Vpliv dolgotrajne stacionarne faze na izbrane bakterije iz rodu Lactobacillus.

Peternel, Tjaša (author), Mandić Mulec, Ines (mentor), Fujs, Štefan (comentor)

Mlečnokislinske bakterije iz rodu Lactobacillus so komercialno pomembne in jih lahko uporabljamo kot probiotike. Laktobacili v probiotičnih pripravkih so pred zaužitjem pogosto dlje časa izpostavljeni stacionarni fazi. Namen naše magistrske naloge je bil proučiti morebitne metabolne spremembe, ki bi nastale tekom podaljšane stacionarne faze. Poleg osmih sevov Lactobacillus, smo uporabili tudi dva seva Pediococcus acidilactici, sev Enterococcus faecalis ter sev E. coli. Ugotovili smo, da večina uporabljenih sevov dobro preživi stacionarno fazo, če se uporabi ustrezno gojišče. Preživetje pa je tudi sevno specifična lastnost. Pri dolgotrajno staranih kulturah smo opazili spremembe v metabolizmu sladkorjev, kot tudi spremembe v občutljivosti na žolč. Razlike so bile vidne tako na nivoju sevov kot tudi na nivoju različno dolgo staranih kultur. V sklopu magistrske naloge smo proučevali tudi aktivnost β-galaktozidaze pri sevih Lactobacillus, Pediococcus in Enterococcus. Do povečanja aktivnosti encima po preživetju stacionarne faze je prišlo samo v enem primeru pri predstavniku E. faecalis. Pomembna lastnost probiotikov je občutljivost na klinično pomembne vrste antibotikov, zato smo proučevali tudi morebitne spremembe v odpornosti po dolgotrajni stacionarni fazi. Opazili smo, da se v nekaj primerih laktobacilom poveča odpornost proti antibiotikom, če so izpostavljeni stresu stacionarne faze. Najpogosteje smo opazili odpornost proti kanamicinu. Prednost v rasti v stacionarni fazi (GASP) smo med proučevanimi tremi sevi zaznali le pri sevu L. plantarum KR6. Opazili smo šibek fenotip GASP ob ko-kultivaciji z bakterijami vrste Escherichia coli.

• Language: Slovenian
• Keywords: mikrobiologija, laktobacili, Lactobacillus plantarum, stacionarna faza rasti
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [T. Peternel]
• Year: 2018
• PID: 20.500.12556/RUL-101817
• UDC: 602.3:579.864:579.67(043.2)
• COBISS.SI-ID: 9007737
• Publication date in RUL: 07.07.2018

PETERNEL, Tjaša, 2018, Vpliv dolgotrajne stacionarne faze na izbrane bakterije iz rodu Lactobacillus. [online]. Master’s thesis. T. Peternel. [Accessed 5 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=101817

Secondary language

• Language: English
• Title: Effect of prolonged stationary phase on selected strains of bacteria Lactobacillus

Abstract

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.

• Keywords: microbiology, lactobacilli, Lactobacillus plantarum, stationary growth phase