Lactic acid bacteria of Lactobacillus genus are commercially relevant bacteria used also as probiotics. Lactobacilli in probiotic products are often exposed to prolonged stationary phase before they are ingested. In this thesis we focused on survival and metabolic changes and adaptive strategies during stationary phase. Eight strains of Lactobacillus species, two Pediococcus acidilactici strains, one strain of Enterococcus faecalis and one strain of E. coli were used. Majority of strains were able to survive stationary phase in high numbers, when appropriate medium was used. Results showed that survival is strain specific trait. Exposing strains to prolonged stationary phase leaded to changes in ability to grow on a specific sugar and bile sensitivity. Again changes were strain specific and dependent on the time spent in the stationary phase. Activity of β-galactosidase was also studied in this thesis. Boost of enzymes activity was seen in strain E. faecalis S1-17. Sensitivity to clinically relevant antibiotics is important trait of probiotics, therefore we tested whether changes in resistance appear after exposure to prolonged stationary phase. In some cases we noticed increase in antibiotic resistance after exposure to stationary phase. The most prevalent was resistance to kanamycin. We detected growth advantage in stationary phase (GASP) in one out of three tested L. plantarum strains. L. plantarum KR6 displayed weak GASP phenotype in mixed culture experiment with E. coli.
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