Abstract:
The work aims to isolate, from Saharan soils actinobacteria producing antibiotics against
Escherichia coli. For this purpose, we chose two soil samples taken from a palm grove and from
a reg in the wilaya of Timimoune. By using a chitin medium, with or without the addition of
selective antibiotics, we were able to isolate a large number of actinobacteria. Then, 100 isolates
were selected based on morphological criteria, and after their purification, we obtained only 74.
The test of this number by the cross-streak method against strains of E. coli on ISP2 medium
revealed only 3 isolates with activity against E. coli. These isolates are TR7, TR14 and TP17.
Their morphological study showed the probable belonging of TR7 and TR14 to the genus
Streptomyces while, TP17 to the genus Streptoverticillium. The results of the production kinetics
on liquid medium were negative whereas, these results on solid medium showed maximum
activity in the 2nd day of incubation with an inhibition diameter of 28mm for isolate TR14 and
23mm for isolate TR7. The antibiogram test of the methanolic extract of the solid medium
revealed an inhibition diameter of 8 mm.
