Abstract

Two Bacillus sp. strains (B₂₉ and B₂₇) isolated from soil in the South of Tunisia were tested for their abilities to produce antimicrobial compounds. Both strains showed antimicrobial activity against Gram-positive and Gram-negative bacteria, yeasts and fungi. The produced compounds were extracted by using four different solvents. The hexane extract allowed to obtain maximum of activity of the strain B₂₉. The activity of the strain B₂₇ was not elucidated by the four solvents used. Bio-autography results of B₂₉ hexane extract revealed presence of different antibiotics and antifungal compounds with different R_f values of 0.3 and 0.76 for antifungal compounds and of 0.12, 0.14, 0.19 and 0.3 for antibiotics. Two active fractions were isolated from the culture broth of the strain B₂₉using semi-preparative HPLC. Partial sequencing of the 16S RDNA gene was used to identify both of Bacillus strains. They may be assigned to new Bacillus species.

Key words: Antimicrobial activity, Bacillus sp., characterization, salt soil, Tunisia.