Abstract
Atypical enteropathogenic Escherichia coli are capable to form biofilm on biotic and abiotic surfaces, regardless of the adherence pattern displayed. Several E. coli mechanisms are regulated by Quorum sensing (QS), including virulence factors and biofilm formation. Quorum sensing is a signaling system that confers bacteria with the ability to respond to chemical molecules known as autoinducers. Suppressor of division inhibitor (SdiA) is a QS receptor present in atypical enteropathogenic E. coli (aEPEC) that detects acyl homoserine lactone (AHL) type autoinducers. However, these bacteria do not encode an AHL synthase, but they are capable of sensing AHL molecules produced by other species, establishing an inter-species bacterial communication. In this study, we performed experiments to evaluate pellicle, ring-like structure and biofilm formation on wild type, sdiA mutants and complemented strains. We also evaluated the transcription of genes involved in different stages of biofilm formation, such as bcsA, csgA, csgD, fliC and fimA. The sdiA mutants were capable of forming thicker biofilm structures and showed increased motility when compared to wild type and complemented strains. Moreover, they also showed denser pellicles and ring-like structures. Quantitative real-time PCR (qRT-PCR) analysis demonstrated increased csgA, csgD and fliC transcription on mutant strains. Biofilm formation, as well as csgD, csgA and fimA transcription decreased on wild type strains by the addition of AHL. These results indicate that SdiA participates on the regulation of these phenotypes in aEPEC and that AHL addition enhances the repressor effect of this receptor on the transcription of biofilm and motility related genes.
Highlights
Enteropathogenic Escherichia coli (EPEC) is a major cause of diarrhea in children in developing countries [1,2]
EPEC can be divided in two groups: typical EPEC and atypical EPEC [3]. tEPEC strains contain the EAF (EPEC adherence factor) plasmid, which is absent in aEPEC [5]
Considering that the SdiA receptor is capable of recognizing acyl homoserine lactone (AHL) molecules and regulate gene transcription of several bacterial species, we evaluated the influence of these molecules on adhesion and biofilm formation by aEPEC ONT:H25 wild type, sdiA mutant and complemented strains
Summary
Enteropathogenic Escherichia coli (EPEC) is a major cause of diarrhea in children in developing countries [1,2]. EPEC produces a characteristic histopathologic lesion known as attaching and effacing (A/E) on the intestinal mucosa [3,4,5,6]. The A/E lesion results from intimate bacterial adherence to the enterocytes, followed by local microvillus effacement and accumulation of polymerized actin of the cytoskeleton underneath adherent bacteria, forming pedestal-like structures [7]. EPEC can be divided in two groups: typical EPEC (tEPEC) and atypical EPEC (aEPEC) [3]. TEPEC strains contain the EAF (EPEC adherence factor) plasmid, which is absent in aEPEC [5]. Recent epidemiological studies indicate that aEPEC is more prevalent than tEPEC in both developed and developing countries [8].
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