Régulation de la production d'antibiotiques dithiolopyrrolones chez saccharothrix algeriensis NRRL B-24137

Ce travail s'est donné pour objectif l'étude de l'effet de certains nutriments (acides aminés, acides organiques et acide humique) sur la production des antibiotiques dithiolopyrrolones, ainsi que l'induction de la production de nouvelles dithiolopyrrolones chez Saccharothrix algeriensis NRRL B-24137 (= DSM 44581) dans un milieu semi-synthétique. La cystine à une concentration comprise entre 0 et 5 mM favorise la production des dithiolopyrrolones en fournissant des précurseurs du noyau pyrrothine. Au-delà de cette concentration, la production des dithiolopyrrolones chute fortement. La présence de certains acides aminés comme L-proline, acide L-glutamique et DL-histidine et certains acides organiques comme 4-hydroxybenzoïque, benzentétracarboxylique, pantothénique et pivalique mène à une augmentation de la production des dithiolopyrrolones. En outre, les productions des dithiolopyrrolones sont fortement favorisées en présence de 0,25 g/L de l'acide humique. En revanche, la présence de certains acides aminés (cystéine, méthionine, éthionine, etc.) et acides organiques (pamoïque, benzensulfonique et syringique, etc.) a un effet inhibiteur sur la production des dithiolopyrrolones même à des concentrations peu élevées. Certains acides organiques s'incorporent directement au niveau de la chaîne latérale produisant ainsi l'antibiotique correspondant. Dans le milieu synthétique de base, Sa. algeriensis ne produit qu'un nombre limité de dithiolopyrrolones. L'induction de nouvelles dithiolopyrrolones a été réalisée par l'addition de certains acides aminés (cysteine et cystine) et acides organiques (benzoïque, cinnamique, 4-bromobenzoïque, etc.). Dans cette étude, dix huit principales nouvelles dithiolopyrrolones ont été obtenues. Les similarités des molécules nouvellement apparues observées dans les spectres UV -visible et les fragments de masse indiquent qu'on est en présence de molécules appartenant au même groupe des dithiolopyrrolones ou des précurseurs proches des dithiolopyrrolones. Les données ont révélés que la molécule PR 14,60 (PM = 276) est une déméthyl-benzoyl-pyrrothine, une nouvelle molécule jamais signalée. En revanche, la nouvelle dithiolopyrrolone PR 16,64 est une benzoyl-pyrrothine, une molécule produite en traces dans le milieu complexe. Des fermentations contrôlées dans des fermenteurs en batch ont été effectuées en présence de l'acide benzoïque, de l'acide tiglique, de l'acide méthacrylique et de l'acide humique (pris un à un) pour affiner les résultats obtenus en ErIenmeyers. D'après les résultats obtenus, la croissance de Sa. algeriensis dans toutes les fermentations est très rapide pendant les premières heures de culture. Les cellules de la culture témoin subissent une lyse cellulaire assez marquée alors que les cellules en présence des acides organiques se maintiennent bien. Les acides organiques en tant que source de carbone permettent la conservation de l'intégrité des cellules. Les dithiolopyrrolones ne sont produits que pendant l'idiophase. La biosynthèse de ces antibiotiques est soumise à la régulation par les acides organiques ajoutés. L'acide méthacrylique et l'acide tiglique, dans certaines conditions, augmentent la production de quelques dithiolopyrrolones. En outre, une diminution de la teneur de toutes les dithiolopyrrolones est observée après les 80 h de fermentation. Ces baisses constatées des titres sont à attribuer peut être à une dégradation ou transformation des dithiolopyrrolones. Les résultats obtenus en fermenteurs ne sont pas exactement les même que ceux obtenus en ErIenmeyers d'un point de vue qualitatif et quantitatif. En revanche, nous avons obtenu les deux nouvelles molécules induites par l'acide benzoïque (PR 14,60 et PR 16,64). ABSTRACT : This work aimed to investigate the effect of some nutriments (amino acids, organic acids and humic acid) on dithiolopyrrolone antibiotic productions and also the induction of the production of new dithiolopyrrolones produced by Saccharothrix algeriensis NRRL B-24137 (= DSM 44581) while growing on chemically defined medium. The dithiolopyrrolone productions are variables according to the nature and the concentration of used sources. Cystine at concentration of 0 to 5 mM favoured dithiolopyrrolone productions by supplying good precursors. In contrast, when it was used in excess, showing a negative effect. The presence of some amino acids (L-proline, L-glutamique and DL-histidine) and some organic acids (4-hydroxybenzoic, benzentetracarboxylic, pantothenic and pivalic) favoured the dithiolopyrrolone antibiotics. In addition, the presence of humic acid (0,25 g/L) stimulated the dithiolopyrrolone productions. In contrast, some amino acids (cysteine, methionine, ethionine, etc.) and some organic acids (pamoic, benzensulfonic, syringic, etc.) had an inhibitory effect on dithiolopyrrolone productions even at low concentrations. Some organic acids are directly incorporated on the pyrrothine radical forming the corresponding antibiotic. In semi-synthetic medium, the strain produced a limited number of dithiolopyrrolones. The induced production of new dithiolopyrrolones has been achieved by the addition of some amino acids (cysteine and cystine) and organic acids (benzoic, cinnamic, 4-bromobenzoic, etc.). In our study, eighteen principal new dithiolopyrrolones have been obtained. The similarity in UV- and mass spectra between these molecules indicated that they are belonging to the same group of dithiolopyrrolones or they are precursors of dithiolopyrrolones. The data have also revealed that the molecule PR 14,60 is demethyl-benzoyl-pyrrothine, a new molecule not reported in the literature. However, the second molecule PR 16,64 is benzoyl-pyrrothine produced in few quantity in the complex medium. The controlled batch fermentations were conducted in the presence of benzoic, tiglic, methacrylic and humic acids. The growth rate of Sa. algeriensis in all fermentations was fast during the first 10 h of fermentation. The control culture showed a partially cell lysis in comparison to cultures with organic acids. As this result, these organic acids could be used for biomass maintaining. The dithiolopyrrolone productions were observed only at idiophase. The dithiolopyrrolone biosyntheses were influenced by the addition of organic acids. The methacrylic and tiglic acids increased the dithiolopyrrolone productions in some conditions. In addition, all dithiolopyrrolone productions were decreased after 80 h of fermentation, probably due to the antibiotic degradation or transformation. The experiment in the fermentor showed some differences with results obtained in Erlenmeyers. However, the same two new dithiolopyrrolones (PR 14,60 and PR 1 6,64) obtained in Erlenmeyers was also obtained in the fermento

Aspergillus section Flavi and aflatoxins in Algerian wheat and derived products

Wheat and its derivatives are a very important staple food for North African populations. The aim of this study was to analyze populations of Aspergillus section Flavi from local wheat based on aflatoxins (AFs),cyclopiazonic acid (CPA) and sclerotia production, and also to evaluate AFs-contaminated wheat collected from two different climatic regions in Algeria. A total of 108 samples of wheat were collected during the following phases: pre-harvest, storage in silos and after processing. The results revealed that among the Aspergillus species isolated, those belonging to section Flavi were predominant. Of the 150 strains of Aspergillus section Flavi isolated, 144 were identified as Aspergillus flavus and 6 as Aspergillus tamarii. We showed that 72% and 10% of the A. flavus strains produced AFs and CPA, respectively. Among the 150 strains tested, 60 produced amounts of AFB1 ranging from 12.1 to 234.6 lg/g of CYA medium. Also, we showed that most strains produced large sclerotia. AFB1was detected by HPLC in 56.6% of the wheat samples and derived products (flour, semolina and bran) with contamination levels ranging from 0.13 to 37.42 lg/kg

Actinopolyspora saharensis sp. nov., a novel halophilic actinomycete isolated from a Saharan soil of Algeria

A novel halophilic actinomycete, strain H32T,was isolated froma Saharan soil sample collected in El-Oued province, south Algeria. The isolate was characterized by means of polyphasic taxonomy. Optimal growth was determined to occur at 28–32°C, pH 6.0–7.0 and in the presence of 15–25 %(w/v) NaCl. The strain was observed to produce abundant aerial mycelium, which formed long chains of rod-shaped spores at maturity, and fragmented substrate mycelium. The cell wall was determined to contain meso-diaminopimelic acid and the characteristic whole-cell sugars were arabinose and galactose. The predominant menaquinoneswere found to beMK-10(H4) andMK-9(H4). The predominant cellular fatty acids were determined to be anteiso C17:0, iso-C15:0 and iso-C16:0. The diagnostic phospholipid detected was phosphatidylcholine. Phylogenetic analyses based on the 16S rRNA gene sequence showed that this strain formed a distinct phyletic line within the radiation of the genus Actinopolyspora. The 16S rRNAgene sequence similarity indicated that strain H32T was most closely related to ‘Actinopolyspora algeriensis’ DSM 45476T (98.8 %) and Actinopolyspora halophila DSM 43834T (98.5 %). Furthermore, the result of DNA–DNA hybridization between strain H32T and the type strains ‘A. algeriensis’ DSM45476T, A. halophila DSM 43834T and Actinopolyspora mortivallis DSM 44261T demonstrated that this isolate represents a different genomic species in the genus Actinopolyspora. Moreover, the physiological and biochemical data allowed the differentiation of strain H32T from its closest phylogenetic neighbours. Therefore, it is proposed that strain H32T represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora saharensis sp. nov. is proposed. The type strain is H32T (=DSM 45459T=CCUG 62966T)

Pressurized Liquid Extraction for the Recovery of Carotenoids and Functional Compounds from Green and Orange Dunaliella salina Biomasses

In recent years, intensive research has been conducted on natural carotenoids extraction using several processes. Conventional extraction methods require high amounts of solvents and a long extraction time. However, pressurized liquid extraction demonstrated to be an interesting method. The extraction efficiencies of pressurized liquid for the recovery of carotenoids, from the green and the orange biomasses of the microalga Dunaliella salina DunaDZ1, are described. Organic solvents were tested including ethanol, n-hexane, ethyl acetate and a mixture of n-hexane:ethanol (3:4). Moreover, three extraction temperatures were used (90, 120 and 150 °C) at constant pressure. Extraction efficiency and extracts characterization were conducted. Results have shown that temperature has a positive effect on extraction yield. HPLC characterization showed that β-carotene is the main carotenoid in the orange biomass, and lutein in the green biomass, with the presence of other minor carotenoids in both biomasses. The highest carotenoid amounts were found in the n-hexane orange biomass extract, with β-carotene isomers as the main carotenoid (138.54 and 357.10 mg/g of dry extract, for cis and trans isomers, respectively). Otherwise, extracts obtained at the lowest tested temperature provided the best carotenoid yields. The best results for the antioxidant activity were obtained at 120 °C for orange biomass ethyl acetate extract

Kinetic study of the growth of Saccharothrix algeriensis DSM 44581 in batch fermenter on a semi-synthetic medium in the presence of tiglic acid and methacrylic acid

This work aimed to investigate the effect of some nutriments (tiglic acid and methacrylic acid) on the growth of Saccharothrix algeriensis DSM 44581 on chemically defined medium (semi-synthetic medium) by using controlled batch fermenters. The controlled batch fermentations were conducted in the presence of tiglic and methacrylic acids. The growth rate of S. algeriensis in all fermentations was fast during the first 10 h of fermentation. The control culture showed a partially cell lysis in comparison to cultures with organic acids. This result showing that these organic acids could be used for biomass maintaining. The formation of biomass was influenced by the addition of organic acids. The experiment in the fermentor showed some differences with results obtained in Erlenmeyers

Effects of Temperatures and Rainfall Variability on the Abundance and Diversity of Caelifera (Insecta, Orthoptera) in Three Natural Environments in the Mzab Valley, Septentrional Sahara (Algeria)

The climatic condition is assumed as the main factor responsible for development and survival of insects; this investigation was conducted to study the responses of Caelifera to temperatures and precipitation variations during 2017 in three natural environments of Mzab Valley, Ghardaïa, Algeria. A total of 22 grasshopper species were collected, representing four families and eight subfamilies. The subfamily Oedipodinae was the dominant, followed by Pyrgomorphinae and Thrinchinae. Two species: Sphingonotus rubescens and Sphingonotus savignyi occurred frequently in the three sites. However, only one accidental species, Eunapiodes sp. was found. According to our observations, it is clear that the grasshopper diversity was higher in July and August coinciding with the increase in temperature. In such conditions, the precipitation has less influence on species diversit

Actinopolyspora righensis sp. nov., a novel halophilic actinomycete isolated from Saharan soil in Algeria

A novel halophilic actinomycete strain, H23T, was isolated from a Saharan soil sample collected in Djamaˆa (Oued Righ region), El-Oued province, South Algeria. Strain H23T was identified as a member of the genus Actinopolyspora by a polyphasic approach. Phylogenetic analysis showed that strain H23T had 16S rRNA gene sequence similarities ranging from 97.8 % (Actinopolyspora xinjiangensis TRM 40136T) to 94.8 % (Actinopolyspora mortivallis DSM 44261T). The strain grew optimally at pH 6.0–7.0, 28–32°C and in the presence of 15–25 % (w/v) NaCl. The substrate mycelium was well developed and fragmented with age. The aerialmyceliumproduced long, straight or flexuous spore chains with non-motile, smooth-surfaced and rod-shaped spores. Strain H23T had MK-10 (H4) and MK-9 (H4) as the predominant menaquinones. The whole microorganism hydrolysates mainly consisted of meso-diaminopimelic acid, galactose and arabinose. The diagnostic phospholipid detected was phosphatidylcholine. The major cellular fatty acids were anteiso-C17:0 (37.4 %), iso-C17:0 (14.8 %), iso-C15:0 (14.2 %), and iso-C16:0 (13.9 %). The genotypic and phenotypic data show that the strain represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora righensis sp. nov. is proposed, with the type strain H23T (=DSM 45501T = CCUG 63368T = MTCC 11562T)

Antimicrobial activities of novel bipyridine compounds produced by a new strain of Saccharothrix isolated from Saharan soil

The actinobacterium strain ABH26 closely related to Saccharothrix xinjiangensis, isolated from an Algerian Saharan soil sample, exhibited highly antagonist activity against Gram-positive bacteria, yeasts and filamentous fungi. Its ability to produce antimicrobial compounds was investigated using several solid culture media. The highest antimicrobial activity was obtained on Bennett medium. The antibiotics secreted by strain ABH26 on Bennett medium were extracted by methanol and purified by reverse-phase HPLC using a C18 column. The chemical structures of the compounds were determined after spectroscopic (1H NMR, 13C NMR, 1H-1H COSY and 1H-13C HMBC spectra), and spectrometric (mass spectrum) analyses. Two new cyanogriside antibiotics named cyanogriside I (1) and cyanogriside J (2), were characterized along with three known caerulomycins, caerulomycin A (3), caerulomycin F (4) and caerulomycinonitrile (5). This is the first report of cyanogrisides and caerulomycins production by a member of the Saccharothrix genus. The minimum inhibitory concentrations (MIC) of these antibiotics were determined against pathogenic microorganisms

Saccharothrix algeriensis NRRL B-24137, the first non-Streptomyces actinobacterium, produces holomycin after cystine feeding

Saccharothrix algeriensis NRRL B-24137 is an actinobacterium isolated from Algerian Saharan soil. This strain has the ability to produce several dithiolopyrrolone antibiotic derivatives depending on the precursors added to the culture medium. This group of antibiotics is known for their potent antimicrobial and anticancer activities. Holomycin is a member of the dithiolopyrrolone group of antibiotics, and has already been isolated from several species of actinobacteria belonging to the genus Streptomyces and also from some Gram-negative bacteria. In this study, holomycin was produced for the first time in the culture broth of a non-Streptomyces actinobacteria. This antibiotic was induced by adding 5 mM of L-cystine as precursor to the semi-synthetic fermentation broth of Sa. algeriensis NRRL B-24137 and then fully identified after HPLC purification. The minimum inhibitory concentrations (MIC) of holomycin were determined against several pathogenic microorganisms, including Escherichia coli ATCC 10536 Klebsiella pneumoniae CIP 82.91, Listeria monocytogenes CIP 82110, Staphylococcus aureus CIP 7625, Aspergillus carbonarius M333, Fusarium culmorum FC1, Candida albicans IPA 200. This antibiotic showed a broad-spectrum antimicrobial activity, inhibiting a variety of Gram-positive and Gram-negative bacteria, and micro-fungi

Antifungal activity of a Saharan strain of Actinomadura sp. ACD1 against toxigenic fungi and other pathogenic microorganisms

A new strain of actinobacteria, designated ACD1, was isolated from a Saharan soil sample in the Hoggar region (Algeria). Morphological study led to this strain being classified as a member of the Actinomadura genus. Phylogenetic analysis based on the 16S rRNA gene showed that the strain is closely related to Actinomadura sediminis DSM 45500T (98.5% sequence similarity). Furthermore, strain ACD1 presented a strong activity against mycotoxigenic and phytopathogenic fungi, including Aspergillus and Fusarium strains, and other pathogenic microorganisms. The kinetics of antimicrobial activity were investigated on ISP-2, Bennett and TSB media. Four solvents (n-hexane, dichloromethane, ethyl acetate and n-butanol) were used for the extraction of the produced antibiotic. The highest antimicrobial activity was obtained using the butanolic extract from the ISP-2 medium after seven days of fermentation culture. The active antibiotic was purified by reverse-phase HPLC using a C18 column. The UV-visible and mass spectra were determined. The minimum inhibitory concentrations (MIC) of this antibiotic were determined against pathogenic microorganisms