Etude et caractérisation des phénazines produites par les Pseudomonas fluorescents à pouvoir antagoniste.

Abstract

The secondary metabolites produced by Pseudomonas can be used against pathogenic microorganisms and as a bioremediation tools. The experimental part of this work is a comparative study of four experimental protocols based on the production and characterisation of phenazines in Pseudomonas. In the first protocol presented by Dahah, (2017), a number of 75 rhizospheric Pseudomonas isolates including 20 with antagonist power have been identified. The phenazines were extracted from these isolates by different solvents and characterized by the analytical methods: TLC, spectrophotometry, HPLC. According to the results, the bacterial isolates belong to the group of fluorescent Pseudomonas and the phenazines have a high antimicrobial activity. In the work of Yaqin Xiang et al (2018), the Phenazine extraction and analysis methods are similar to the previous experiment; however the Pseudomonas strains were different. An in vitro confrontation was carried out in order to study the effect and the mechanisms of action of phenazine-1-carboxamide (PCN) on Rhizoctonia solani. Results indicated that 9.0934 μg / mL of PCN inhibited 50% (EC50) of R. solani growth. Microscopic observations showed an inhibition of the mycelial growth of R. solani and a morphological deformation with even a disappearance of several organelles. Cell and mitochondrial walls are targets of PCN. In another experiment carried out by Wei-Liang Kong et al (2020), the strain ST - TJ4 from the rhizosphere of a healthy poplar had a strong antifungal activity against 11 phytopathogenic fungi. Based on the analysis of its 16S rRNA it was identified as Pseudomonas sp. This strain has also been shown to produce siderophores, cellulase and protease and it has genes involved in the synthesis of phenazines. The results of this work also indicate that the ST - TJ4 strain inhibits the mycelial growth of phytopathogenic fungi by volatile and diffusible compounds. The study presented by Jun Myoung Yu et al (2018) on Pseudomonas chlororaphis 30-84 showed production of three phenazine compounds: phenazine-1 carboxylic acid 2-hydroxy-phenazine-1-carboxylic acid and 2 -hydroxy phenazine. The latter inhibits all fungal pathogens in the rhizosphere. The results also indicated that the amount and type of phenzaine produced had an effect on the degree of inhibition and control of fungal diseases.