In developed countries, consumption of foods rich in live bacteria is becoming more popular, driven by interests for lightly preserved foods like smoked fishes, new fermented products like lacto-fermented vegetables, and food preservation with protective bacteria. Such foods are considered healthy, although the underlying mechanisms are not fully understood, with possible involvement of probiotic delivery, anti-nutrients removal, microbiota modulation, or bacterial metabolite enrichment.

We hypothesize that the benefits of bacteria-enriched foods result from their content of type 1 or type 2 autoinducers (AI-1 & AI-2), signalling molecules used by bacteria for intercellular communication.

We selected, within relevant starters or bioprotective bacteria, bacterial strains that exhibit the highest AI productions (as quantified by mass spectrometry) when grown on milk ultrafiltrate. Using these strains, we generated model foods enriched in AI which in vitro digestibility test and in vivo impact on the composition of the microbiota (metabarcoding) and on the inflammatory state of the intestinal mucosa (RT-qPCR) following 8 days-supplementation of recently weaned rats, have been assessed.

Hafnia alvei CIRM-BIA 1832 and Lactococcus lactis CIRM-BIA 242 exhibited the highest potential for AI production. Both AIs underwent partial degradation during in vitro test (approximately 30% and 70% for AI-1 and AI-2). Feeding AIs enriched food had no significant impact on rat growth nor food consumption. No significant differences were observed in both ileal and colonic microbiota features (alpha and beta diversities indexes, relative abundances of main families and genera). Conversely, AI-1 supplementation resulted in a significant decrease in PON-2 expression (by 8), and increases in that of TNFa (by 4) and IL1b (by 1.7), in the ileal mucosae of rats.

Finally, AI content in food constitutes a possible vector for interaction with the mucosal homeostasis of the host's intestine. The health implications of the proinflammatory changes observed remain to be established.