Taxonomy and antimicrobial activities of a new Streptomyces sp. TN17 isolated in the soil from an oasis in Tunis

An actinomycete strain referred to as TN17 was screened for its antimicrobial activities. The taxonomic status of this strain was established. The organism was found to have morphological and chemotaxonomic characteristics typical of Streptomycetes. Based on the 16S rRNA nucleotide sequences, Streptomyces sp. TN17 was found to have a relationship with Streptomyces lilaceus, Streptomyces gobitricini and Streptomyces lavendofoliae. Combined analysis of the 16 S rRNA gene sequence (FN687757), phylogenetic analysis, fatty acids profile and physiological tests indicated that there are genotypic and phenotypic differences between TN17 and neighboring Streptomyces species’ neighbors. Therefore, TN17 is a novel species: Streptomyces sp. TN17 (=DSM 42020T=CTM50229T). A cultured extract of this strain inhibits the growth of several Gram positive and Gram negative bacteria and fungi

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

Isolation of the Bacillus thuringiensis plasmid carrying Bacthuricin F4 coding genes and evidence of its conjugative transfer

INTRODUCTION: Conjugation is an excellent natural mode of DNA transfer in vivo between bacteria, particularly when these conjugative elements carry technological traits such as bacteriocin encoding genes. In the present work, the bacteriocinogenic plasmid pIBF4 from Bacillus thuringiensis responsible of Bacthuricin F4 synthesis was isolated and characterized. METHODOLOGY: To isolate pIBF4, the total plasmid DNA from a non-bacteriocin transposant carrying the mini-Tn10 spectinomycin selective marker was extracted and used to transform Escherichia coli strain Top10. PIBF4 was extracted from the obtained transformant and then subjected to restriction enzyme analysis. Plasmid curing experiments were conducted to test the stability of pIBF4 at a stringent temperature of 42°C. Conjugative behavior of pIBF4 was assessed by mating experiments using the non-bacteriocin transposant mutant as a donor strain and several Bacillus thuringiensis strains as recipients. RESULTS: The pIBF4 plasmid was isolated and had a molecular weight of 19.1 kb. Ninety-five percent of cells retained the pIBF4 plasmid after 200 generations, demonstrating its high stability. PIBF4 was successfully transferred to Bacillus thuringiensis HD1CryB strain with a transfer frequency of 1x10(-8) transconjugants per donor cell. The study of the recipient host range revealed that pIBF4 is specifically transferable to Bacillus thuringiensis strains with variable transfer frequencies depending on the recipient host strain. CONCLUSION: Our results show that pIBF4 is a 19.1 kb highly stable plasmid transferable by conjugation to Bacillus thuringiensis strains with deferent transfer frequencies.Tunisian Ministry of Higher Education, Scientific Research, and Technolog

Bioactive Secondary Metabolites from a New Terrestrial Streptomyces sp. TN262

During our search for Streptomyces spp. as new producers of bioactive secondary metabolites, the ethyl acetate extract of the new terrestrial Streptomyces isolate TN262 delivered eight antimicrobially active compounds. They were identified as 1-acetyl-β-carboline (1), tryptophol (2), cineromycin B (3), 2,3-dihydrocineromycin B (4), cyclo-(tyrosylprolyl) (5), 3-(hydroxyacetyl)-indole (6), brevianamide F (7), and cis-cyclo-(l-prolyl-l-leucyl) (8). Three further metabolites were detected in the unpolar fractions using GC–MS and tentatively assigned as benzophenone (9), N-butyl-benzenesulfonamide (10), and hexanedioic acid-bis-(2-ethylhexyl) ester (11). This last compound is known as plasticizer derivatives, but it has never been described from natural sources. In this article, we describe the identification of the new Streptomyces sp. isolate TN262 using its cultural characteristics, the nucleotide sequence of the corresponding 16S rRNA gene and the phylogenetic analysis, followed by optimization, large-scale fermentation, isolation of the bioactive constituents, and determination of their structures. The biological activity of compounds (2), (3), (4), and those of the unpolar fractions was addressed as well

Purification and structure elucidation of antifungal and antibacterial activities of a newly isolated Streptomyces sp. strain US80

Abstract A new actinomycete strain designated as US80 producing antimicrobial activities against Gram-positive and Gram-negative bacteria and fungi was isolated from Tunisian oasis soil. Cultural characteristic studies strongly suggested that this strain belongs to the genus Streptomyces. Nucleotide sequence of the 16S rRNA gene (1517 pb) of the Streptomyces sp. strain US80 exhibited high similarity (97-98 %) to other Streptomyces 16S rRNA genes. A similarity of 98 % was obtained with the 16S rRNA gene of Streptomyces roseoflavus, which produces the aminoglycoside antibiotic flavomycin. The study of the influence of different nutritional compounds on the production of bioactive molecules showed that the highest antimicrobial activities were obtained when glucose at 1 % (w/v) was used as the sole carbon source in the presence of magnesium. Extraction of the fermentation broth of the Streptomyces sp. strain US80 and various separation and purification steps led to the isolation of three pure active molecules. The chemical structure of these three compounds, namely irumamycin (1a), X-14952B (1b) and 17-hydroxy-venturicidin A (1c) was established on the basis on their IR, ESI-MS, 1 H and 13 C/APT NMR data and by comparison with reference data from the literature

Venturicidin C, a new 20-membered macrolide produced by Streptomyces sp. TS-2-2

Venturicidin C (1), a new 20-membered macrolide along with the known venturicidins A (2) and B (3) were isolated from the crude extract of the Appalachian bacterial strain Streptomyces sp. TS-2-2. Additionally, nine other known compounds namely nocardamine, dehydroxynocardamine, desmethylenlnocardamine, ferrioxamine E (FOE), adenosine, riboflavin, cyclo(d)-trans-4-OH-Pro-(d)-Phe, cyclo(d)-Pro-(d)-Phe, and N-(2-phenylethyl)-acetamide were also isolated and identified. The structure of the new macrolide 1 was elucidated by the cumulative analyses of NMR and HR-MS spectrometry data. Complete NMR assignments for the known venturicidins A (2) and B (3) are also provided, for the first time, in this report. Venturicidins A-C did not inhibit the proliferation of A549 lung cancer cell lines but all displayed potent antifungal activity