Mzabimycins A and B, novel intracellular angucycline antibiotics produced by Streptomyces sp. PAL114 in synthetic medium containing L-tryptophan

HPLC/ESI-MS Characterization of Phenolic Compounds from Cnicus benedictus L. Roots: A Study of Antioxidant, Antibacterial, Anti-Inflammatory, and Anti-Alzheimer's Activity

The phenolic composition of Cnicus benedictus roots from four Algerian regions was investigated. Extractions were performed in both hydro-methanolic (30 : 70, v/v) and hydro-ethanolic (30 : 70, v/v) solvents. Their efficiency was determined in terms of the qualitative and quantitative composition in phenolic compounds by HPLC-LC/MS of the different extracts isolated from C. Benedictus roots. Cnicus benedictus roots extract have been characterized by high content of phenolic compounds, where the trans chalcone, 2,3-dihydro flavone, 3-hydroxy flavone and cinnamic acid constitute the major components, in addition to fourteen minor acidic compounds and flavonoids as rutin. The hydro-methanolic extract was the richest in phenolic compounds yield from C benedictus. On the other hand, hydro methanolic (30 : 70, v/v) and hydro ethanolic (30 : 70, v/v) extracts exhibited a high anti-inflammatory activity by in vitro 5-lipoxygenase inhibitory activity (IC50 : 6.05±94.16 μg/mL) as well as by in silico docking according two methods. Likewise, anti-Alzheimer activity of extracts was confirmed by this last technique taking into account the major compounds identified. Antibacterial tests revealed interesting results compared to amoxicillin for the different regions studied with a high content in trans chalcone and 3-hydroxy Flavone.

Insights into the phylogenetic diversity, biological activities, and biosynthetic potential of mangrove rhizosphere Actinobacteria from Hainan Island

Mangrove rhizosphere soils host diverse Actinobacteria tolerant to numerous stresses and are inevitably capable of exhibiting excellent biological activity by producing impressive numbers of bioactive natural products, including those with potential medicinal applications. In this study, we applied an integrated strategy of combining phylogenetic diversity, biological activities, and biosynthetic gene clusters (BGCs) screening approach to investigate the biotechnological importance of Actinobacteria isolated from mangrove rhizosphere soils from Hainan Island. The actinobacterial isolates were identifified using a combination of colony morphological characteristics and 16S rRNA gene sequence analysis. Based on the results of PCR-detected BGCs screening, type I and II polyketide synthase (PKS) and non-ribosomal synthetase (NRPS) genes were detected. Crude extracts of 87 representative isolates were subjected to antimicrobial evaluation by determining the minimum inhibitory concentration of each strain against six indicator microorganisms, anticancer activities were determined on human cancer cell lines HepG2, HeLa, and HCT-116 using an MTT colorimetric assay, and immunosuppressive activities against the proliferation of Con A-induced T murine splenic lymphocytes in vitro. A total of 287 actinobacterial isolates affiliated to 10 genera in eight families of six orders were isolated from five different mangrove rhizosphere soil samples, specififically, Streptomyces (68.29%) and Micromonospora (16.03%), of which 87 representative strains were selected for phylogenetic analysis. The crude extracts of 39 isolates (44.83%) showed antimicrobial activity against at least one of the six tested indicator pathogens, especially ethyl acetate extracts of A-30 (Streptomyces parvulus), which could inhibit the growth of six microbes with MIC values reaching 7.8 μg/mL against Staphylococcus aureus and its resistant strain, compared to the clinical antibiotic ciproflfloxacin. Furthermore, 79 crude extracts (90.80%) and 48 (55.17%) of the isolates displayed anticancer and immunosuppressive activities, respectively. Besides, four rare strains exhibited potent immunosuppressive activity against the proliferation of Con A-induced T murine splenic lymphocyte in vitro with an inhibition rate over 60% at 10 μg/mL. Type I and II polyketide synthase (PKS) and non-ribosomal synthetase (NRPS) genes were detected in 49.43, 66.67, and 88.51% of the 87 Actinobacteria, respectively. Signifificantly, these strains (26 isolates, 29.89%) harbored PKS I, PKS II, and NRPS genes in their genomes. Nevertheless, their bioactivity is independent of BGCs in this study. Our findings highlighted the antimicrobial, immunosuppressive, and anticancer potential of mangrove rhizosphere Actinobacteria from Hainan Island and the biosynthetic prospects of exploiting the corresponding bioactive natural product.

Rare Halophilic Nocardiopsis from Algerian Saharan Soils as Tools for Biotechnological Processes in Pharmaceutical Industry

The Sahara Desert, one of the most extreme ecosystems in the planet, constitutes an unexplored source of microorganisms such as mycelial bacteria. In this study, we investigated the diversity of halophilic actinobacteria in soils collected from five regions of the Algerian Sahara. A total of 23 halophilic actinobacterial strains were isolated by using a humic-vitamin agar medium supplemented with 10% NaCl. The isolated halophilic strains were subjected to taxonomic analysis using a polyphasic approach, which included morphological, chemotaxonomic, physiological (numerical taxonomy), and phylogenetic analyses. The isolates showed abundant growth in CMA (complex medium agar) and TSA (tryptic soy agar) media containing 10% NaCl, and chemotaxonomic characteristics were consistent with their assignment to the genus Nocardiopsis. Analysis of the 16S rRNA sequence of 23 isolates showed five distinct clusters and a similarity level ranging between 98.4% and 99.8% within the Nocardiopsis species. Comparison of their physiological characteristics with the nearest species showed significant differences with the closely related species. Halophilic Nocardiopsis isolated from Algerian Sahara soil represents a distinct phyletic line suggesting a potential new species. Furthermore, the isolated strains of halophilic Nocardiopsis were screened for their antagonistic properties against a broad spectrum of microorganisms by the conventional agar method (agar cylinders method) and found to have the capacity to produce bioactive secondary metabolites. Except one isolate (AH37), all isolated Nocardiopsis showed moderate to high biological activities against Pseudomonas syringae and Salmonella enterica, and some isolates showed activities against Agrobacterium tumefaciens, Serratia marcescens, and Klebsiella pneumoniae. However, no isolates were active against Bacillus subtilis, Aspergillus flavus, or Aspergillus niger. The obtained finding implies that the unexplored extreme environments such as the Sahara contain many new bacterial species as a novel drug source for medical and industrial applications.

A New Saharan Strain of Streptomyces sp. GSB-11 Produces Maculosin and N-acetyltyramine Active Against Multidrug-Resistant Pathogenic Bacteria

Multi-resistant bacterial pathogens are a major public health problem for treating nosocomial infections owing to their high resistance to antibiotics. The objective of this research was to characterize the bioactive molecules secreted by a novel moderately halophilic actinobacterium strain, designated GSB-11, exhibiting a strong antagonistic activity against several multidrug-resistant pathogenic bacteria. This potential strain was identified by phenotypic, genotypic (16S rRNA), and phylogenetic analyses. GSB-11 was related to "Streptomyces acrimycini" NBRC 12736 ^T with 99.59% similarity. Molecular screening by PCR assay demonstrated that the strain possesses two biosynthetic genes coding for NRPS and PKS-II. Two active compounds GSB11-6 and GSB11-7 were extracted from the cell-free culture supernatant of Bennett medium and purified using reversed-phase HPLC. According to spectrometric (mass spectrum) and spectroscopic (¹H NMR, ¹³C NMR, ¹H-¹H COSY, and ¹H-¹³C HMBC) spectra analyses, the compounds GSB11-6 and GSB11-7 were identified to be maculosin and N-acetyltyramine, respectively. Their minimum inhibitory concentrations (MIC) revealed interesting values against certain multidrug-resistant pathogenic bacteria. They were between 5 and 15 mg/mL for GSB11-6, 10 and 30 mg/mL for GSB11-7. To our best knowledge, this is the first study of these active substances isolated from "Streptomyces acrimycini" showing an interesting antibacterial activity. Therefore, these essential compounds could be candidates for future research against multidrug-resistant bacteria.

Diversity of Actinobacteria Isolated from Date Palms Rhizosphere and Saline Environments: Isolation, Identification and Biological Activity Evaluation

The diversity of cultural Actinobacteria in two types of Algerian Sahara environments, including saline environments and date palms rhizosphere, was investigated. In this study, a total of 40 strains of actinomycetes was isolated from different soil samples, using a rehydration and centrifugation method. Molecular identification, based on 16S rRNA gene sequence analysis, revealed that these isolates were affiliated to six clusters corresponding to eight genera, including Streptomyces, Nocardiopsis, Saccharopolyspora, Actinomadura, Actinocorallia, Micromonospora, Couchioplanes, and Planomonospora. A taxonomic analysis, based on the morphological, physiological, biochemical, and molecular investigation, of selected strains, which belong to the rare Actinobacteria, was undertaken. Four strains (CG3, A111, A93, and A79) were found to form distinct phyletic lines and represent new actinobacterial taxa. An assessment of antimicrobial proprieties of the 40 obtained actinomycetes strains, showed moderate to strong antimicrobial activities against fungi and bacteria. This study demonstrated the richness of Algerian Sahara with rare Actinobacteria, which can provide novel bioactive metabolites, to solving some of the most challenging problems of the day, such as multi-drug resistance.