Transcriptional analysis of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model.

The aim of the present study was to investigate the transcription of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model. As acidified milk exerted a protective effect on the bacteria leading to increased survival, the gene expression studies were carried out with pre-inoculation of L. acidophilus NCFM in acidified milk. The induction of the genes encoding the stress-related proteins GroEL, DnaK and ClpP, and adhesion-related genes encoding mucin-binding proteins, fibronectin-binding protein and S-layer was analyzed by real-time PCR. The genes encoding GroEL, DnaK and ClpP were significantly up-regulated (9- to 16-fold) during gastric digestion and declined upon subsequent duodenal digestion. The genes encoding mucin-binding proteins and fibronectin-binding protein were not influenced by saliva and gastric juice, but they were significantly upregulated during incubation in duodenal juice and bile (6- to 7-fold). A significant induction of the gene encoding the S-layer protein was not detected. Our results give a better understanding of the functionality of L. acidophilus NCFM and other probiotics during passage through the gastrointestinal tract; hence, they provide an implementable basis for the selection of prospective probiotic candidates.