| Abstrakt: |
Antagonistic rhizobacteria play an important role in biological control by producing lytic enzymes and antibiotics and then inhibiting the growth of a large number of pathogenic agents. The present work is in a perspective of antagonists' strains exploration among sixty Plant Growth Promoting Rhizobacteria isolated from Rhus tripartita's rhizosphere, characterized in a previous study. Therefore, six bacterial strains are tested: Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Proteus mirabilis, Enterococcus faecalis and Klebsiella pneumoniae. Different techniques were used: direct inoculation of bacterial cultures, diffusion discs impregnated with the supernatant and the use of bioactive substances extracted. The hydrolytic activity of carbohydrates, lipids and proteins of the positives strains was evaluated. In the present study, the antagonism activity proved to be more relevant for bacterial products than for bacterial culture. Moreover, out of the 60 PGPR strains utilized, 12 showed antagonistic potential against Gram positive and negative bacterial strains tested. Furthermore, the majority (66.66%) of the isolates assayed in our experiment were Gram-positive and belonged to Bacillus genera, compared to only 33.33% Gram-negative. The maximum zone inhibition was 20 mm, and the minimum zone inhibition was 12 mm. In the same way, the tested strains could produce at least two hydrolytic enzymes. The antagonistic effect of selected PGPR suggests the possibility of directly including these microorganisms in preventive control program against plant microbial infections or indirectly through the application of active substances as a curative treatment. [ABSTRACT FROM AUTHOR] |
