Addition of mucin to the growth medium triggers mucus-binding activity in different strains of Lactobacillus reuteri in vitro.

We have examined the ability of a number of Lactobacillus reuteri strains to bind immobilised mucus material. After growth in MRS broth, some strains showed high binding activity towards mucus whilst many strains exhibited a very low binding activity. In order to simulate the intestinal milieu, we grew the bacteria in MRS supplemented with the glycoprotein mucin, the main component of mucus. Growth under these conditions dramatically improved the mucus-binding activity of most strains that initially showed very poor binding when grown in MRS broth. In addition, there was a strong induction of mucus binding in some strains after growth on solid substrate as compared to growth in liquid culture. Protease treatment of bacteria grown in the presence of mucin eliminated the adhesion, suggesting that mucin induces the production of cell surface proteins that possess mucus-binding properties.