Acyl homoserine lactone-based quorum sensing stimulates biofilm formation by Salmonella Enteritidis in anaerobic conditions

Abstract

Quorum sensing regulates a variety of phenotypes in bacteria including the production of virulence factors. Salmonella spp. have quorum sensing systems mediated by three autoinducers (AI-1, AI-2, and AI-3). The AI-1-mediated system is incomplete in that the bacterium relies on the synthesis of signaling molecules by other microorganisms. This study aimed to evaluate the influence of the AI-1 N-dodecanoyl-DL-homoserine lactone (C12-HSL) on the growth, motility, adhesion, and biofilm formation of Salmonella enterica serovar Enteritidis PT4 578 on a polystyrene surface. Experiments were conducted at 37 °C in anaerobic tryptone soy broth supplemented with C12-HSL and/or a mixture of four synthetic furanones, at the concentration of 50 nM each. The planktonic growth, adhesion, swarming, and twitching motility were not altered in the presence of C12-HSL and/or furanones under anaerobic conditions. However, C12-HSL induced biofilm formation after 36 h of cultivation as determined by quantification of biofilm formation, by enumeration of adhered cells to polystyrene coupons, and finally by imaging the presence of multilayered cells on an epifluorescence microscope. When furanones were present in the medium, an antagonistic effect against C12-HSL on the biofilm development was observed. The results demonstrate an induction of biofilm formation in Salmonella Enteritidis by AI-1 under anaerobic conditions. Considering that Salmonella does not produce AI-1 but respond to it, C12-HSL synthesized by other bacterial species could trigger biofilm formation by this pathogen in conditions that are relevant for its pathogenesis.

Effect of Food Residues in Biofilm Formation on Stainless Steel and Polystyrene Surfaces by Salmonella enterica Strains Isolated from Poultry Houses

“…These results highlight the importance of good hygiene and disinfection practices in dairy equipment such as bulk tanks. Quorum-sensing molecules can increase biofilm formation in Salmonella , and this cell mechanism could play an important role for bacterial communication in multispecies biofilms [ 32 , 33 ]. Due to the microbiota composition of raw milk, Salmonella cells can integrate in biofilms formed by other bacterial genera as a response to quorum-sensing molecules produced by other microorganisms and liberated to the milk.…”

N-dodecanoyl-homoserine lactone influences the levels of thiol and proteins related to oxidation-reduction process in Salmonella

“…Inoculum was prepared according to Almeida et al [ 35 , 41 ]. Tryptone soy broth (TSB; Sigma-Aldrich, India) was prepared with CO 2 under O 2 -free conditions, dispensed in anaerobic bottles that were sealed with butyl rubber stoppers and then autoclaved (anaerobic TSB).…”

“…enterica serovar Typhi containing plasmid pRST98, which harbors the virulence gene rck , increased adhesion to HeLa cells after 1 h at 37 °C in the presence of 5% CO 2 gas [ 40 ]. Biofilm formation by Salmonella Enteritidis PT4 578 in polystyrene surface was positively regulated by C12-HSL after 36 h in anaerobiosis, even though no growth changes were observed in planktonic cells [ 34 , 41 ]. Similarly, Bai and Rai [ 42 ] showed that biofilm formation on polystyrene was increased by Salmonella Typhimurium when cultivated with N -butyryl homoserine lactone (C4-HSL) e C6-HSL.…”

Salmonella enterica Optimizes Metabolism After Addition of Acyl-Homoserine Lactone Under Anaerobic Conditions

“…The choice of C12-HSL was based on studies showing its increased effect on biofilm formation by Salmonella compared to other AHLs with shorter carbon chains due to its higher affinity to SdiA. The concentration too was based on those same studies ( Campos-Galvão et al, 2015 , 2016 ; Almeida et al, 2016 , 2017b , 2018 ). The acetonitrile concentration was less than 1% (vol/vol) in the culture medium since according to Michael et al (2001) , this concentration does not exhibit an effect on the growth and response of Salmonella to AHL.…”

“…This could be explained by its higher binding affinity to the SdiA protein when compared to other AHLs through molecular docking studies ( Almeida et al, 2016 ). Besides C12-HSL, other AHLs tested did not influence the growth of Salmonella Enteritidis PT4 578 cultivated in anaerobic Tryptic Soy Broth (TSB) medium at 37°C ( Campos-Galvão et al, 2015 ; Almeida et al, 2017b ). Cultivation of Salmonella Enteritidis PT4 578 in anaerobic TSB medium supplemented with C12-HSL also led to alterations in protein abundance and levels of organic acids associated with the early stationary phase of growth ( Almeida et al, 2017a ).…”