Étude de molécules antibiotiques secrétées par des souches appartenant au genre Streptomyces, isolées de Sebkha.

Abstract

In the search for new antibiotics from actinomycetes, investigating extremes habitats enhances the probability of isolating novel producers. In this context, the antibacterial activity of two Streptomyces sp. strains isolated from saltpans's water (Ain Mlila) was revealed. The antimicrobial activities test realized on five different cultural media revealed that both S1 and S2 strains showed antibacterial and antifungal activities, the importance of which varies according to culture medium and the strains tests. These molecules are, also, active against ß-lactamines, sulfamide, tetracycline, vancomycine and cotrimoxazole resistant bacteria. . The phenotypic and phylogenetic studies of the strains show that they represent probably new species. The antibacterial molecules extraction, from solid media, is widely more advantageous than that made from the same liquid media. These bioactive molecules produced in the first day of culture are stable in the high temperatures (until 100°C), and in the light exposition. According to the TLC results, S1 strain produces one type of polar antibacterial molecule, whereas S2 strain produces two types of different polarity. The bioactive molecules contained in these three fractions are purified by preparative and analytical HPLC. Finally, the structural analysis realized by spectroscopic methods showed that S1 strain produces an antibacterial molecule with cephalosporin properties (oganomycine GF) with some disparities, what supposes that it is probably about a new molecule. While the S2 strain produces two antibacterial molecules of different structure, the first one approach many more cephalosporin with a particular structure whereas the second gets closer to the paulomycine but are not identical, what supposes that it is, probably, about new molecules antibiotics in both cases.