The functional role of S-protein in the chosen probiotic properties of Lactobacillus species

Potencijalne probiotičke bakterije Lactobacillus buchneri 4t1, Lactobacillus paraplantarum SF9B i Lactobacillus sucicola BGG07-28 te probiotički soj Lactobacillus helveticus M92 imaju na svojoj površini S-proteine čija uloga još nije u potpunosti razjašnjena. S obzirom da mnoga probiotička svojstva bakterija ovise o njihovim površinskim karakteristikama, cilj ovog rada je ispitati ulogu S-proteina u odabranim probiotičkim svojstvima: u preživljavanju probiotičkih bakterijskih stanica u gastrointestinalnom traktu, u zaštiti stanica tijekom procesa liofilizacije te u autoagregaciji, kao preduvjetu za uspješnu adheziju probiotičkih bakterijskih stanica na crijevne epitelne stanice, odnosno u koagregaciji s patogenim bakterijama, za njihovu kompetitivnu ekskluziju. Sva su istraživanja provedena na odabranim Lactobacillus sojevima koji na svojoj površini imaju S-proteine te sa istim sojevima kojima su S-proteini prethodno uklonjeni radi istraživvanja funkcije S-proteina u ispitivanim probiotičkim svojstvima. Rezultati su pokazali da S-proteini imaju značajnu zaštitnu ulogu u preživljavanju stanica u simuliranim uvjetima gastrointestinalnog sustava i tijekom liofilizacije, s obzirom na to da je nakon navedenih procesa smrtnost stanica kod kojih su bili prisutni S-proteini bila puno manja nego kod stanica kojima su S-proteini uklonjeni. S-proteini također imaju značajnu ulogu u uspješnoj autoagregaciji ispitivanih sojeva, u njihovoj koagregaciji sa srodnim bakterijama mliječne kiseline, kao i u koagregaciji s patogenom bakterijom Salmonella enterica serovar Typhimurium.Potential probiotic bacteria Lactobacillus buchneri 4t1, Lactobacillus paraplantarum SF9B, Lactobacillus sucicola BGG07-28 and the probiotic strain Lactobacillus helveticus M92 have on their surface the S-protein whose role is not yet fully understood. Since many properties of probiotic bacteria depend on their surface properties, the aim of this thesis is to examine the role of S-protein in selected probiotic properties: the survival of probiotic bacterial cells in the gastrointestinal tract, protection of the cells during lyophilization process and the autoaggregation, as the requirement for successful probiotic bacterial cell adhesion to intestinal epithelial cells, and in coaggregation with pathogenic bacteria, for their competitive exclusion. All the studies were conducted in selected Lactobacillus strains with the S-protein on its surface and with the same strains which are the S-proteins first removed, which allows the observation of S-protein in the probiotic properties. The results showed that S-proteins have an important protective role in cell survival in simulated gastrointestinal conditions and during lyophilization, considering that after the above mentioned process death in cells which S-proteins were present was much lower than in cells in which the S-proteins have been removed. S-proteins also play a significant role in the successful autoaggregation strains tested, in their coaggregation with related lactic acid bacteria, as well as in coaggregation with pathogenic bacteria Salmonella enterica serovar Typhimurium