Probiotic Characterization of LAB isolated from Sourdough and Different Traditional Dairy Products Using Biochemical, Molecular and Computational Approaches.

The aim of this study was to identify and isolate lactic acid bacteria (LAB) from indigenous sourdough and dairy samples in Iran, and to assess their probiotic properties in vitro. A total of 560 potential LAB isolates were examined, and 87 demonstrated high survival rates in artificial gastrointestinal fluids without hemolytic activity. The selected isolates exhibited significant auto-aggregation (18.35 to 79.42%) and co-aggregation abilities (20.16 to 71.26%). Additionally, the isolates displayed varying degrees of cell surface hydrophobicity (12.32 to 76.24%). Results indicated that 19 LAB isolates had cholesterol assimilation rates exceeding 30%. Moreover, forty strains tested negative for all twelve assessed pathogenic genes and exhibited good adhesion to human intestinal epithelial cells (13.47 to 49.12%). Furthermore, 24 isolates formed strong biofilms, 29 formed moderate biofilms, and 23 formed weak biofilms. Except for isolates ABRIIFBI-8, ABRIIFBI-16, ABRIIFBI-23, ABRIIFBI-43, ABRIIFBI-56, and ABRIIFBI-62, most isolates were capable of producing exopolysaccharides. Consequently, LAB strains naturally occurring in sourdough and traditional dairy samples were suggested as potential probiotic candidates for incorporation into functional foods.

CRISPR-Cas systems and diversity of targeting phages in Lactobacillus johnsonii strains; insights from genome mining approach.

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (CAS) genes make up bacteria's adaptive immune system. These genes protect bacteria from being eaten by bacteriophages. In this study, CRISPR-Cas systems were characterized using a genomic approach. For this purpose, genome sequences of Lactobacillus johnsonii strains were retrieved, and the diversity, occurrence, and evolution of the CRISPR-Cas systems were analyzed. Then, homology analyses of spacer sequences in identified CRISPR arrays were performed to analyze and characterize the diversity of target phages and plasmids. Finally, the evolutionary paths of spaceromes in each subtype of CRISPR arrays were performed using acquisition and deletion events surveyed under the selective pressure of foreign plasmids and phages. Results showed that 138 strains contain valid CRISPR-Cas structures (CRISPR loci together with the Cas genes) in their genomes, which accounted for about 17% of the L. johnsonii studied strains belonging to subtypes II-A, I-E, and I-C. Moreover, results indicated that some specific groups of plasmids were targeted with specific CRISPR array systems. Homology analysis of spacer sequences with phage genomes also revealed that spacers of strains that harbored only CRISPR-Cas subtype-II targeted a greater diversity of foreign phages. In conclusion, the current study indicates that there is great diversity between the CRISPR-Cas systems identified in L. johnsonii strains. Such diverse CRISPR-Cas systems indicate that these systems are naturally active and important in terms of adaptive immunity and evolutionary relationships.