosus and B. forskalii, on the other hand, are totally incompatible. The mean infection percentages in the sympatric and allopatric combinations carried out with the S. haematobium-B. truncatus couple were very similar. This character strongly suggests a lack of isolation in schistosome populations and a circulation of the parasite genome through the mobility of infected human populations (Peuls and Touaregs) in Sahel zone. This study, in relation with snail surveys carried out in parallel, shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmission.

Adolescent↗
PubMed1985

Effect of iron on the activity of aconitate hydratase and synthesis of citric acid by Aspergillus niger.

Two strains of A. niger were cultivated on beet molasses medium by the surface method, and the effects of iron on the mycelium formation, the rate of sugar utilization, the activity of aconitate hydratase, and synthesis of citric acid were determined. Among various sources of di- and trivalent iron, ferrous sulphate was chosen for studies, which most effectively limited the synthesis of organic iron, ferrous sulphate was chosen for studies, which most effectively limited the synthesis of organic acids. The molasses solutions were purified with potassium ferrocyanide and FeSO4 at a concentration of 20 mg/100 ml (in terms of Fe2+) was added. It was found in both strains that such an amount of Fe2+, additionally introduced into the molasses medium, only slightly effected the synthesis of the mycelium biomass and the rate and extent of sugar utilization, when at the same time a high increase in the activity of aconitate hydratase occurred. Citric acid production, however, was strongly inhibited by this Fe2+-concentration in case of A. niger 23 (about 94%), whereas A. niger Lcz showed a relatively small decrease (about 20%).

Aconitate Hydratase↗
PubMedDate not supplied

[Use of catabolic repression in the selection of the glucoamylase-producer Aspergillus niger].

The effect of various carbon sources and cAMP on the glucoamylase synthesis in Aspergillus niger was studied to find carbon sources repressed the enzyme synthesis and conditions for the selection of catabolite stable mutants. Maltose at a concentration of 0.5% stimulated the glucoamylase synthesis, but at a concentration of 4% it repressed not only the enzyme synthesis but the growth of the parental strain on the agar medium. The more active mutant 66 was obtained as a result of treatment of Asp. niger st 6 with NG. This mutant is able to grow on the Czapek's medium containing maltose at concentrations 4 or 6%. The mutant 66 produced about 2.9 times more glucoamylase than its parent when maltose was added at 0.5% concentration to the medium. The glucoamylase synthesis in the parental strain was completely repressed under repressing conditions, while the level of the mutant strain activity was 35% from the level of enzyme activity on the medium without the repressor. The addition of cAMP (5.10(-5] resulted in a partial release of maltose (4%) repression of the glucoamylase synthesis in both strains. The results obtained indicate a possibility to select Asp niger mutants with the partially derepressed glucoamylase synthesis. Other regulation mechanisms in addition to catabolite repression may be involved in the regulation of the glucoamylase synthesis.

Aspergillus niger↗
PubMedDate not supplied

[Survey on the prevalence of sequelae of poliomyelitis of the lower limbs in school-age children in rural areas of the Department of Niamey, Niger].

An investigation of lower limb motor disorders among school age children in three rural areas of Niger has demonstrated a prevalence rate of approximately seven per thousand in the 5-9 and 10-14 years age-groups, with no significant difference in rates for boys and girls. Although severe (bilateral) paralysis is encountered only among non-attenders, no significant difference in overall prevalence is found with regard to school attendance status. Eight per cent of affected children are unable to walk and a further eight per cent need crutches or other aids. Patient histories indicate that over 90 per cent of cases occur before the child's fourth birthday; there is no indication of a modification in incidence over the past nine years. Extrapolation from the observed data indicates an annual incidence rate for paralytic poliomyelitis of the order of 45 per hundred thousand population, i.e. about 2,500 cases a year for the whole of Niger, approximately 2,000 of whom survive with a permanent disability. These rates and figures are similar to those calculated for several other african countries and are seven to ten times higher than the figures gathered from routine reports of poliomyelitis in Niger. The total number of children unable to walk unaided among the 5-14 years age-group can be estimated in 1981 at 1,600, half of whom are paralysed in such a way that they are unable to walk at all. Other preventable causes of paralysis of the lower limbs encountered include i.a. tuberculosis of the spine, sequelae of cerebrospinal meningitis and, second only to paralytic poliomyelitis in importance, trauma to peripheral nerves through faulty injection technique.

Adolescent↗
PubMed1994

Development of a mutant strain of Aspergillus niger and optimization of some physical factors for improved calcium gluconate production.

In the course of mutation studies of Aspergillus niger strain AB with ethylene imine (1:4000), a mutant A. niger AB 501, produced greater amount of calcium gluconate in the culture broth (88.0 g/lit) as against the parent strain (36.0 g/lit) by the surface culture method of fermentation. This mutant was then exposed to UV-rays and a mutant, A.niger AB 1801, was found to produce high calcium gluconate in the culture broth (120 g/lit). The optimum cultural conditions for the production of calcium gluconate by A.niger AB 1801 were pH, 6.5; period of incubation, 9 days; volume of medium in 1 litre flask, 150 ml; temperature, 30 degrees C, volume of inoculum, 7.5 ml of cell suspension containing 2.6 x 10(7) spores and age of inoculum, 6 days old spores of A. niger AB 1801. The maximum yield of calcium gluconate to the above conditions was 168 g/lit. The cultural conditions that support maximum cultural growth did not, however, give optimal yield of calcium gluconate because after having yielded the maximum of calcium gluconate the growth of organism continued to increase further.

Aspergillus niger↗