SpaCBA sequence instability and its relationship to the adhesion efficiency of Lactobacillus casei group isolates to Caco-2 cells

The ability to adhere to enterocytes is one of the key features of probiotics. This process involves a number of factors, among which the important role of pili was demonstrated. Some Lactobacillus species are confirmed to have heterotrimeric spaCBA type pili. The aim of this study was to identify spaCBA pili in strains of selected Lactobacillus spp. and assess the impact of their presence and sequence polymorphism on the adhesion of these strains to enterocytes. Total 20 bacterial strains of L. rhamnosus, L. casei and L. paracasei were tested. The presence of pilus specific proteins coding genes spaA, spaB and spaC was verified by PCR in order to identify the presence of sequence polymorphism in the genes possibly affecting the structure of the spaCBA pilus. To correlate spaCBA polymorphism to adhesion capability the adhesion assay was carried out using Caco-2 cell line. The effectiveness of the adhesion was measured using a scintillation counter. The Lactobacillus strains analyzed showed the adhesion to Caco-2 enterocytes capability from 0.6% to 19.6%. The presence of spaCBA pili is a factor increasing the adhesion efficiency of Lactobacillus spp. to Caco-2 enterocytes. Lack of these structures on the surface of bacterial cells results in the reduction in adhesion efficiency, indicating its important role in the adhesion process. But not in all cases the correlation between the presence of protein spaCBA structures and adhesion efficiency was observed, what may indicate the important role of other factors in adhesion of analyzed strains to Caco-2 cells.