title: Effect of the gastrointestinal environment on pH homeostasis of Lactobacillus plantarum and Lactobacillus brevis cells as measured by real-time fluorescence ratio-imaging microscopy.
abstract: In the present work, an in vitro model of the gastrointestinal tract (GIT) was developed to obtain real-time observations of the pH homeostasis of single cells of probiotic Lactobacillus spp. strains as a measure of their physiological state. Changes in the intracellular pH (pHi) were determined using fluorescence ratio imaging microscopy (FRIM) for potential probiotic strains of Lactobacillus plantarum UFLA CH3 and Lactobacillus brevis UFLA FFC199. Heterogeneous populations were observed, with pHi values ranging from 6.5 to 7.5, 3.5 to 5.6 and 6.5 to 8.0 or higher during passage of saliva (pH 6.4), gastric (pH 3.5) and intestinal juices (pH 6.4), respectively. When nutrients were added to gastric juice, the isolate L. brevis significantly decreased its pH(i) closer to the extracellular pH (pH(ex)) than in gastric juice without nutrients. This was not the case for L. plantarum. This study is the first to produce an in vitro GIT model enabling real-time monitoring of pH homeostasis of single cells in response to the wide range of pH(ex) of the GIT. Furthermore, it was possible to observe the heterogeneous response of single cells. The technique can be used to determine the survival and physiological conditions of potential probiotics and other microorganisms during passage through the GIT.
authors.affiliation: Department of Biology, Federal University of Lavras, 37.200-000 Lavras, MG, Brazil; Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark. Electronic address: cintialramos@yahoo.com.br.
authors.forename: Cíntia Lacerda
authors.initials: CL
authors.lastname: Ramos
authors.affiliation: Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark.
authors.forename: Line
authors.initials: L
authors.lastname: Thorsen
authors.affiliation: Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark.
authors.forename: Mia
authors.initials: M
authors.lastname: Ryssel
authors.affiliation: Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark.
authors.forename: Dennis S
authors.initials: DS
authors.lastname: Nielsen
authors.affiliation: Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Siegumfeldt
authors.affiliation: Department of Biology, Federal University of Lavras, 37.200-000 Lavras, MG, Brazil.
authors.forename: Rosane Freitas
authors.initials: RF
authors.lastname: Schwan
authors.affiliation: Food Microbiology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark.
authors.forename: Lene
authors.initials: L
authors.lastname: Jespersen
mesh_terms: D003600:Cytosol / Q000737:chemistry*; D005750:Gastric Juice / Q000737:chemistry* / Q000382:microbiology*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D052196:Levilactobacillus brevis / Q000502:physiology*; D048191:Lactiplantibacillus plantarum / Q000187:drug effects* / Q000502:physiology*; D050296:Microbial Viability / Q000187:drug effects; D008856:Microscopy, Fluorescence / Q000379:methods; D061848:Optical Imaging / Q000379:methods
keywords: FRIM; In vitro gastro-intestinal model; Lactobacillus brevis; Lactobacillus plantarum; Probiotic; pH(i)