Associação dos exometabólitos na interação entre pseudomonas aeruginosa e escherichia coli em meio aquoso

Abstract

The secretion of metabolites with antimicrobial activity is one of the strategies employed by bacteria in response to negative stimuli promoted during interspecies competition. In its stationary phase Pseudomonas aeruginosa and Escherichia coli can synthesize diffusible exometabolites whose action is to mutually inhibit the exposed cells, ensuring the balance of both populations in a given place. The former may have an advantage due to the production of pyocyanine. However, the excretion of indol and acetate by E. coli can balance this advantage. This study aimed to detect the influence of indol and acetate on the synthesis of pyocyanin and adhesion of P. aeruginosa, as well as the action of pyocyanin on viable E. coli cells, as well as its adhesion. For this purpose, in vitro tests were conducted to determine the Minimum Inhibitory Concentration (MIC), extraction and quantification of pyocyanin and adhesion by the violet crystal method. The synthesis of piocyanin by Pseudomonas aeruginosa was reduced by up to 50% in the presence of indol. On the other hand, no change in pigment production was observed in the presence of acetate, alone or associated with concentrations lower than 0.5 mM, reflecting an increase of more than 20% in piocyanine production. Indol was also effective in reducing the adhesion of Pseudomonas aeruginosa cells compared to control. For the E. coli strains, the MIC of pyocyanin was 37.5 µg/mL, also reducing cell adhesion. It was observed that despite the inhibition having occurred, no exometabolite promoted biocidal effect in the evaluated strains. The results contribute to the understanding of the ecological mechanisms that occur during the competition between these two bacterial species in aqueous medium.