Annual Research & Review in Biology

Aims: This study was assessed to demonstrate the antimicrobial activity in vitro of an identified fluorescent Pseudomonas strain characterized for its capacity to produce phenazine compounds.

Methodology: First Pseudomonas chlororaphis subsp aureofaciens was inoculated on Nutrient Broth supplemented with Yeast Extract (NBY) and with glucose at a final concentration of 2%, after incubation the filtered culture was acidified with HCl to pH 2. The solution was extracted twice with the same volume of ethyl-acetate. The organic supernatants were combined, dried over anhydrous Na₂SO₄, and evaporated to dryness. The crude extract was resuspended in methanol and tested for antimicrobial activity. Antimicrobial activity was determined (i) by disc diffusion technique for bacteria and (ii) using serial dilution technique in soft PDA for fungi. Secondly the antifungal activity of the bacterial strain was tested against several phytopathogenic fungi in dual culture.

Results: The studied strain has an important activity against the phytopathogenic bacteria and fungi tested. Among the tested fungi Fusarium oxysporum f. sp. albedinis is the most sensitive to the actions of this Pseudomonas, where the inhibition rate reached 77.78%. The less sensitive one was Pythium ultimum with a rate of 55.56%. While for pathogenic bacteria only Salmonella enteridis was sensitive to the tested strain.

Conclusion: Pseudomonas chlororaphis subsp aureofaciens showed appreciable antagonistic activity, in vitro, against special forms of Fusarium oxysporum and the tested phytopathogenic bacteria.