Abstract
BackgroundIn vivo imaging of orally administered lactic acid bacteria (LAB) and commensal bacteria in mice is shown to provide information on the spatial and temporal distribution of bacteria in the gastrointestinal tract. The bacteria can be detected and monitored using bioluminescence or near-infrared fluorescence.ResultsFluorescence imaging of bacteria was established by expressing the infrared fluorescent protein IRFP713 in Lactococcus lactis, Lactobacillus plantarum and Escherichia coli. All three bacterial species were monitored in live mice and no major differences in transit time were observed. Bacteria passed through the stomach and small intestine in 1 h and the majority were secreted from the large intestine after 6–8 h. Intestinal localization of bacteria was confirmed by imaging the isolated intestines and culturing the intestinal content. The use of fluorescence tomography for spatial localization of fluorescent bacteria has been established. The expression of an additional infrared fluorescent protein IRFP682 enabled concomitant detection of two bacterial populations in live mice.ConclusionsThe present work provides a methodological basis for future studies of probiotic and theranostic actions of LAB in mouse disease models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0376-4) contains supplementary material, which is available to authorized users.
Highlights
In vivo imaging of orally administered lactic acid bacteria (LAB) and commensal bacteria in mice is shown to provide information on the spatial and temporal distribution of bacteria in the gastrointestinal tract
We report the expression of infrared fluorescent protein (IRFP) in prototype LAB L. lactis and Lb. plantarum, and in prototype commensal/ pathogen bacterium E. coli to monitor and compare the bacteria in vivo in mice by the use of fluorescence
Construction of infrared fluorescent L. lactis, Lb. plantarum and E. coli Irfp713 open reading frame was cloned into different expression vectors for the expression of IRFP713 in different hosts
Summary
In vivo imaging of orally administered lactic acid bacteria (LAB) and commensal bacteria in mice is shown to provide information on the spatial and temporal distribution of bacteria in the gastrointestinal tract. In vivo optical imaging is a non-invasive method for spatial and temporal monitoring of bacteria in live animals. It can provide data on bacterial dissemination in real time and enables better use of lower numbers of experimental animals. Tissue autofluorescence is minimal in the near infrared region between 700 and 1000 nm [5]. This spectral range is covered by organic fluorescent probes [6], they require an appropriate labelling technique and are less suitable for bacteria since they are diluted with cell division. Infrared fluorescent proteins (IFP1.4 [7] and IRFP [8]) with absorption and emission maxima in the near infrared region have recently
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