Abstract

Thirty two strains of Aspergillus genus were isolated from soil samples obtained from particular ecosystems: Laghouat endowed with a desert climate and Teleghma with a warm and temperate climate. Based on the morphological aspect, this collection was subdivided into ten phenotypic groups. This identification was confirmed by molecular analyzes using a molecular marker of the genu ribosomal 18s. This marker will allow us to associate our sequences with those of known organisms. In order to discover new antibiotic molecules, the antibacterial activity was performed against two Gram positive bacteria: Staphylococcus aureus and Bacillus subtilis and also two Gram-negative bacteria: Escherichia coli and Pseudomonas aeroginosa, using two different techniques: Agar cylinders and disks technique. The results show that the fungal species have an activity against at least one test bacterium. The Gram positive bacteria were the most affected, where the averages of the inhibition zones reach 34.33 mm. However, Gram-negative bacteria showed less important results from 0 to 12.00 mm. It is recorded that the antibacterial activity was studied for the first time in the following two species: Aspergillus niveus and Aspergillus wentii. Furthermore, an indepth study is underway on bioguided fractionation, which would identify individual components and lead to the isolation of the active ingredient.

Key words: Aspergillus, particular ecosystems, antibacterial activity.