Microflore rhizosphérique de quelques Fabacées (légumineuses) endémiques dans les régions de Boussaâda et de Biskra (Algérie)

Abstract

The antimicrobial activity, phytostimulating effect and mechanism of action of rhizobacteria isolated from three endemic legumes in Algeria (Ononis angustissima, Astragalus gombo and Calobota saharae) were evaluated. Phenotypic and genotypic identification of isolates with high antimicrobial activity revealed the strains Brevibacillus brevis GM100, Bacillus clausii GM17, Streptomyces sp. 21, 2A26, 1B10 and 2C34. The sensitivity of the antimicrobial purified extracts from a bacteriocin producing strains B. brevis GM100 and B. clausii GM17 in the presence of different proteases demonstrate their proteinaceous nature. Furthermore, analyses by MALDI TOF/MS, demonstrated that both bacteriocins Bac-GM100 and Bac-GM17, are monomeric proteins with molecular weight of 4375,66 Da and 5158,11 Da, respectively. These two bacteriocins are thermostable, active in pH range from 3 to 10 and have a large specter of activity. The four Streptomyces sp., solubilize phosphate and produce extracellular fungal cell-wall degrading enzymes chitinase and protease, as well as a marked production of acid-β-indoleacetic (AIA).The In vivo results have revealed that the four strains of Streptomyces sp. significantly stimulate growth and reduce the disease incidence caused by Fusarium oxysporium in chickpea (Cicer arietinum L.). These results indicate that the strains of Streptomyces sp., Brevibacillus brevis GM100 and Bacillus clausii GM17 isolated from rhizosphere of Ononis angustissima could be an interesting source of bioactive substances with a high potential for biological control.