Use of green fluorescent protein to monitor Lactobacillus in the gastro‐intestinal tract of chicken

Lactobacilli, like other gut commensal bacteria, are well known for their use in industrial food fermentations and for their probiotic properties. However, little is known about the interaction of these microorganisms with the gastro-intestinal epithelia when administered in vivo . To specifically monitor the passage of lactobacilli after oral administration, the gfp gene was cloned downstream from the constitutive l-lactate dehydrogenase promoter ( pldhL ) in the experiment. The recombinant expression vector pLEM415:: gfp was electroporated into different lactobacilli isolated from chicken. Green fluorescent protein (GFP) was expressed successfully in Lactobacillus delbrueckii ssp. lactis D17 (D17-GFP) and Lactobacillus fructosus C2 (C2-GFP). Moreover, oral administration of D17-GFP in chickens allowed us to trace it in the gastro-intestinal tract. Six hours after ingestion, D17-GFP was detectable in all luminal contents (stomach, jejunum, ileum and caecum). At 42 h post-administration the microorganism was present throughout the intestine with maximum concentrations about 105.5 in all intestinal sections. No fluorescent lactobacilli were detected in the spleen or liver of chickens at any time. Using fluorescence microscopy, it became apparent that the D17-GFP were mainly embedded in the mucus, localized close to the epithelial surface of the intestine and scattered in the intestine lamina propria.