title: The effect of temperature and pH gradients on Lactobacillus rhamnosus gene expression of stress-related genes.
abstract: In this study, Lactobacillus rhamnosus, a renowned probiotic, was cultivated in fluctuating environment. Base gradients caused by a pH control in an industrial process and temperature gradients caused by uneven heating were simulated with a scale-down method. A pH gradient was created in a plug flow reactor (PFR). Expression of pH stress-related genes (atpA, aldB, cfa, groEL, hrcA and pstS) were studied as a relative gene expression study using ldhD as a reference gene. Expression measurements were carried out with the TRAC method. The responses of groEL, hrcA and atpA genes to temperature and pH changes were observed. The expression of phosphate uptake system-related pstS gene was induced almost linearly in the chemostat cultivation experiments when the base gradient in the PFR was increased. Correlations between the results from gene expression studies and freeze stability or acid stress survival were studied. However, by measuring the expression of these genes, we were not able to predict eventual freeze stability or survival from the acid stress test.
authors.affiliation: Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, 00076, Aalto, Finland. janne.wallenius@aalto.fi
authors.forename: Janne
authors.initials: J
authors.lastname: Wallenius
authors.forename: Tuomas
authors.initials: T
authors.lastname: Uuksulainen
authors.forename: Kalle
authors.initials: K
authors.lastname: Salonen
authors.forename: Jari
authors.initials: J
authors.lastname: Rautio
authors.forename: Tero
authors.initials: T
authors.lastname: Eerikäinen
mesh_terms: D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D019921:Biotinylation; D004867:Equipment Design; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D052201:Lacticaseibacillus rhamnosus / Q000378:metabolism*; D015345:Oligonucleotide Probes / Q000737:chemistry; D019936:Probiotics; D018892:Proton-Motive Force; D013696:Temperature
chemical_list: D015345:Oligonucleotide Probes