Assessment of stress tolerance acquisition in the heat-tolerant derivative strains of Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus rhamnosus GG.
OBJECTIVE
The purpose of this study was to investigate the heat-shock response at molecular level in Lactobacillus rhamnosus GG, Bifidobacterium animalis subsp. lactis BB-12 and their heat-tolerant derivatives and to characterize the changes that make the derivatives more robust in terms of heat stress.


RESULTS
The study strains were exposed for 2 h to a heat-shock treatment, Bif. animalis subsp. lactis BB-12 and its derivative at 50°C and the Lact. rhamnosus GG and its derivative at 60°C. Protein synthesis before and after heat shock was examined using proteomics and RT-qPCR. The analysis revealed that the regulation of seven proteins in both strain pairs was modified as a response to heat or between the original and the derivative strain. The comparison of wild-type strains and the heat-tolerant derivatives suggests that the acquisition of heat tolerance in the Bif. animalis subsp. lactis BB-12 derivative is due to a slightly increased constitutive level of chaperones, while in Lact. rhamnosus GG derivative, the main reason seems to be a higher ability to induce the production of chaperones.


CONCLUSIONS
This study revealed possible markers of heat tolerance in B. lactis and Lact. rhamnosus strains.


CONCLUSIONS
This study increases our knowledge on how Lactobacillus and Bifidobacterium strains may acquire heat tolerance. These findings may be useful for improving the heat tolerance of existing probiotic strains as well as screening new heat-tolerant strains.
Functional Foods Forum, University of Turku, Turku, Finland; Food Chemistry and Food Development, Department of Biochemistry, University of Turku, Turku, Finland; Department of Microbiology and Biochemistry of Dairy Products, IPLA-CSIC, Villaviciosa, Asturias, Spain.
J
J
Aakko
B
B
Sánchez
M
M
Gueimonde
S
S
Salminen
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001644:Bifidobacterium / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response / Q000235:genetics*; D006358:Hot Temperature; D006801:Humans; D052201:Lacticaseibacillus rhamnosus / Q000235:genetics* / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism; D019936:Probiotics / Q000378:metabolism; D014176:Protein Biosynthesis
D001426:Bacterial Proteins; D018832:Molecular Chaperones
2D-DIGE; Bifidobacterium animalis subsp. lactis BB-12; Lactobacillus rhamnosus 
GG; heat shock; probiotics; proteomics