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Method Article

A Method to Assess Bacteriocin Effects on the Gut Microbiota of Mice

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DOI:

10.3791/56053

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July 25th, 2017

* These authors contributed equally

In This Article

Summary

Bacteriocins are believed to play a key role in defining microbial diversity in different ecological niches. Here, we describe an efficient procedure to assess how bacteriocins affect gut microbiota composition in an animal model.

Abstract

Very intriguing questions arise with our advancing knowledge on gut microbiota composition and the relationship with health, particularly relating to the factors that contribute to maintaining the population balance. However, there are limited available methodologies to evaluate these factors. Bacteriocins are antimicrobial peptides produced by many bacteria that may confer a competitive advantage for food acquisition and/or niche establishment. Many probiotic lactic acid bacteria (LAB) strains have great potential to promote human and animal health by preventing the growth of pathogens. They can also be used for immuno-modulation, as they produce bacteriocins. However, the antagonistic activity of bacteriocins is normally determined by laboratory bioassays under well-defined but over-simplified conditions compared to the complex gut environment in humans and animals, where bacteria face multifactorial influences from the host and hundreds of microbial species sharing the same niche. This work describes a complete and efficient procedure to assess the effect of a variety of bacteriocins with different target specificities in a murine system. Changes in the microbiota composition during the bacteriocin treatment are monitored using compositional 16S rDNA sequencing. Our approach uses both the bacteriocin producers and their isogenic non-bacteriocin-producing mutants, the latter giving the ability to distinguish bacteriocin-related from non-bacteriocin-related modifications of the microbiota. The fecal DNA extraction and 16S rDNA sequencing methods are consistent and, together with the bioinformatics, constitute a powerful procedure to find faint changes in the bacterial profiles and to establish correlations, in terms of cholesterol and triglyceride concentration, between bacterial populations and health markers. Our protocol is generic and can thus be used to study other compounds or nutrients with the potential to alter the host microbiota composition, either when studying toxicity or beneficial effects.

Introduction

Bacteriocins are antimicrobial peptides produced by a wide range of bacterial species1,2. These compounds and their producers, especially LAB, have been explored and exploited worldwide for decades for their potential applications in food preservation and medicine3. Several bacteriocins are known to kill important pathogens, including species of Listeria, Enterococcus, Staphylococcus, and Bacillus. Some bacteriocins even have the ability to modulate the immune response4. Many bacteriocins have relatively narrow spectra, a property that is much a....

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Protocol

Care and handling must be carried out at a specialized animal care unit. Procedures described here were approved by the corresponding Ethics Committee of the University of Valencia and local authorities, following the principles of laboratory animal care mandatory by European Union Law and 2010/63/EU and the Spanish Government RD 53/2013 on the protection of animals used for scientific purposes, in order to respect the 3R principle in animal experimentation (Replacement, Reduction, Refinement).

1. Frozen Bacterial Cultures Used to Inoculate Mice

  1. Inoculate individual strains of LAB in 5 mL of brain-heart infusion (BHI) medium and....

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Results

The production of bacteriocins has been considered a positive probiotic feature in LAB, as it was assumed to prevent the growth of opportunistic bacteria and pathogens. The aim of this work was to show the capacity of bacteriocins to modulate gut microbiota populations in a mouse model. For this purpose, a procedure was developed to compare the effect of the intake of bacteriocin-producing strains and their isogenic non-producing strains. The procedure for the inoculation and the time ext.......

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Discussion

The procedure described here has been used to determine whether changes in the microbiota are bound to health or age. Different parts of the protocol are important, but among them, sampling the feces, choosing the DNA fragment to be sequenced and analyzed, and performing the DNA extraction and bioinformatic analysis could certainly be the most critical points. Sampling is crucial because, for ethical reasons, mice should not be stressed and because it is known to change the proportion of bacteria in the gut. Samples must.......

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Disclosures

The authors have nothing to disclose.

Acknowledgements

The authors wish to thank the EEA Grant NILS Science and Sustainability Coordinated Mobility of Researchers (reference 017-ABEL-CM-2013). C.B. and G.P.-M. were supported by the AGL2015-70487-P grant from the Spanish Ministry of Economy and Competitiveness. O.C.O.U. and D.B.D. were supported by a strategic scholarship program for food science research from the Norwegian University of Life Sciences (NMBU) (project 1205051025). We would also like to thank Inmaculada Noguera for her assistance with animal care and sampling and Jesus Dehesa for his help with ensuring the availability of laboratory materials in the animal facility. We also appreciate Professor Lars-Gustav S....

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Balb/c mice (female)HarlanMice should be 6 - 8 weeks of age
Plastic Petri dishThermo Scientific101VR20
Brain-Heart-Infusion brothConda1400.00
European Bacteriological AgarPronadisa1800.00
Agarose D1 Low EEOPronadisa8010.00
1x TAE bufferThermo Scientific15558042
MRS brothDifco288130
PBS tabletsSigmaP4417-100TAB
scaleMettler ToledoPB602-S
sterile forcepsLevantina de Laboratorios S.L.260-3710014
MicrocentrifugeEppendorf5424
CentrifugeHermleZ383K
sodium chlorideAppliChem Panreac121659.1211
Realpure SSS KitReal Life Science Solutions, Durviz, SpainRBME04 (300 ml)
IsopropanolAppliChem Panreac131090.1611
EthanolAppliChem Panreac131086.1214
Qubit fluorometerInvitrogen
Qubit dsDNA HS Assay KitInvitrogenQ32851
AMPure XP beadsBeckman Coulter Genomics, USAA63881 (60 ml)
PerfeCta NGS library quantification kitQuanta BioSciences, Maryland, USA733-2300
MiSeq v3 reagent kitIllumina, San Diego, California, USAMS-102-3003
Primers for 16S rRNA gene amplificationPrimers contain V3-V4 region of bacterial 16S rRNA gene and Illumina overhang adaptors:5’-TCG TCG GCA GCG TCA GAT GTG TAT AAG AGA CAG CCT ACG GGN GGC WGC AG-3’ and 5'-GTC TCG TGG GCT CGG AGA TGT GTA TAA GAG ACA GGA CTA CHV GGG TAT CTA ATC C-3’
Nextera XT Index kitFC-131-1002Indices and Illumina sequencing adaptors
Micropestle for 1.5 mL tubes, Eppendorf / Sigma , Ref.SigmaZ317314-1PAK
Glass beads, 0.1 mm diameterBiospec Products11079-101
NucleoSpin Gel and PCR Clean-up KitMacherey-Nagel740609.25
Omni Bead Ruptor 24Omni International Inc.19-040
mutanolysinSigmaM9901-10KU
lysozymeRoche10837059001
proteinase KRoche3115887001
RNase ASigmaR4875

References

  1. Papagianni, M. Ribosomally synthesized peptides with antimicrobial properties: biosynthesis, structure, function, and applications. Biotechnol Adv. 21 (6), 465-499 (2003).
  2. Gillor, O., Kirkup, B. C., Riley, M. A. Advances in Applied Microbiology. 54

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Tags

Mouse Model16S rDNA SequencingFecal DNA ExtractionIsogenic StrainsBacterial CulturesCFU CountingDrinking Water TreatmentFecal Sample Collection