Abstract
Despite having been tagged as safe and beneficial, recent evidence remains inconclusive regarding the status of artificial sweeteners and their putative effects on gut microbiota. Gut microorganisms are essential for the normal metabolic functions of their host. These microorganisms communicate within their community and regulate group behaviors via a molecular system termed quorum sensing (QS). In the present study, we aimed to study the effects of artificial sweeteners on this bacterial communication system. Using biosensor assays, biophysical protein characterization methods, microscale thermophoresis, swarming motility assays, growth assays, as well as molecular docking, we show that aspartame, sucralose, and saccharin have significant inhibitory actions on the Gram-negative bacteria N-acyl homoserine lactone-based (AHL) communication system. Our studies indicate that these three artificial sweeteners are not bactericidal. Protein-ligand docking and interaction profiling, using LasR as a representative participating receptor for AHL, suggest that the artificial sweeteners bind to the ligand-binding pocket of the protein, possibly interfering with the proper housing of the native ligand and thus impeding protein folding. Our findings suggest that these artificial sweeteners may affect the balance of the gut microbial community via QS-inhibition. We, therefore, infer an effect of these artificial sweeteners on numerous molecular events that are at the core of intestinal microbial function, and by extension on the host metabolism.
Highlights
For many years, bacteria have been thought to act independently
To assess the potential of artificial sweeteners to disrupt the acyl homoserine lactone (AHL)-based communication circuit, we used Escherichia coli K802NR, a recombinant bioluminescent reporter strain harboring the plasmid pSB1075 infused with the quorum sensing (QS) promoter lasI that controls the transcription of the V. fischeri luxCDABE and P. aeruginosa lasRI genes
Since athletes pay attention to their diet and use supplements to improve their performance in training sessions and competitions, we hypothesized that they may be the highest consumers of artificial sweeteners, because many of the supplements they use contain artificial sweeteners in an undisclosed amount
Summary
Bacteria have been thought to act independently. The discovery that they act collectively through a sophisticated network of cell-cell communication, known as quorum sensing (QS) has been a great leap in the understanding of bacterial biology [1]. The activated LuxR-type receptors, alter gene expression levels to initiate behaviors that will benefit the group and/or are only achievable as a bacterial community. These include a range of virulence phenotypes such as biofilm formation, protease, and toxin production, and motility mechanisms [7]. Other QS systems identified in bacteria use the signaling molecules known as universal signal autoinducer (AI-2) or autoinducer-3 (AI-3). The latter is produced by intestinal bacterial species including enterohemorrhagic E. coli (EHEC) to regulate its pathogenesis [10]. Follow-up studies confirm a link between 3-oxo-C12:2-HSL and normobiosis [12,13], and an anti-inflammatory effect on enterocytes without interfering with the paracellular permeability [12]
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