L’effet des métabolites de Pseudomonas d’origine marine sur Staphylococcus aureus

Abstract

In the present study we chose a bacterium of the genus Pseudomonas, which possesses a genome coding for many metabolites secreted by this bacterium. Since salt stress can stimulate bacteria to improve the quality and quantity of these substances, we have isolated these bacteria from the sea. The isolation was carried out from 3 different samples: sea water, Algae and sand from the bottom of the sea. The results showed that only sand from the sea bottom was rich in fluorescent Pseudomonas. 15 isolates were selected from bacteria cultured on solid King B, all these isolates secrete a greenish yellow fluorescent pigment and exhibit Gram-negative staining and possess catalase and oxidase. An antagonism test between the Pseudomonas isolates and a pathogenic bacterium Staphylococcus aureus allowed selecting a single isolate that inhibited the pathogenic bacterium on King B but not on Muller Hinton medium . This inhibition also appeared around the wells made on King B and filled with the supernatant of a liquid king B culture of this strain. These results indicate that the metabolite which inhibits Staphylococcus aureus may be pyoverdins which have been found in numerous studies inhibiting bacteria and fungi due to their iron acquisition and consequently their depletion of the medium of this element.