الملخص

We isolated 47 different bacterial isolates from 13 different soil samples, five of  them showed antifungal activities belonged to Gram positive bacteria  Bacillus subtilis and were designated as B1,B2,B3,B4 and B5 and they were screened to choose the better one whose activity appear to be high against different kinds of plant and human pathogenic fungi which it was the isolate B4. It's activity is due to the production of antifungal compound(s). Also the optimum conditions for the production of the antifungal compound were determined by  growing the antifungal isolate at 28°C for 5 days at pH 7. The crude extract containing the active compound was extracted and tested against different types of pathogenic fungi and showed different values of activities by measuring the inhibition zone and it was found that the fungus Alternaria alternata was the most sensitive. The crude extract is soluble in water and organic solvents  and the activity of the extract was not affected by heat treatment. Thus the isolate B4 and its extract could be used as a potent biological control agent against these pathogenic fungi rather than chemicals which have harmful side effects.