Streptomyces tunisiensis sp. nov., a novel Streptomyces species with antibacterial activity.

A novel actinomycete strain designated CN-207(T) was isolated from northern Tunisian soil. This strain exhibited potent broad spectrum antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus species and several other Gram-positive and Gram-negative bacteria. Strain CN-207(T) developed greyish aerial mycelium and pale grey substrate mycelium on yeast extract/malt agar. The isolate produced branching vegetative mycelia with sporangiophores bearing sporangia developing at a late stage of growth. The sporangia contained smooth, non-motile spores. Chemotaxonomic characteristics of strain CN-207(T) were typical of the Streptomyces genus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CN-207(T) belonged to the genus Streptomyces, and was most closely related to Streptomyces griseoincarnatus DSM 40274(T), Streptomyces variabilis DSM 40179(T), Streptomyces labedae DSM 41446(T) and Streptomyces erythrogriseus DSM 40116(T). Low DNA-DNA relatedness values were recorded between strain CN-207(T) and its closest phylogenetic neighbours. Strain CN-207(T) was also distinguished from the nearest phylogenetic neighbours using a combination of morphological and phenotypic characteristics. On the basis of its phenotypic and molecular properties, strain CN-207(T) is considered as a novel species of the Streptomyces genus, for which the name Streptomyces tunisiensis sp. nov. is proposed. The type strain is CN-207(T) (=JCM 17589(T) = DSM 42037(T)).

Enhancement of oxytetracycline production after gamma irradiation-induced mutagenesis of Streptomyces rimosus CN08 strain.

Streptomyces rimosus CN08 isolated from Tunisian soil produced 8.6 mg l(-1) of oxytetracycline (OTC) under submerged fermentation (SmF). Attempts were made for enhancing OTC production after irradiation-induced mutagenesis of Streptomyces rimosus CN08 with Co(60)-γ rays. 125 OTC-producing colonies were obtained after screening on kanamycin containing medium. One mutant called Streptomyces rimosus γ-45 whose OTC production increased 19-fold (165 mg l(-1)) versus wild-type strain was selected. γ-45 mutant was used for OTC production under solid-state fermentation (SSF). Wheat bran (WB) was used as solid substrate and process parameters influencing OTC production were optimized. Solid-state fermentation increased the yield of antibiotic production (257 mg g(-1)) when compared with submerged fermentation. Ammonium sulphate as additional nitrogen source enhanced OTC level to 298 mg g(-1). Interestingly, OTC production by γ-45 mutant was insensitive to phosphate which opens the way to high OTC production even in medium containing phosphate necessary for optimal mycelia growth.

Production and optimization of thermophilic alkaline protease in solid-state fermentation by Streptomyces sp. CN902.

The purpose of the present research is to study the production of thermophilic alkaline protease by a local isolate, Streptomyces sp. CN902, under solid state fermentation (SSF). Optimum SSF parameters for enzyme production have been determined. Various locally available agro-industrial residues have been screened individually or as mixtures for alkaline protease production in SSF. The combination of wheat bran (WB) with chopped date stones (CDS) (5:5) proved to be an efficient mixture for protease production as it gave the highest enzyme activity (90.50 U g(-1)) when compared to individual WB (74.50 U g(-1)) or CDS (69.50 U g(-1)) substrates. This mixed solid substrate was used for the production of protease from Streptomyces sp. CN902 under SSF. Maximal protease production (220.50 U g(-1)) was obtained with an initial moisture content of 60%, an inoculum level of 1 x 10(8) (spore g(-1) substrate) when incubated at 45 degrees C for 5 days. Supplementation of WB and CDS mixtures with yeast extract as a nitrogen source further increased protease production to 245.50 U g(-1) under SSF. Our data demonstrated the usefulness of solid-state fermentation in the production of alkaline protease using WB and CDS mixtures as substrate. Moreover, this approach offered significant benefits due to abundant agro-industrial substrate availability and cheaper cost.

Eco1524I, a type II restriction endonuclease: isolation, partial purification, and characterization.

Various strains of Escherichia coli, isolated from different patients, were screened for type II restriction endonuclease activity. In 1 out of 23 patients, a type II restriction endonuclease activity was found. The restriction endonuclease designated Eco1524I was purified to near homogeneity, based on hydroxyapatite and heparin sepharose chromatography. Eco1524I exhibited endonuclease restriction activity in the pH range from 6.0 to 10.0 (maximum level at pH 8.0) and required Mg2+ as divalent cation. The enzyme was stable till temperature 55 degrees C and pH range from 6.0 to 10.0. Eco1524I recognized the sequence 6-bp palindromic 5'AGG downward arrow CCT 3', producing blunt end and is found to be an isoschizomer of Stu I.