Characterisation of the cell envelope and adhesive properties of Lactobacillus johnsonii CRL1647, a probiotic from the honeybee gut.

Lactobacillus johnsonii CRL1647 has been studied due to its beneficial effects on Apis mellifera L. bee colonies. In this work, we analyzed the characteristics of its cell envelope and the relationship of this bacterial structure with adhesion. The study revealed that CRL1647 cells did not harbor S-layer proteins, whereas L. acidophilus ATCC4356, used as a positive control, showed a typical S-layer protein band. L. johnsonii CRL1647 hemagglutinated with sheep erythrocytes. Interestingly, the hemagglutination abilities of L. johnsonii CRL1647 were affected by the treatments with proteinase K and sodium metaperiodate. Transmission electron microscopy (TEM) analysis confirmed that L. acidophilus ATCC4356 has S-layer and revealed that the L. johnsonii CRL1647 cell surface was full of prolongations like 'hairs'. These ultra-structures completely disappeared after the treatment with proteinase K. The CRL1647 strain was able to efficiently adhere to intestinal epithelial cells and was phagocyted by macrophages. Both, adhesion and phagocytosis were significantly diminished when CRL1647 cells were pretreated with proteinase K. From these results, it can be inferred that the principal molecules involved in the adherence of L. johnsonii CRL1647 have a glycoprotein structure, differing them from S-layer proteins.