A Molecule of the Viridomycin Family Originating from a Streptomyces griseus-Related Strain Has the Ability to Solubilize Rock Phosphate and to Inhibit Microbial Growth.

Some soil-borne microorganisms are known to have the ability to solubilize insoluble rock phosphate and this process often involves the excretion of organic acids. In this issue, we describe the characterization of a novel solubilizing mechanism used by a Streptomyces strain related to Streptomyces griseus isolated from Moroccan phosphate mines. This process involves the excretion of a compound belonging to the viridomycin family that was shown to play a major role in the rock phosphate bio weathering process. We propose that the chelation of the positively charged counter ions of phosphate constitutive of rock phosphate by this molecule leads to the destabilization of the structure of rock phosphate. This would result in the solubilization of the negatively charged phosphates, making them available for plant nutrition. Furthermore, this compound was shown to inhibit growth of fungi and Gram positive bacteria, and this antibiotic activity might be due to its strong ability to chelate iron, a metallic ion indispensable for microbial growth. Considering its interesting properties, this metabolite or strains producing it could contribute to the development of sustainable agriculture acting as a novel type of slow release bio-phosphate fertilizer that has also the interesting ability to limit the growth of some common plant pathogens.

Arthrographis curvata and Rhodosporidium babjevae as New Potential Fungal Lipase Producers for Biotechnological Applications

Abstract Fungi have always attracted a lot of attention as they are able to produce a vast repertoire of enzymes that find a broad spectrum of uses in biotechnological and industrial fields. Undoubtedly, one of the most promising biocatalysts is the lipase, which has been widely used for the biotransformation of a number of commercial products due to its high stability, high catalytic efficiency, versatility and selectivity, making it one of the most attractive and best-studied enzymes. In this study we report the isolation and molecular identification of new lipase-producing fungi from different environmental samples from Morocco. The production and activity of extracellular lipases, at different parameters, was evaluated using the Rhodamine B agar, submerged fermentation and biochemical methods. Two fungal strains Arthrographis curvata and Rhodosporidium babjevae, were isolated and found to produce large amounts of lipases. The optimal activity of the extracellular lipase was detected at 40°C and pH 9.0 for A. curvata and at 40 °C and pH 8.0 for R. babjevae. This study add new information at the growing list of fungal species producing lipases with improved physicochemical proprieties which could constitute a new line of research for further studies and to be exploited for industrial or bioremediation purposes.

Petroleum sludge bioremediation and its toxicity removal by landfill in gunder semi-arid conditions.

In this investigation, petroleum sludge landfilling was carried out in order to assess the biodegradation degree and the final product quality. The microbial analysis showed a good microorganism proliferation which reinforces the biodegradation process. The total mesophilic and thermophilic microflora evaluated symmetrically as they increased at the intermediate stage and decreased at the final. The C/N and NH4+/NO3-ratios decreased while the polymerization degree increased at the end of the landfilling process. The total polyphenols and total petroleum C6 to C22hydrocarbons were removed by 71.6% and 73% respectively, and that affected the reduction of the phytotoxicity in a positive way. All these changes are in agreement with the efficiency of the biotransformation process and showed that petroleum sludge and filling reduced the toxic organic compounds and led to a stable final product.

Early events induced by the toxin deoxynivalenol lead to programmed cell death in Nicotiana tabacum cells.

Deoxynivalenol (DON) is a mycotoxin affecting animals and plants. This toxin synthesized by Fusarium culmorum and Fusarium graminearum is currently believed to play a decisive role in the fungal phytopathogenesis as a virulence factor. Using cultured cells of Nicotiana tabacum BY2, we showed that DON-induced programmed cell death (PCD) could require transcription and translation processes, in contrast to what was observed in animal cells. DON could induce different cross-linked pathways involving (i) reactive oxygen species (ROS) generation linked, at least partly, to a mitochondrial dysfunction and a transcriptional down-regulation of the alternative oxidase (Aox1) gene and (ii) regulation of ion channel activities participating in cell shrinkage, to achieve PCD.

Enzymatic synthesis of dithiolopyrrolone antibiotics using cell-free extract of Saccharothrix algeriensis NRRL B-24137 and biochemical characterization of two pyrrothine N-acyltransferases in this extract.

Saccharothrix algeriensis NRRL B-24137 produces naturally different dithiolopyrrolone derivatives. The enzymatic activity of pyrrothine N-acyltransferase was determined to be responsible for the transfer of an acyl group from acyl-CoA to pyrrothine core. This activity was also reported to be responsible for the diversity of the dithiolopyrrolone derivatives. Based on this fact, nine dithiolopyrrolone derivatives were produced in vitro via the crude extract of Sa. algeriensis. Three of them have never been obtained before by natural fermentation: acetoacetyl-pyrrothine, hydroxybutyryl-pyrrothine, and dimethyl thiolutin (holomycin). Two acyltransferase activities, acetyltransferase and benzoyltransferase catalyzing the incorporation of linear and cyclic acyl groups to the pyrrothine core, respectively, were biochemically characterized in this crude extract. The first one is responsible for formation of acetyl-pyrrothine and the second for benzoyl-pyrrothine. Both enzymes were sensitive to temperature changes: For example, the loss of acetyltransferase and benzoyltransferase activity was 53% and 80% respectively after pre-incubation of crude extract for 60 min at 20°C. The two enzymes were more active in neutral and basal media (pH 7-10) than in the acidic one (pH 3-6). The optimum temperature and pH of acetyltransferase were 40°C and 7, with a Km value of 7.9 µM and a Vmax of 0.63 µM/min when acetyl-CoA was used as limited substrate. Benzoyltransferase had a temperature and a pH optimum at 55°C and 9, a Km value of 14.7 µM, and a Vmax of 0.67 µM/min when benzoyl- CoA was used as limited substrate.

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

A novel halophilic actinomycete strain, H23(T), was isolated from a Saharan soil sample collected in Djamâa (Oued Righ region), El-Oued province, South Algeria. Strain H23(T) was identified as a member of the genus Actinopolyspora by a polyphasic approach. Phylogenetic analysis showed that strain H23(T) had 16S rRNA gene sequence similarities ranging from 97.8 % (Actinopolyspora xinjiangensis TRM 40136(T)) to 94.8 % (Actinopolyspora mortivallis DSM 44261(T)). 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 aerial mycelium produced long, straight or flexuous spore chains with non-motile, smooth-surfaced and rod-shaped spores. Strain H23(T) had MK-10 (H4) and MK-9 (H4) as the predominant menaquinones. The whole micro-organism 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 H23(T) (=DSM 45501(T) = CCUG 63368(T) = MTCC 11562(T)).

Saccharothrix saharensis sp. nov., an actinomycete isolated from Algerian Saharan soil.

The taxonomic position of a novel actinomycete, strain SA152(T), isolated from a sample of Algerian Saharan soil, was determined using a polyphasic taxonomic approach. The strain produced abundant aerial mycelium and fragmented substrate mycelium on most media tested. Chemotaxonomically and phylogenetically, the strain was related to the members of the genus Saccharothrix. Results of 16S rRNA gene sequence comparison revealed that strain SA152(T) shared the highest degree of 16S rRNA gene sequence similarity with Saccharothrix xinjiangensis NBRC 101911(T) (99.3 %) and Saccharothrix texasensis NRRL B-16134(T) (98.9 %). However, DNA-DNA hybridization studies showed only 16.2 % relatedness with S. xinjiangensis DSM 44896(T) and 33.9 % relatedness with S. texasensis DSM 44231(T). Based upon genotypic and phenotypic differences from other members of the genus, a novel species, Saccharothrix saharensis sp. nov., is proposed, with SA152(T) ( = DSM 45456(T) = CCUG 60213(T)) as the type strain.

Actinopolyspora mzabensis sp. nov., a halophilic actinomycete isolated from an Algerian Saharan soil.

A halophilic actinomycete strain, designated H55(T), was isolated from Saharan soil sampled in the Mzab region (Ghardaïa, southern Algeria) and was characterized in a taxonomic study using a polyphasic approach. The cell wall was determined to contain meso-diaminopimelic acid and the characteristic whole-cell sugars were arabinose and galactose. The predominant menaquinones were found to be MK-10(H4) and MK-9(H4). The predominant cellular fatty acids were determined to be anteiso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. The diagnostic phospholipid detected was phosphatidylcholine. The morphological and chemotaxonomic characteristics of the strain were consistent with those of members of the genus Actinopolyspora, and 16S rRNA gene sequence analysis confirmed that strain H55(T) was a member of this genus. DNA-DNA hybridization values between strain H55(T) and the type strains of the nearest species of the genus Actinopolyspora, Actinopolyspora erythraea and A. alba, were clearly below the 70 % threshold. The genotypic and phenotypic data showed that the organism represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora mzabensis sp. nov. is proposed, with the type strain H55(T) ( = DSM 45460(T) = CCUG 62965(T)).

Saccharothrix hoggarensis sp. nov., an actinomycete isolated from Saharan soil.

An actinomycete, designated SA181(T), was isolated from Saharan soil in the Hoggar region (south Algeria) and was characterized taxonomically by using a polyphasic approach. The morphological and chemotaxonomic characteristics of the isolate were consistent with the genus Saccharothrix, and 16S rRNA gene sequence analysis confirmed that strain SA181(T) was a novel member of the genus Saccharothrix. DNA-DNA hybridization values between strain SA181(T) and its closest phylogenetic neighbours, the type strains of Saccharothrix longispora, Saccharothrix texasensis and Saccharothrix xinjiangensis, were clearly below the 70 % threshold. The genotypic and phenotypic data showed that the isolate represents a novel species of the genus Saccharothrix, for which the name Saccharothrix hoggarensis sp. nov. is proposed, with the type strain SA181(T) ( = DSM 45457(T)  = CCUG 60214(T)).

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

A novel halophilic actinomycete, strain H32(T), was isolated from a 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 menaquinones were found to be MK-10(H4) and MK-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 rRNA gene sequence similarity indicated that strain H32(T) was most closely related to 'Actinopolyspora algeriensis' DSM 45476(T) (98.8 %) and Actinopolyspora halophila DSM 43834(T) (98.5 %). Furthermore, the result of DNA-DNA hybridization between strain H32(T) and the type strains 'A. algeriensis' DSM 45476(T), A. halophila DSM 43834(T) and Actinopolyspora mortivallis DSM 44261(T) demonstrated that this isolate represents a different genomic species in the genus Actinopolyspora. Moreover, the physiological and biochemical data allowed the differentiation of strain H32(T) from its closest phylogenetic neighbours. Therefore, it is proposed that strain H32(T) represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora saharensis sp. nov. is proposed. The type strain is H32(T) (=DSM 45459(T)=CCUG 62966(T)).

Actinopolyspora algeriensis sp. nov., a novel halophilic actinomycete isolated from a Saharan soil.

A halophilic actinomycete strain designated H19(T), was isolated from a Saharan soil in the Bamendil region (Ouargla province, South Algeria) and was characterized taxonomically by using a polyphasic approach. The morphological and chemotaxonomic characteristics of the strain were consistent with those of members of the genus Actinopolyspora, and 16S rRNA gene sequence analysis confirmed that strain H19(T) was a novel species of the genus Actinopolyspora. DNA-DNA hybridization value between strain H19(T) and the nearest Actinopolyspora species, A. halophila, was clearly below the 70 % threshold. The genotypic and phenotypic data showed that the organism represents a novel species of the genus Actinopolyspora for which the name Actinopolyspora algeriensis sp. nov. is proposed, with the type strain H19(T) (= DSM 45476(T) = CCUG 62415(T)).

Chemical composition and in vitro evaluation of the antioxidant and antimicrobial activities of Eucalyptus gillii essential oil and extracts.

In this study, essential oil and various extracts (hexane, petroleum ether, acetone, ethanol, methanol and water) of Eucalyptus gilii were screened for their chemical composition, antimicrobial and antioxidant activities. The essential oil chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID), respectively. Thirty four compounds were identified, corresponding to 99.5% of the total essential oil. Tannins [104.9-251.3 g catechin equivalent (CE)/Kg dry mass], flavonoids [3.3-34.3 g quercetin equivalent (QE)/Kg dry mass], phenolics [4.7-216.6 g gallic acid equivalent (GAE)/Kg dry mass] and anthocyannins [1.2-45.3 mg cyanidin-3-glucoside equivalent (C3GE)/Kg dry mass] of various extracts were investigated. Free radical scavenging capacity of all samples was determinedt. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, the IC50 of essential oil was 163.5 ± 10.7 mg/L and in the 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate (ABTS) assay, it was 94.7 ± 7.1 mg/L. Among the various extracts, the water extract showed the best result (IC50 = 11.4 ± 0.6 mg/L) in the DPPH assay which was comparable to vitamin C (IC50 = 4.4 ± 0.2 mg/L). The antimicrobial activities were evaluated against different bacterial and fungal strains. Gram positive bacteria were found to be more sensitive to the essential oil and extracts than Gram negative ones. Anthocyanins seem to have a major effect on the growth of Bacillus subtilis (R2 = 0.79). A significant antifungal activity was observed against the yeast and fungi. Correlations between chemical composition and antioxidant activities were studied and R2 values were about 0.96 for the effect of phenolics on the DPPH assay.

Season's variation impact on Citrus aurantium leaves essential oil: chemical composition and biological activities.

Citrus aurantium leaves' essential oils (EOs) were evaluated for chemical composition and antioxidant and antibacterial activities. The vegetable material, taken 5 times during the year, has undergone the hydrodistillation to prepare EO. Chemical characterization by gas chromatography/mass spectrometry and GC/flame ionization detection allowed the identification of 46 compounds, and a notable quantitative and qualitative differences between the different Petitgrain samples according to the harvest time. Linalool (43.2% to 65.97%), linalyl acetate (0.77% to 24.77%), and α-terpineol (9.29% to 12.12%) were the main components. The most important number of components was registered for summer EOs (July and September). The 5 EOs submitted biological activities screening, namely, antioxidant and antimicrobial activities. Weak antioxidant activities (IC(50) values >10000 mg/L) were registered by both 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate assays, mostly because the weak amount of phenols in EOs. Antibacterial activities (12 microorganisms) were registered against Gram-positive bacteria [Bacillus subtilis (MIC = 2.7 mg/mL), Staphylococcus aureus (4.8 mg/mL)], and moderated ones against yeasts [Saccharomyces cerevisiae (9.2 mg/mL)] and fungi [Mucor ramannianus (5 mg/mL)]. Positive correlations between the identified compounds and the antimicrobial activities were noted. Many compounds were correlated to antimicrobial activity mainly caryophyllene oxide against Escherichia coli (R(2) = 0.99), S. cerevisiae (R(2) = 0.99), and Fusarium culmorum (R(2) = 0.99).

Saccharothrix sp. PAL54, a new chloramphenicol-producing strain isolated from a Saharan soil.

An actinomycete strain designated PAL54, producing an antibacterial substance, was isolated from a Saharan soil in Ghardaïa, Algeria. Morphological and chemical studies indicated that this strain belonged to the genus Saccharothrix. Analysis of the 16S rDNA sequence showed a similarity level ranging between 96.9 and 99.2% within Saccharothrix species, with S. longispora DSM 43749(T), the most closely related. DNA-DNA hybridization confirmed that strain PAL54 belonged to Saccharothrix longispora. It showed very strong activity against pathogenic Gram-positive and Gram-negative bacteria responsible for nosocomial infections and resistant to multiple antibiotics. Strain PAL54 secreted the antibiotic optimally during mid-stationary and decline phases of growth. One antibacterial compound was isolated from the culture broth and purified by HPLC. The active compound was elucidated by uv-visible and NMR spectroscopy and by mass spectrometry. The results showed that this compound was a D: (-)-threo chloramphenicol. This is the first report of chloramphenicol production by a Saccharothrix species.

Quantification of Fusarium graminearum and Fusarium culmorum by real-time PCR system and zearalenone assessment in maize.

Zearalenone (ZEA) is a mycotoxin produced by some species of Fusarium, especially by Fusarium graminearum and F. culmorum. ZEA induces hyperoestrogenic responses in mammals and can result in reproductive disorders in farm animals. In the present study, a real-time PCR (qPCR) assay has been successfully developed for the detection and quantification of Fusarium graminearum based on primers targeting the gene PKS13 involved in ZEA biosynthesis. A standard curve was developed by plotting the logarithm of known concentrations of F. graminearum DNA against the cycle threshold (Ct) value. The developed real time PCR system was also used to analyze the occurrence of zearalenone producing F. graminearum strains on maize. In this context, DNA extractions were performed from thirty-two maize samples, and subjected to real time PCR. Maize samples also were analyzed for zearalenone content by HPLC. F. graminearum DNA content (pg DNA/ mg of maize) was then plotted against ZEA content (ppb) in maize samples. The regression curve showed a positive and good correlation (R²=0.760) allowing for the estimation of the potential risk from ZEA contamination. Consequently, this work offers a quick alternative to conventional methods of ZEA quantification and mycological detection and quantification of F. graminearum in maize.

Taxonomic study and partial characterization of antimicrobial compounds from a moderately halophilic strain of the genus Actinoalloteichus

A moderately halophilic actinomycete strain designated AH97 was isolated from a saline Saharan soil, and selected for its antimicrobial activities against bacteria and fungi. The AH97 strain was identified by morphological, chemotaxonomic and phylogenetic analyses to the genus Actinoalloteichus. Analysis of the 16S rDNA sequence of strain AH97 showed a similarity level ranging between 95.8 percent and 98.4 percent within Actinoalloteichus species, with A. hymeniacidonis the most closely related. The comparison of the physiological characteristics of AH97 with those of known species of Actinoalloteichus showed significant differences. Strain AH97 showed an antibacterial and antifungal activity against broad spectrum of microorganisms known to be human and plant pathogens. The bioactive compounds were extracted from the filtrate culture with n-butanol and purified using thin layer chromatography and high pressure liquid chromatography procedures. Two active products were isolated, one hydrophilic fraction (F1) and another hydrophobic (F2). Ultraviolet-visible, infrared, mass and ÕH and 13C nuclear magnetic resonance spectroscopy studies suggested that these molecules were the dioctyl phthalate (F2) and an aminoglycosidic compound (F1).

Isolation, taxonomy, and antagonistic properties of halophilic actinomycetes in Saharan soils of Algeria.

The diversity of a population of 52 halophilic actinomycetes was evaluated by a polyphasic approach, which showed the presence of members of the Actinopolyspora, Nocardiopsis, Saccharomonospora, Streptomonospora, and Saccharopolyspora genera. One strain was considered to be a new member of the last genus, and several other strains seemed to be new species. Furthermore, 50% of strains were active against a broad range of indicators and contained genes encoding polyketide synthetases and nonribosomal peptide synthetases.

Purification and structure elucidation of three naturally bioactive molecules from the new terrestrial Streptomyces sp. TN17 strain.

Thirty litres of fermentation broth was extracted from the newly isolated Streptomyces sp. strain TN17 and various separation and purification steps led to the isolation of three pure bioactive compounds (1-3). Compound 1: cyclo (L-Leu-L-Arg), a diketopiperazine 'DKP' derivative; 2: di-(2-ethylhexyl) phthalate, a phthalate derivative; and 3: cyclo 1-[2-(cyclopentanecarbonyl-3-phenyl-propionyl]-pyrrolidine-2-carboxylic acid (1-carbamoyl-propyl)-amide, a cyclic tetrapeptide derivative. The chemical structure of these three active compounds was established on the basis of spectroscopic studies (MS and NMR) and by comparison with data from the literature. According to our biological studies, the pure compounds (1-3) possess antibacterial and antifungal activities.

New dithiolopyrrolone antibiotics induced by adding sorbic acid to the culture medium of Saccharothrix algeriensis NRRL B-24137.

Dithiolopyrrolone antibiotics, produced by several microorganisms, are known for their strong antimicrobial activities. This class of antibiotics generated new interest after the discovery of their anticancer and antitumor properties. In this study, four new antibiotics were purified from the fermentation broth of Saccharothrix algeriensis NRRL B-24137 and characterized as dithiolopyrrolone derivatives. These new dithiolopyrrolone antibiotics were induced by adding sorbic acid, as precursor, at a concentration of 5 mM to the semi-synthetic medium. The analysis of the induced antibiotics was carried out by HPLC. The maximal production of the antibiotics PR2, PR8, PR9 and PR10 was 0.08±0.04, 0.21±0.04, 0.13±0.03 and 0.09±0.00 mg L(-1) , respectively, obtained after 8 days of fermentation. The chemical structures of these antibiotics were determined by (1) H- and (13) C-nuclear magnetic resonance, mass and UV-visible data. The four new dithiolopyrrolone antibiotics - PR2, PR8, PR9 and PR10 - were characterized, respectively, as crotonyl-pyrrothine, sorbyl-pyrrothine, 2-hexonyl-pyrrothine and 2-methyl-3-pentenyl-pyrrothine. The minimum inhibitory concentrations of the new induced antibiotics were determined.

Eucalyptus oleosa essential oils: chemical composition and antimicrobial and antioxidant activities of the oils from different plant parts (stems, leaves, flowers and fruits).

Essential oils obtained by hydrodistillation from the different parts (stems, adult leaves, immature flowers and fruits) of Eucalyptus oleosa were screened for their antioxidant and antimicrobial properties and their chemical composition. According to GC-FID and GC-MS, the principal compound of the stem, immature flowers and the fruit oils was 1,8-cineole, representing 31.5%, 47.0% and 29.1%, respectively. Spathulenol (16.1%) and γ-eudesmol (15.0%) were the two principal compounds of adult leaves oil. In the DPPH (1,1-diphenyl-2-picrylhydrazyl) assay, the oils of the four parts showed moderate antioxidant activity. In the ABTS (2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate) assay, the most active part was the adult leaves, with a IC(50) value 13.0 ± 0.6 mg/L, followed by stems (IC(50) = 43.5 ± 1.4 mg/L). The essential oils showed a better antibacterial activity against Gram-positive and Gram-negative bacteria, and a significant antifungal activity also was observed against yeast-like fungi. A strong correlations between oxygenated monoterpenes and antimicrobial activity (especially 1,8-cineole) were noted (R2 = 0.99, 0.97 and 0.79 for B. subtilis, P. aeruginosa and C. albicans, respectively).