Adhesion Ability of Selenium-enriched Bifidobacterium longum DD98 to Caco-2 Cell and Preliminary Study on Its Mechanism

In order to study whether there was a difference in the adhesion ability of a new Bifidobacterium strain DD98 (Bifidobacterium longum DD98, DD98) before and after selenium enrichment, bacterial adhesion rate was evaluated by in vitro adhesion model of Caco-2 cells, the auto-aggregation ability and surface hydrophobicity of the bacteria were also determined, Tuf mRNA, as the quantitative expression of bacterial surface protein was detected by real-time fluorescent quantitative PCR. The results showed that selenium-enriched Bifidobacterium longum DD98 (Se-DD98) presented extremely higher adhesive ability to Caco-2 cells than DD98 (p<0.01).The average number of DD98 bacteria adhering to Caco-2 cells was (39.12±17.57) CFU/100 cells, while the number of Se-DD98 was (581.17±62.79) CFU/100 cells. Compared with the DD98, the auto-aggregation ability of Se-DD98 increased slightly, and the surface hydrophobicity increased significantly from 5.12%±0.16% to 20.25%±2.14% (p<0.01).The results of real-time PCR showed that the expression of Tuf protein mRNA on Se-DD98 cells significantly up-regulated after 2 h incubation with Caco-2 cells (p<0.05). It was indicated that the adhesion ability of DD98 after selenium-enriched culture was significantly improved, and the enhancement of adhesion might be related to the change of Tuf protein.