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% and 98.4% 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 1H and 13C nuclear magnetic resonance spectroscopy studies suggested that these molecules were the dioctyl phthalate (F2) and an aminoglycosidic compound (F1)

Chemical composition and antimicrobial activity of the essential oil from leaves of Algerian Melissa officinalis L.

The essential oil obtained from leaves of Melissa officinalis L. (Family of Lamiaceae) growing in Algeria, was investigated for its chemical composition and in vitro antimicrobial activity. The chemical composition was determined by hydro-distillation and analyzed by GC/MS and GC-FID. Sixty-three compounds were identified in the essential oil, representing 94.10 % of the total oil and the yields were 0.34 %. The major component was geranial (44.20 %). Other predominant components were neral (30.20 %) and citronellal (6.30 %). The in vitro antimicrobial activity was determined by paper disk agar diffusion testing and minimum inhibitory concentration (MIC) using 7 bacteria (3 Gram-positive and 4 Gram-negative), 2 yeasts and 3 fungi. The results showed that the essential oil presented high antimicrobial activity against all microorganisms targeted mainly against five human pathogenic bacteria, one yeast Candida albicans and two phytopathogenic fungi tested. The minimum inhibitory concentrations (MIC) ranged from 1.00 to 5.00 μL/mL

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)

Activité antimicrobienne de Streptomyces sp. PAL111 d'origine saharienne contre divers microorganismes cliniques et toxinogènes résistants aux antibiotiques

Objectif. - Étude de la taxonomie et de l'activité de l'isolat d'actinomycète PAL111 contre divers microorganismes pathogènes et toxinogènes pour l'homme et multirésistants aux antibiotiques. Matériel et méthodes. - L'étude taxonomique de l'isolat PAL111 est réalisée sur la base de critères phénotypiques et moléculaires. Les tests contre les microorganismes pathogènes sont effectués sur les milieux ISP-2 et Bennett. Les cinétiques de production de l'antibiotique sont réalisées sur milieu ISP-2. L'antibiotique est mis en évidence par bioautographie et par révélation chimique, puis purifié par chromatographie sur couche épaisse de gel de silice et sur colonne de Séphadex LH20. Les concentrations minimales inhibitrices (CMI) sont déterminées contre les germes pathogènes. Résultats. - Sur la base des caractéristiques phénotypiques et moléculaires, l'isolat PAL111 est rapproché de l'espèce Streptomyces ambofaciens. Il présente une forte activité contre Candida albicans, les champignons filamenteux et les bactéries à Gram positif et à Gram négatif. L'activité optimales est obtenue en fin de phase exponentielle de croissance et début de phase de déclin. Les bioautographies ont montré la présence d'un antibiotique à activité antibactérienne et antifongique. Cet antibiotique est hydrophile et de nature osidique et aminé. Les CMI obtenues se situent entre 2 et 20 μg/mL pour les levures, 10 et 50 μg/Ml pour les champignons filamenteux, 2 et 10 μg/mL pour les bactéries à Gram positif et 20 et 75 μg/mL pour les bactéries à Gram négatif. Conclusion: L'activité intéressante de PAL111 contre les germes pathogènes et la nature hydrophile de l'antibiotique qu'il sécrète incite à la poursuite des études sur cette molécule bioactive

Halophilic Actinomycetes in 1 Saharan Soils of Algeria: Isolation, Taxonomy and Antagonistic Properties

The diversity of a population of 52 halophilic actinomycetes was evaluated by a polyphasic approach, which showed the presence of Actinopolyspora, Nocardiopsis, Saccharomonospora, Streptomonospora and Saccharopolyspora genera. One strain was considered to be a new member of the last genus and several other strains seem 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

Taxonomy and chemical characterization of antibiotics of Streptosporangium Sg 10 isolated from a Saharan soil

A new actinomycete strain designated Sg 10, producing antimicrobial substances was isolated from an Algerian soil. Morphological and chemical studies indicated that strain Sg 10 belonged to the genus Streptosporangium. The comparison of its physiological characteristics with those of known species of Streptosporangium showed significant differences with the nearest species Streptosporangium carneum. Analysis of the 16S rDNA sequence of strain Sg 10 showed a similarity level ranging between 96.3% and 97.8% within Streptosporangium species, with S. carneum the most closely related. However, the phylogenetic analysis indicated that strain Sg 10 represent a distinct phyletic line suggesting a new genomic species. The antimicrobial activity of strain Sg 10 showed an antibacterial activity against Gram-positive bacteria as well as an antifungal one. Four active products were isolated from the culture broth using various separation procedures. On the basis of UV-VIS spectrometry, infrared spectroscopy and chemical revelations, the antibiotics were classified in the group of glycosylated aromatics

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

Development of formulations based on Streptomyces rochei strain PTL2 spores for biocontrol of Rhizoctonia solani damping-off of tomato seedlings

Rhizoctonia solani is one of the most problematic soil-borne pathogenic fungi for several crop cultures worldwide. This study highlights the effectiveness of high-antagonistic Streptomyces rochei strain PTL2, isolated from root tissues of Panicum turgidum, in controlling the R. solani damping-off and growth promotion of tomato (cv. Marmande) seedlings. The isolate PTL2 was characterised for in vitro biocontrol and plant growth-promoting traits. It exhibited remarkable positive results in all trials, including production of hydrogen cyanide, siderophores, 1-aminocyclopropane-1-carboxylate deaminase and phytohormones, chitinolytic activity and inorganic phosphate solubilisation. PTL2 spores were formulated as wettable talcum powder, sodium alginate pellets and sodium alginate-clay pellets. Their abilities in the biocontrol of R. solani and plant growth promotion were investigated in autoclaved and non-autoclaved soils. Talcum powder and sodium alginate pellets significantly reduced the damping-off severity index compared to a positive control. The talcum powder exhibited the highest protective activity, reducing the disease incidence from 89.3% to 14.1%, whereas chemical seed treatment with Thiram® provided a disease incidence of 16.7%. Furthermore, the talc-based powder formulation resulted in greatest increases in the root length, shoot length and dry weight of seedlings. The interesting biocontrol potential and growth enhancement of tomato seedlings open up promising perspectives for the possible application of talcum powder formulation based on PTL2 spores in crop improvement

Potential of endophytic Streptomyces spp. for biocontrol of Fusarium root rot disease and growth promotion of tomato seedlings

Sixteen endophytic actinobacteria isolated from roots of native plants were evaluated for their antagonistic potential against soil-borne phytopathogenic fungi. Among them, three strong antagonistic isolates were selected and characterised for in vitro plant-growth-promoting and biocontrol traits, including production of hydrogen cyanide, indole-3-acetic acid and siderophores, chitinase and β-1,3-glucanase activities, and inorganic phosphate solubilisation. In all trials, the strain Streptomyces sp. SNL2 revealed promising features. The selected actinobacteria were investigated for the biocontrol of Fusarium oxysporum f. sp. radicis lycopersici and for growth promotion of tomato (Solanum lycopersicum L. cv. Aïcha) seedlings in autoclaved and non-autoclaved soils. All seed-bacterisation treatments significantly reduced the root rot incidence compared to a positive control (with infested soil), and the isolate SNL2 exhibiting the highest protective activity. It reduced the disease incidence from 88.5% to 13.2%, whereas chemical seed treatment with Thiram® provided 14.6% disease incidence. Furthermore, isolate SNL2 resulted in significant increases in the dry weight, shoot and root length of seedlings. 16S rDNA sequence analysis showed that isolate SNL2 was related to Streptomyces asterosporus NRRL B-24328T (99.52% of similarity). Its interesting biocontrol potential and growth enhancement of tomato seedlings open up attractive uses of the strain SNL2 in crop improvement