Abstract

A new actinomycete strain designated PP14 was isolated from a Canadian soil sample, by a dilution agar plating method using a chitin-vitamins B medium supplemented with different antibiotics as selective agents. This actinomycete produced antimicrobial substances and exhibited strong antifungal activity against mycotoxigenic fungi includingAspergillus carbonarius (M333) and Penicillium expansum, and also against phytopathogenic fungi such as Fusarium oxysporum f. sp. lini (Foln 3-5) and F. culmorum. In addition, the strain showed strong activity against the yeast Saccharomyces cerevisiae (ATCC 4226). On the other hand, the strain exhibited an interesting antibacterial activity against bacteria including multi-resistant Klebsiella pneumoniae(E40). The highest antimicrobial activities were obtained on ISP2 medium. The n-butanol extract contained three bioactive spots detected on thin layer chromatography (TLC) plates. Strain PP14 was identified by morphological, chemotaxonomic and phylogenetic analyses to the genus Streptomyces. The 16S rRNA gene sequence similarities showed that strain PP14 is closely associated with members of the Streptomyces violaceoruberspecies group (S. violaceoruber, Streptomyces violaceolatus, Streptomyces tricolor,Streptomyces humiferus, Streptomyces coelescens and Streptomyces anthocyanicus). Furthermore, the comparison of physiological characteristics of strain PP14 with the S. violaceoruber species group showed significant differences. Our results showed that strain PP14 represents a distinct phyletic line suggesting a new genomic species.

Key words: Actinomycetes, Streptomyces, antimicrobial compounds, extremophile microorganisms, multi-resistant bacteria, Canadian soil.