Resumo

The quorum sensing (QS) is a mechanism of communication between cells, leading to differential expression of genes in response to changes to the cell population density. Studies have shown that QS regulates a variety of phenotypes, including the biofilm formation, bioluminescence, cell differentiation, competence, motility and expression of virulence genes. N-acyl homoserine lactones (AHLs) are class 1 of autoinducers (AI-1) and, are used by gram-negative bacteria for communication. Some bacteria, such as Salmonella, do not produce AHLs, but are able to detect and respond to AHLs produced by other bacterial species or even synthetic AHLs. In this study, we evaluated the influence of AHLs on the growth and resistance to acid stress of Salmonella enterica sorovar Enteritidis PT4 578 grown in anaerobic conditions. To evaluate the growth, bacterial cells were inoculated into Tryptic Soy Broth (TSB), prepared in anaerobic conditions. AHLs mix composed of 6, 8, 10 and 12 carbons was added to the growth media and the cultures were incubated at 37 °C, for 36 h. As a control, the cells were incubated in the absence of AHL or in the presence of AHL with furanones mix. The growth was determined spectrophotometrically (600 nm) after 2, 7, 24 and 36 h incubation. To evaluate the resistance to acid stress, bacterial cells were inoculated into Luria Bertani (LB) broth prepared with citrate-phosphate buffer and acidified with hydrochloric acid to pH 2.5, 3.5 and 4.5, in anaerobic conditions. AHLs mix was added to the broth and the cultures were incubated at 37 °C, for 4 h. As a control, the cells were incubated in the absence of AHLs. The survival was determined by plating on LB medium after 1, 3 and 4 h incubation. The intracellular and extracellular protein profile was evaluated of cells in LB broth at pH 4.5 after 4 h of incubation on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS PAGE, 16.5 % T). In the conditions evaluated, AHLs did not affect the growth of S. enterica sorovar Enteritidis PT4 578 neither affected the pathogen resistance or adaptation to acid stress. Considering that so far, AHLs have not been linked to a phenotype of great interest in Salmonella, our results added information that possibly AHLs do not protect the cell against acid stress by inducing protective proteins expression, since there was no difference in the intracellular and extracellular protein profile.