Contribution à l’étude comparative des activités antibactériennes de deux extraits bruts d’antibiotique et de l’huile synthétisés par des Streptomyces sp isolés des sols de la zone Abd-El-Malek Ramadan (Mostaganem)

Abstract

Actinobactéria and more particularly Streptomyces sp, represent an important biological source in the production of bioactive metabolites. These molecules are widely used in various industrial, pharmaceutical and other fields. The present study consists of isolating the actinomycetes from the soil of the Ouillis area (Mostaganem). After purification of the isolates, the screening by the antagonism test were performed of the against the S. aureus and E. coli strains to select the isolates producing the bioactive substances. These isolates were use in the production of two secondary and primary metabolites (Antibiotic and oil). The antibacterial activities of the two crude extracts obtained were tested against the same strains for the determination of CMI and CMB The results show that soil treatment with CaCO3 gives an average colony count of 1.1 × 106 CFU / ml of actinobactéria. The macroscopic and microscopic observations confirm that the eleven isolates exhibit the characteristics of Streptomyces sp, colonies with different diameters of 2 to 5 mm. The form is variable; the vegetative and aerial mycelia are of different colors. The bacteria are Gram positive; their vegetative mycelia have partitioned structures with a limited number of sporangia. Strain antagonism tests show six isolates of approximately 54.54% producing bioactive substances. The results of the physiological and biochemical tests are positive with the exceptions of a few that are negative such as citrate use and catalase of the S6 strain. The kinetics of microbial fermentation revealed several phases (latency, exponential, stationary and decline) Antibiotic yields ranged from 0.01 to 0.56 ± 0.74 g and were very low compared to oils (29.32 ± 14.84 g and 21.02 ± 21.78 g). However, CMI and CMB of the ATB are respectively 0.125 and 0.5 mg / ml for S. aureus and the CMI, CMB of the E. coli present 0.5 mg /ml. The oil had CMI and CMB of 0.25 and 1 mg /ml respectively for S. aureus and 0.5 and 1 mg / ml for E. coli. At the end of this study, the results are important and for a good valorization, they deserve a more detailed study on the different isolates of Streptomyces sp producing and the crude extracts of the ATB and the oil.