engleski

The role of S-layer proteins as one of the most abundant biopolymers on Earth in probiotic properties of bacterial strain Lactobacillus brevis SF9B

Surface (S)-layer proteins (Slps) form crystalline arrays of protein subunits as the outermost component of the cell wall in only few strains of Lactobacillus genera. In the genome of Lactobacillus brevis SF9B strain, three regions showed high homology with following slp sequences of the reference strain L. brevis ATCC 14869: with SlpB and SlpC in contig 2 (percentage of identities 65% and 89%, respectively) and with SlpD in contig 32 (percentage of identities 99%). Using SDS-PAGE of GHCl-extracted surface proteins of SF9B, a 50 kDa protein band, indicating the expression of the presumed Slp, was detected. 2D- PAGE of the same protein sample revealed a spot with isoelectric point and molecular weight of approximately 10, and 50 kDa, respectively. Structure and function prediction of the isolated Slp was generated using I-TASSER server, based on the data available for L. brevis ATCC 14869. Since Slps are exposed at the cell surface of certain Lactobacillus strains, they represent an interface between the bacterium and its biotic and abiotic microenvironments. Considering the fact that these environments include stress conditions which can affect bacterial viability and activity in the intestinal tract, Slps must have great importance in probiotic properties of the bacterial cells which express them. Although Slps of Lactobacillus strains are of great research interest for number of years, their physiological function remained poorly understood. However, Slps of strain SF9B mediate bacterial adherence to mucin, Caco-2 cells and extracellular matrix proteins, increase survival of L. brevis SF9B cells in simulated gastrointestinal conditions and during freeze- drying, and enhance their aggregation and coaggregation ability, which are important probiotic properties. The above mentioned results indicate that Slps contribute to technological and probiotic properties of strain L. brevis SF9B and that they have great role in potential application of that strain as novel probiotic culture.

S-layer proteins ; Lactobacillus brevis ; probiotic culture

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