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

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)

Production of vineomycin A1 and chaetoglobosin A by Streptomyces sp. PAL114

An actinobacteria strain PAL114, isolated from a Saharan soil in Algeria, produces bioactive compounds. Morphological and chemical studies indicated that this strain belongs to the genus Streptomyces. Analysis of the 16S rRNA gene sequence showed a similarity level of 99.8 % with S. griseoflavus LMG 19344T, the most closely related species. Two bioactive compounds, named P44 and P40, were extracted by dichloromethane from the cell-free supernatant broth and were purified by HPLC. Minimum inhibitory concentrations (MIC) of the compounds were determined against pathogenic and toxigenic microorganisms, most of which are multiresistant to antibiotics. The P40 fraction showed a strong activity especially against Candida albicans, Bacillus subtilis, and Staphylococcus aureus and has lower MIC values than those of P44 against most microorganisms tested. Chemical structures of compounds were determined based on spectroscopic and spectrometric analyses (UV-visible, mass, 1H, and 13C NMR spectra). The compounds P44 and P40 were identified as vineomycin A1 and chaetoglobosin A, respectively. Vineomycin A1 is known to be produced by some Streptomyces species. However, chaetoglobosin A is known to be produced only by fungi belonging to the genera Chaetomium, Penicillium, and Calonectria. This is the first time that chaetoglobosin A, known for its antimicrobial, anticancer, and cytotoxic effects, is reported in prokaryotes

Plant-growth-promoting potential of endosymbiotic actinobacteria isolated from sand truffles (Terfezia leonis Tul.) of the Algerian Sahara

Seven endosymbiotic actinobacteria were isolated from sand truffles (Terfezia leonis Tul.) harvested in the Hassi R’Mel region of the Algerian Sahara. Morphological characteristics and chemotaxonomical analysis indicated that all isolates were members of the Streptomyces genus. All the isolated actinobacteria were initially screened in vitro for antifungal capacities, chitinolytic activities, siderophore production, and synthesis of plant-growth regulators (indole-3-acetic acid and gibberellic acid). The isolate Streptomyces sp. TL7 exhibited a remarkable profile with positive results in all trials, while the others showed variable responses to assays. In vivo trials were then carried out with the isolates to evaluate their root colonization abilities and plant-growth-promoting potential on tomato (cv. Marmande) seedlings. The results showed that all these Streptomyces strains could be isolated successfully from inside the roots of inoculated tomato seedlings. However, the plant-growth-promoting effect varied depending on the treatment. Seeds surface-coated with spores of Streptomyces sp. strain TL7 showed the highest performance, with significantly increased (P < 0.05) shoot and root lengths, and seedling fresh and dry weights. The taxonomic position based on 16S rDNA sequence analysis and phylogenetic studies indicated that strain TL7 was related to Streptomyces neopeptinius KNF 2047T (99.0 % similarity). The interesting antifungal properties and plant-growth promotion traits shown by Streptomyces sp. strain TL7 may indicate a potential for its possible use as plant-growth-promoting agent, especially for tomato seedlings

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)

Deoxynivalenol-producing ability of Fusarium culmorum strains and their impact on infecting barley in Algeria

The cereal-pathogenic Fusarium culmorum (W.G. Smith), causal agent of various blights and rot diseases, is considered as a chronic fungus of economic concern worldwide including North African countries such as Algeria. This pathogen produces a wide range of mycotoxins, amongst which the type B-trichothecene deoxynivalenol (DON). In addition to its acute and chronic side effects in livestock and humans, DON is believed to play a determinant role in the pathogenesis toward Triticeae. However, regardless its significant occurrence and impact, little is known about trichothecenes-producing ability of F. culmorum infecting cereals in Algeria. The PCR assay based on Tri genes of 12 F. culmorum strains (designated Fc1-Fc12), which were recovered from several cropping areas of North Algeria, revealed their trichothecenes-producing ability with 3-AcDON genotype. The molecular prediction was confirmed by HPLC analysis. All strains were able to produce the toxin at detectable levels. Strains Fc1 and Fc12 were the highest producers of this mycotoxin with 220 and 230 µg g(-1), respectively. The evaluation of pathogenic ability of strains through a barley infesting experiment exhibited the significant disease impact of most strains. Significant correlation between the DON-producing ability of strains and the increase in both disease severity (r = 0.88, P = 0.05) and disease occurrence (r = 0.70, P = 0.05) was observed. Chemotyping of F. culmorum isolates and evaluation of their pathogenic ability are reported for the first time for isolates from Algeria, and highlights the important potential of F. culmorum to contaminate cultivated cereal with DON trichothecenes

Polyphasic characterization of Aspergillus section Flavi isolated from animal feeds in Algeria

In Algeria, little information is available on the population structure of Aspergillus section Flavi in raw materials and resultant animal feeds. A total of 172 isolates belonging to Aspergillus section Flavi were recovered from 57 animal feeds and identified on the basis of macro and micro‐morphological characters, mycotoxin production and genetic relatedness. For the molecular analysis, sequencing of the calmodulin gene (CaM) and the internal transcribed spacer (ITS) regions were performed for representative isolates. Four distinct morphotypes were distinguished: Aspergillus flavus (78.5%), Aspergillus tamarii (19.2%), Aspergillus parasiticus (1.7%), and Aspergillus alliaceus (0.6%). All A. flavus isolates were of the L type and no correlation between sclerotia production and aflatoxigenicity was observed. Our results showed that 68% of the A. flavus strains produced aflatoxins B (AFB), and 72.7% were cyclopiazonic acid (CPA) producers. The three isolates of A. parasiticus were able to produce AFB and aflatoxins G but not CPA whereas, all the strains of A. tamarii produced only CPA. The obtained results revealed the presence of different species of Aspergillus section Flavi, among which were aflatoxin producers. This study provides evidence useful for considerations in aflatoxin control strategies

Nocardiopsis algeriensis sp. nov., an alkalitolerant actinomycete isolated from Saharan soil

An alkalitolerant actinomycete strain, designated B32T, was isolated from a Saharan soil sample collected from Adrar province (South of Algeria), and then investigated using a polyphasic taxonomic approach. The strain was observed to produce short chains of spores on the dichotomous branched aerial mycelium and formed a fragmented substrate mycelium. The optimum NaCl concentration for growth was found to be 0–5 % (w/v) and the optimum growth temperature and pH were found to be 25–35 °C and 7.0–10.0 °C, respectively. The diagnostic diamino acid in the cell-wall peptidoglycan was identified as meso-diaminopimelic acid. The predominant menaquinones of strain B32T were identified as MK-10 (H4) and MK-11 (H4). The major fatty acids were found to be iso-C16:0 and anteiso-C15:0. The diagnostic phospholipids detected were phosphatidylcholine, phosphatidylmethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The chemotaxonomic properties of strain B32T are consistent with those shared by members of the genus Nocardiopsis. 16S rRNA gene sequence analysis indicated that strain B32T is most closely related to Nocardiopsis alba DSM 43377T (98.7 %), Nocardiopsis lucentensis DSM 44048T (98.6 %), Nocardiopsis aegyptia DSM 44442T (98.6 %), Nocardiopsis sinuspersici HM6T (98.6 %) and Nocardiopsis arvandica HM7T (98.5 %). However, the DNA–DNA relatedness values between strain B32T and the closely related type strains were 17.9, 14.6, 31.1, 27.1 and 14.1 %, respectively. Based on the combined genotypic and phenotypic evidence, it is proposed that strain B32T should be classified as representative of a novel species, for which the name Nocardiopsis algeriensis sp. nov. is proposed. The type strain is B32T (=DSM 45462T = CECT 8712T)

Isolation, Classification and Antagonistic Properties of Alkalitolerant Actinobacteria from Algerian Saharan Soils

The Sahara, one of the most extreme environments on Earth, constitutes an unexplored source of alkalitolerant actinobacteria. In this work, we studied the diversity of alkalitolerant actinobacteria in various soils collected from different regions of the Algerian Sahara. A total of 29 alkalitolerant actinobacterial strains were isolated by using a complex agar medium. The diversity of these actinobacteria was evaluated using a polyphasic approach, which included morphological, chemotaxonomic, physiological (numerical taxonomy) and 16S rRNA gene analyses. The isolates which were assigned to the genus Nocardiopsis, shared relatively low 16S rRNA gene sequences similarities compared to closely related species suggesting that they belonged to putatively new species. All of the strains were tested for antibiotic activity against a broad range of microorganisms and screened for genes encoding polyketide synthases and non-ribosomal peptide synthetases and found to have the potential to produce secondary metabolites. Consequently, the study supports the view that extreme environments contain many novel actinobacteria, which represent an unexplored source for the discovery of biologically active compounds

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