Fig. 5

Bifidobacterium longum 105-A adherence to Caco-2 cells and phagocytosis by murine macrophage. 70% confluent monolayers of Caco-2 cells were challenged with B. longum 105-A (a) and its ∆cpsD mutant (b) at MOI = 100, then determined by phase contrast microscopy. No adherent bacterial cell was observed in the wild-type (a) but a lot of adherent bacteria were observed in ∆cpsD mutant (b). The number of attached ∆cpsD cells per Caco-2 cell was 7.8 ± 2.3 (nucleus ± SD). Three slides for each bacterial strain and at least 20 fields per slide were counted. B. longum 105-A phagocytosis by murine macrophage. Semi-confluent RAW 264.7 murine macrophage was challenged with B. longum 105-A (c) and its ∆cpsD mutant (d) for 30 min. Then, the medium was removed and the cells were washed 5 times with PBS and replace to DMEM containing gentamycin (100 µg/ml) and incubate for another 1 h. The coverslips were then washed 3 times with PBS and the cells were fixed with methanol and stained with Giemsa stain. In the wild-type, no bacterial cell was observed both inside and outside of macrophage cell (c) but ∆cpsD mutant was internalized into Raw 264.7 murine macrophage cells (d). The number of internalized bacterial ce1ls per macrophage cell was 4.1 ± 1