Name: a method to assess bacteriocin effects on the gut microbiota of mice
Uploaded: 2017-07-25T15:00:00
Description: Watch this Scientific Journal Video about A Method to Assess Bacteriocin Effects on the Gut Microbiota of Mice at JoVE.com

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 Snipen for his advice on statistics.

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).
...

<ol>
	<li>Papagianni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomally+synthesized+peptides+with+antimicrobial+properties:+biosynthesis,+structure,+function,+and+applications.">Ribosomally synthesized peptides with antimicrobial properties: biosynthesis, structure, function, and applications.</a> Biotechnol Adv. 21 (6), 465-499 (2003).</li><li>Gillor, O., Kirkup, B. C., Riley, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Advances in Applied Microbiology. 54, 129-146 (2004).</li><li>Dzung, B. D., Ingolf, F. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomally+Synthesized+Antibacterial+Peptides+in+Gram+Positive+Bacteria.">Ribosomally Synthesized Antibacterial Peptides in Gram Positive Bacteria.</a> Curr Drug Targets. 3 (2), 107-122 (2002).</li><li>Dobson, A., Cotter, P. D., Ross, R. P., Hill, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacteriocin+Production:+a+Probiotic+Trait?.">Bacteriocin Production: a Probiotic Trait?.</a> Appl Environ Microb. 78 (1), 1-6 (2012).</li><li>Li, D., Wang, P., Wang, P., Hu, X., Chen, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+gut+microbiota:+A+treasure+for+human+health.">The gut microbiota: A treasure for human health.</a> Biotechnol Adv. 34 (7), 1210-1224 (2016).</li><li>Millette, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capacity+of+Human+Nisin-+and+Pediocin-Producing+Lactic+Acid+Bacteria+To+Reduce+Intestinal+Colonization+by+Vancomycin-Resistant+Enterococci.">Capacity of Human Nisin- and Pediocin-Producing Lactic Acid Bacteria To Reduce Intestinal Colonization by Vancomycin-Resistant Enterococci.</a> Appl Environ Microb. 74 (7), 1997-2003 (2008).</li><li>Cotter, P. D., Ross, R. P., Hill, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacteriocins+[mdash]+a+viable+alternative+to+antibiotics?.">Bacteriocins [mdash] a viable alternative to antibiotics?.</a> Nat Rev Microb. 11 (2), 95-105 (2013).</li><li>Leroy, F., Foulqui&#233; Moreno, M. R., De Vuyst, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enterococcus+faecium+RZS+C5,+an+interesting+bacteriocin+producer+to+be+used+as+a+co-culture+in+food+fermentation.">Enterococcus faecium RZS C5, an interesting bacteriocin producer to be used as a co-culture in food fermentation.</a> Int J Food Microb. 88 (2-3), 235-240 (2003).</li><li>Ananou, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+effect+of+enterocin+AS-48+and+high+hydrostatic+pressure+to+control+food-borne+pathogens+inoculated+in+low+acid+fermented+sausages.">Combined effect of enterocin AS-48 and high hydrostatic pressure to control food-borne pathogens inoculated in low acid fermented sausages.</a> Meat Sci. 84 (4), 594-600 (2010).</li><li>Riboulet-Bisson, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Lactobacillus+salivarius+Bacteriocin+Abp118+on+the+Mouse+and+Pig+Intestinal+Microbiota.">Effect of Lactobacillus salivarius Bacteriocin Abp118 on the Mouse and Pig Intestinal Microbiota.</a> PLoS One. 7 (2), e31113 (2012).</li><li>Charan, J., Kantharia, N. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+calculate+sample+size+in+animal+studies?.">How to calculate sample size in animal studies?.</a> J Pharmacol Pharmacother. 4 (4), 303-306 (2013).</li><li>Umu, &. #. 2. 1. 4. ;. C. O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Potential+of+Class+II+Bacteriocins+to+Modify+Gut+Microbiota+to+Improve+Host+Health.">The Potential of Class II Bacteriocins to Modify Gut Microbiota to Improve Host Health.</a> PLoS One. 11 (10), e0164036 (2016).</li><li>Edgar, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UPARSE:+highly+accurate+OTU+sequences+from+microbial+amplicon+reads.">UPARSE: highly accurate OTU sequences from microbial amplicon reads.</a> Nat Meth. 10 (10), 996-998 (2013).</li><li>Edgar, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+and+clustering+orders+of+magnitude+faster+than+BLAST.">Search and clustering orders of magnitude faster than BLAST.</a> Bioinformatics. 26 (19), 2460-2461 (2010).</li><li>Edgar, R. C., Haas, B. J., Clemente, J. C., Quince, C., Knight, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UCHIME+improves+sensitivity+and+speed+of+chimera+detection.">UCHIME improves sensitivity and speed of chimera detection.</a> Bioinformatics. 27 (16), 2194-2200 (2011).</li><li>Caporaso, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=QIIME+allows+analysis+of+high-throughput+community+sequencing+data.">QIIME allows analysis of high-throughput community sequencing data.</a> Nat Meth. 7 (5), 335-336 (2010).</li><li>DeSantis, T. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Greengenes,+a+Chimera-Checked+16S+rRNA+Gene+Database+and+Workbench+Compatible+with+ARB.">Greengenes, a Chimera-Checked 16S rRNA Gene Database and Workbench Compatible with ARB.</a> Appl Environ Microb. 72 (7), 5069-5072 (2006).</li><li>Caporaso, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PyNAST:+a+flexible+tool+for+aligning+sequences+to+a+template+alignment.">PyNAST: a flexible tool for aligning sequences to a template alignment.</a> Bioinformatics. 26 (2), 266-267 (2010).</li><li>Wang, Q., Garrity, G. M., Tiedje, J. M., Cole, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Naive+Bayesian+Classifier+for+Rapid+Assignment+of+rRNA+Sequences+into+the+New+Bacterial+Taxonomy.">Naive Bayesian Classifier for Rapid Assignment of rRNA Sequences into the New Bacterial Taxonomy.</a> Appl Environ Microb. 73 (16), 5261-5267 (2007).</li><li>Price, M. N., Dehal, P. S., Arkin, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FastTree+2+-+Approximately+Maximum-Likelihood+Trees+for+Large+Alignments.">FastTree 2 - Approximately Maximum-Likelihood Trees for Large Alignments.</a> PLoS One. 5 (3), e9490 (2010).</li><li>Lozupone, C., Knight, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UniFrac:+a+New+Phylogenetic+Method+for+Comparing+Microbial+Communities.">UniFrac: a New Phylogenetic Method for Comparing Microbial Communities.</a> Appl Environ Microb. 71 (12), 8228-8235 (2005).</li><li>Faust, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbial+co-occurrence+relationships+in+the+human+microbiome.">Microbial co-occurrence relationships in the human microbiome.</a> PLoS Comput Biol. 8 (7), e1002606 (2012).</li><li>Shannon, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytoscape:+A+Software+Environment+for+Integrated+Models+of+Biomolecular+Interaction+Networks.">Cytoscape: A Software Environment for Integrated Models of Biomolecular Interaction Networks.</a> Genome Res. 13 (11), 2498-2504 (2003).</li><li>Klindworth, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+general+16S+ribosomal+RNA+gene+PCR+primers+for+classical+and+next-generation+sequencing-based+diversity+studies.">Evaluation of general 16S ribosomal RNA gene PCR primers for classical and next-generation sequencing-based diversity studies.</a> Nucleic Acids Res. 41 (1), e1 (2013).</li><li>Edwards, A. N., Su&#225;rez, J. M., McBride, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culturing+and+Maintaining+Clostridium+difficile+in+an+Anaerobic+Environment.">Culturing and Maintaining Clostridium difficile in an Anaerobic Environment.</a> J Vis Exp. (79), e50787 (2013).</li><li>Delves-Broughton, J., Blackburn, P., Evans, R. J., Hugenholtz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+the+bacteriocin,+nisin.">Applications of the bacteriocin, nisin.</a> Antonie Van Leeuwenhoek. 69 (2), 193-202 (1996).</li><li>Allende, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+and+bacteriocin+production+by+lactic+acid+bacteria+in+vegetable+broth+and+their+effectiveness+at+reducing+Listeria+monocytogenes+in+vitro+and+in+fresh-cut+lettuce.">Growth and bacteriocin production by lactic acid bacteria in vegetable broth and their effectiveness at reducing Listeria monocytogenes in vitro and in fresh-cut lettuce.</a> Food Microb. 24 (7-8), 759-766 (2007).</li><li>Strompfov&#225;, V., Laukov&#225;, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+study+on+bacteriocin+production+of+Enterococci+associated+with+chickens.">In vitro study on bacteriocin production of Enterococci associated with chickens.</a> Anaerobe. 13 (5-6), 228-237 (2007).</li><li>Caballero-Guerrero, B., Jim&#233;nez D&#237;az, R., Maldonado-Barrag&#225;n, A., Ruiz-Barba, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coculture+with+specific+bacteria+enhances+survival+of+Lactobacillus+plantarum+NC8,+an+autoinducer-regulated+bacteriocin+producer,+in+olive+fermentations.">Coculture with specific bacteria enhances survival of Lactobacillus plantarum NC8, an autoinducer-regulated bacteriocin producer, in olive fermentations.</a> Food Microb. 27 (3), 413-417 (2010).</li><li>Drider, D., Fimland, G., H&#233;chard, Y., McMullen, L. M., Pr&#233;vost, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Continuing+Story+of+Class+IIa+Bacteriocins.">The Continuing Story of Class IIa Bacteriocins.</a> Microb. Mol Biol Rev. 70 (2), 564-582 (2006).</li><li>Gao, Y., Jia, S., Gao, Q., Tan, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+bacteriocin+with+a+broad+inhibitory+spectrum+produced+by+Lactobacillus+sake+C2,+isolated+from+traditional+Chinese+fermented+cabbage.">A novel bacteriocin with a broad inhibitory spectrum produced by Lactobacillus sake C2, isolated from traditional Chinese fermented cabbage.</a> Food Control. 21 (1), 76-81 (2010).</li></ol>

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...

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 appreciated in some applications. For example, some narrow-spectrum bacteriocins can be used to direct specific activity against selected groups of problematic bacteria, without much disturbance on the commensal or beneficial flora sharing the same niche; this is especially essential in the gut environment, where numerous beneficial microbes thrive in an interactive and dynamic manner5. Bacteriocins are also very attractive for prophylactic or probiotic use, as they can suppress the (out)growth of pathogens, pathobionts, or opportunistic bacteria that may unbalance the gut homeostasis6,7.
In terms of their nature and physicochemical properties, bacteriocins are very diverse, as they have different structures, target specificities, modes of action, etc. Most bacteriocins have been studied in great detail in in vitro settings, but very few have been tested in food matrices8,9 or in vivo, such as in an animal gut6,10. The in vitro properties can differ to a great extent when assessed in vivo due to the complexity of the gut environment and also to putative unintended effects on beneficial bacteria. Most probiotics are LAB. They produce an array of other metabolites, including short-chain fatty acids, which are known to influence the physiology of the host, as well as to demonstrate antimicrobial properties toward certain bacteria. Therefore, in the case of probiotic strains that produce bacteriocins, it is best to establish realistic assays, such as healthy animals with normal microbiota.
In the present study, we provide a strategy that allows for the assessment of the effect of different bacteriocin-producing strains, whose bacteriocins have different inhibitory spectra, on healthy mice. Our strategy includes feeding mice with isogenic non-bacteriocin mutants, which enables the differentiation of bacteriocin-mediated effects from non-bacteriocin-mediated effects. Sequencing 16S rDNA allows for following the dynamic changes of the bacterial population in the gut. Subsequent statistical analysis deciphers correlations between bacterial species and also between bacterial species and measured physiological parameters (e.g., bodyweight, serum biochemical parameters, etc.). We believe that the protocol presented in this study is also applicable to other probiotic or prebiotic applications beyond the study of bacteriocins in live animals.

<table border="0" cellpadding="0" cellspacing="0" width="826">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Balb/c mice (female)</td>
			<td style="width:141px;">Harlan</td>
			<td style="width:183px;"></td>
			<td style="width:287px;">Mice should be 6 - 8 weeks of age</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Plastic Petri dish</td>
			<td style="width:141px;">Thermo Scientific</td>
			<td style="width:183px;">101VR20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Brain-Heart-Infusion broth</td>
			<td style="width:141px;">Conda</td>
			<td style="width:183px;">1400.00</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">European Bacteriological Agar</td>
			<td style="width:141px;">Pronadisa</td>
			<td style="width:183px;">1800.00</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Agarose D1 Low EEO</td>
			<td style="width:141px;">Pronadisa</td>
			<td style="width:183px;">8010.00</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">1XTAE buffer</td>
			<td style="width:141px;">Thermo Scientific</td>
			<td style="width:183px;">15558042</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MRS broth</td>
			<td style="width:141px;">Difco</td>
			<td style="width:183px;">288130</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PBS tablets</td>
			<td style="width:141px;">Sigma</td>
			<td style="width:183px;">P4417-100TAB</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">scale</td>
			<td style="width:141px;">Mettler Toledo</td>
			<td style="width:183px;">PB602-S</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">sterile forceps</td>
			<td style="width:141px;">Levantina de Laboratorios S.L.</td>
			<td style="width:183px;">260-3710014</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microcentrifuge</td>
			<td style="width:141px;">Eppendorf</td>
			<td style="width:183px;">5424</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge</td>
			<td style="width:141px;">Hermle</td>
			<td style="width:183px;">Z383K</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">sodium chloride</td>
			<td style="width:141px;">AppliChem Panreac</td>
			<td style="width:183px;">121659.1211</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Realpure SSS Kit</td>
			<td style="width:141px;">Real Life Science Solutions, Durviz, Spain</td>
			<td style="width:183px;">RBME04 (300 ml)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Isopropanol</td>
			<td style="width:141px;">AppliChem Panreac</td>
			<td style="width:183px;">131090.1611</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:141px;">AppliChem Panreac</td>
			<td style="width:183px;">131086.1214</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Qubit fluorometer</td>
			<td style="width:141px;">Invitrogen</td>
			<td style="width:183px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Qubit dsDNA HS Assay Kit</td>
			<td style="width:141px;">Invitrogen</td>
			<td style="width:183px;">Q32851</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">AMPure XP beads</td>
			<td style="width:141px;">Beckman Coulter Genomics, USA</td>
			<td style="width:183px;">A63881 (60 ml)</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">PerfeCta NGS library quantification kit</td>
			<td style="width:141px;">Quanta BioSciences, Maryland, USA</td>
			<td style="width:183px;">733-2300</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">MiSeq v3 reagent kit</td>
			<td style="width:141px;">Illumina, San Diego, California, USA</td>
			<td style="width:183px;">MS-102-3003</td>
			<td></td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:216px;">Primers for 16S rRNA gene amplification</td>
			<td style="width:141px;"></td>
			<td style="width:183px;"></td>
			<td style="width:287px;">Primers contain V3-V4 region of bacterial 16S rRNA gene and Illumina overhang adaptors:5&#8217;-TCG TCG GCA GCG TCA GAT GTG TAT AAG AGA CAG CCT ACG GGN GGC WGC AG-3&#8217; and 5&#39;-GTC TCG TGG GCT CGG AGA TGT GTA TAA GAG ACA GGA CTA CHV GGG TAT CTA ATC C-3&#8217;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nextera XT Index kit</td>
			<td style="width:141px;"></td>
			<td style="width:183px;">FC-131-1002</td>
			<td>Indices and Illumina sequencing adaptors</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Micropestle for 1.5 ml tubes, Eppendorf / Sigma , Ref.</td>
			<td style="width:141px;">Sigma</td>
			<td style="width:183px;">Z317314-1PAK</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Glass beads, 0.1 mm diameter</td>
			<td style="width:141px;">Biospec Products</td>
			<td style="width:183px;">11079-101</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">NucleoSpin Gel and PCR Clean-up Kit</td>
			<td style="width:141px;">Macherey-Nagel</td>
			<td style="width:183px;">740609.25</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Omni Bead Ruptor 24</td>
			<td style="width:141px;">Omni International Inc.</td>
			<td style="width:183px;">19-040</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">mutanolysin</td>
			<td style="width:141px;">Sigma</td>
			<td style="width:183px;">M9901-10KU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">lysozyme</td>
			<td style="width:141px;">Roche</td>
			<td style="width:183px;">10837059001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">proteinase K</td>
			<td style="width:141px;">Roche</td>
			<td style="width:183px;">3115887001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rnase A</td>
			<td style="width:141px;">Sigma</td>
			<td style="width:183px;">R4875</td>
			<td></td>
		</tr>
	</tbody>
</table>

a method to assess bacteriocin effects on the gut microbiota of mice

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.

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...

Watch this Scientific Journal Video about A Method to Assess Bacteriocin Effects on the Gut Microbiota of Mice at JoVE.com

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

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.

Very intriguing questions arise with our advancing knowledge on gut microbiota composition and the relationship with health, particularly relating to the ...

The overall goal of this procedure is to assess the influence of bacteriocins on gut microbiota composition using a mouse model. This method will help determine the real effect of bacteriocins from probiotics on the delicate balance of bacterial populations in the gut. The main advantage of this technique is that it allows the analysis of physiological parameters to infer global effects on the host organism.After growing bacterial cultures according to the text protocol, count the cells by first using ice-cold, 0.9%sodium chloride solution to make ten fold serial dilutions. Spread 100 microliters of each dilution onto a BHI Agar plate. Incubate the plates at 30 degrees Celsius overnight for cell growth and colony formation to determine the CFU per milliliter.To prepare bacteria-containing drinking water, use 100 milliliters of sterile, filtered drinking water to dilute the cells from each bacterial stock culture for a final average of ten to the ninth per milliliter CFU. For bacterial survival assessment, count live cells just after dilution and after 24 hours once a week during the first two weeks of bacteria treatment. After ear labeling and acclimating BALB/c young female mice according to the text protocol, on day one of the experiment, collect fecal samples for each mouse and mark them as time zero, or t zero.Place the samples in previously prepared storage boxes and refrigerate the samples at four degrees Celsius until their transport to the laboratory, where they'll be frozen at minus 80 degrees Celsius, then weigh the mice and record the weight. Prepare bacteria-containing drinking water as demonstrated earlier in the video and place drinking water bottles in the corresponding independent cages that are clearly identified so that the mice in each cage share the same water bottle. Prepare new bottles with 100 milliliters of fresh drinking water every day for 15 days preferably using mineral water to avoid chlorine or bacterial inhibiting compounds, and add freshly defrosted bacterial suspensions.Collect fecal samples on days seven and 14. Then, for the next two weeks, allow the mice to drink bacteria-free water and collect additional fecal samples on days 21 and 28. To count bacteriocin-producing bacteria cells in fecal samples, transfer diluted cells of the bacteriocin producer to four milliliters of pre-warmed MRS soft agar.Mix the agar by vortexing and pour the cells onto an MRS 1.5%agar plate. This layer is referred to as the first layer. Transfer another four milliliters of cell-free 0.8%MRS soft agar onto the first layer to embed all the cells within the soft agar.This layer is meant to prevent cells from growing as colonies on the surface of the agar plates. In the sterile hood, dry the plates by taking the lid off for five to 10 minutes before incubating the plates at 30 degrees Celsius for 20 to 24 hours for cell growth and colony formation. To identify bacteriocin producing colonies, mix 40 microliters of an overnight culture of an appropriate indicator strain with four milliliters of pre-warmed soft agar for each plate.Pour the mixture onto the plates. This layer is referred to as the third layer. Dry and incubate the plates as before for cell growth and colony formation.Bacteriocin-producing colonies have clear zones of inhibition around the colonies. Using a commercial DNA extraction kit, suspend one to two fecal mice pellets in 300 microliters of re-suspension solution. Transfer the sample to a two milliliter microtube with 0.5 grams of glass beads.Add one microliter of 10 units per microliter Mutanolysin and two microliters of 20 milligrams per milliliter Lysozyme to each sample and incubate the tubes at 37 degrees Celsius for 40 to 60 minutes. Disrupt the samples using vibration and glass beads, and then proceed with one of the standard protocols for DNA extraction from fecal samples. After isolating and cleaning the DNA according to the text protocol, quantify the samples.Then, normalize and pool each sample from mice sharing the same cage at each time point. The aim of this work was to show the capacity of bacteriocins to modulate gut microbiota populations in a mouse model. The tested bacteriocin-producing lactic acid bacteria, or LAB, as well as the respective counts in drinking water and counts in feces are summarized here.An example of the bacteriocin production by LAB recovered from feces is illustrated in this figure. This PCoA plot reveals that there were no significant differences between the bacteriocin treatments and the isogenic strains when all samples and all bacteria groups were considered together. However, there were likely differences when particular bacterial genera were studied independently, as shown here where changes in the relative abundances of genera were compared to the control group.Furthermore, Pearson's correlation analysis revealed significant linkage between different bacterial genera and a correlation between bacterial genera and triglycerides and LDL in serum, as shown by this network built in CoNet. While attempting this procedure, it's important to remember the use of isogenic strains as controls and a control without bacterial treatment. Following this procedure, other methods like hepatic function, moe-coe-sic transcriptomics, and fecal water metabolomics can be performed and all at once while additional questions, like how do microbiota fluctuations affect the bile salts, cholesterol cycle, digestibility of nutrients, and immune response.

a-method-to-assess-bacteriocin-effects-on-the-gut-microbiota-of-mice

Research

JoVE Journal

Biology

Extracting DNA from the Gut Microbes of the Termite (Zootermopsis Angusticollis) and Visualizing Gut Microbes

Termites are among the few animals known to have the capacity to subsist solely by consuming wood.  The termite gut tract contains a dense and species-rich microbial population that assists in the degradation of lignocellulose predominantly into acetate, the key nutrient fueling termite metabolism (Odelson &amp; Breznak, 1983).  Within these microbial populations are bacteria, methanogenic archaea and, in some ("lower") termites, eukaryotic protozoa. Thus, termites are excellent research subjects for studying the interactions among microbial species and the numerous biochemical functions they perform to the benefit of their host.  The species composition of microbial populations in termite guts as well as key genes involved in various biochemical processes has been explored using molecular techniques (Kudo et al., 1998; Schmit-Wagner et al., 2003; Salmassi &amp; Leadbetter, 2003). These techniques depend on the extraction and purification of high-quality nucleic acids from the termite gut environment.  The extraction technique described in this video is a modified compilation of protocols developed for extraction and purification of nucleic acids from environmental samples (Mor  et al., 1994; Berthelet et al., 1996; Purdy et al., 1996; Salmassi &amp; Leadbetter, 2003; Ottesen et al. 2006) and it produces DNA from termite hindgut material suitable for use as template for polymerase chain reaction (PCR).

Extracting DNA from the Gut Microbes of the Termite Zootermopsis Angusticollis and Visualizing Gut Microbes

This video illustrates the technique for extracting DNA from the species of microbes resident in the termite hindgut. The preparation of a wet mount slide, which is useful for visualizing the gut microbial community is also illustrated, and a tour through the species-rich gut environment is given.

Termites are among the few animals known to have the capacity to subsist solely by consuming wood.  The termite gut tract contains a dense and ...

Creating Defined Gaseous Environments to Study the Effects of Hypoxia on C. elegans

Oxygen is essential for all metazoans to survive, with one known exception1. Decreased O2 availability (hypoxia) can arise during states of disease, normal development or changes in environmental conditions2-5. Understanding the cellular signaling pathways that are involved in the response to hypoxia could provide new insight into treatment strategies for diverse human pathologies, from stroke to cancer. This goal has been impeded, at least in part, by technical difficulties associated with controlled hypoxic exposure in genetically amenable model organisms.
The nematode Caenorhabditis elegans is ideally suited as a model organism for the study of hypoxic response, as it is easy to culture and genetically manipulate. Moreover, it is possible to study cellular responses to specific hypoxic O2 concentrations without confounding effects since C. elegans obtain O2 (and other gasses) by diffusion, as opposed to a facilitated respiratory system6. Factors known to be involved in the response to hypoxia are conserved in C. elegans. The actual response to hypoxia depends on the specific concentration of O2 that is available. In C. elegans, exposure to moderate hypoxia elicits a transcriptional response mediated largely by hif-1, the highly-conserved hypoxia-inducible transcription factor6-9. C .elegans embryos require hif-1 to survive in 5,000-20,000 ppm O27,10. Hypoxia is a general term for "less than normal O2". Normoxia (normal O2) can also be difficult to define. We generally consider room air, which is 210,000 ppm O2 to be normoxia. However, it has been shown that C. elegans has a behavioral preference for O2 concentrations from 5-12% (50,000-120,000 ppm O2)11. In larvae and adults, hif-1 acts to prevent hypoxia-induced diapause in 5,000 ppm O212. However, hif-1 does not play a role in the response to lower concentrations of O2 (anoxia, operational definition &lt;10 ppm O2)13. In anoxia, C. elegans enters into a reversible state of suspended animation in which all microscopically observable activity ceases10. The fact that different physiological responses occur in different conditions highlights the importance of having experimental control over the hypoxic concentration of O2.
Here, we present a method for the construction and implementation of environmental chambers that produce reliable and reproducible hypoxic conditions with defined concentrations of O2. The continual flow method ensures rapid equilibration of the chamber and increases the stability of the system. Additionally, the transparency and accessibility of the chambers allow for direct visualization of animals being exposed to hypoxia. We further demonstrate an effective method of harvesting C. elegans samples rapidly after exposure to hypoxia, which is necessary to observe many of the rapidly-reversed changes that occur in hypoxia10,14. This method provides a basic foundation that can be easily modified for individual laboratory needs, including different model systems and a variety of gasses.

Creating Defined Gaseous Environments to Study the Effects of Hypoxia on C. elegans

This paper details how to use continuous-flow hypoxia chambers to generate atmospheres with defined concentrations of O2 to understand biological responses to decreased O2. This system is easy to setup and maintain, and flexible enough to suit a wide range of O2 concentrations and model systems

Oxygen is essential for all metazoans to survive, with one known exception1. Decreased O2 availability (hypoxia) can arise during states of disease, ...

Method for the Assessment of Effects of a Range of Wavelengths and Intensities of Red/near-infrared Light Therapy on Oxidative Stress In Vitro

Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of central nervous system injuries in vivo, possibly by reducing oxidative stress. However, effects of R/NIR-LT on oxidative stress have been shown to vary depending on wavelength or intensity of irradiation. Studies comparing treatment parameters are lacking, due to absence of commercially available devices that deliver multiple wavelengths or intensities, suitable for high through-put in vitro optimization studies. This protocol describes a technique for delivery of light at a range of wavelengths and intensities to optimize therapeutic doses required for a given injury model. We hypothesized that a method of delivering light, in which wavelength and intensity parameters could easily be altered, could facilitate determination of an optimal dose of R/NIR-LT for reducing reactive oxygen species (ROS) in vitro.
Non-coherent Xenon light was filtered through narrow-band interference filters to deliver varying wavelengths (center wavelengths of 440, 550, 670 and 810nm) and fluences (8.5 x 10-3 to 3.8 x 10-1 J/cm2) of light to cultured cells. Light output from the apparatus was calibrated to emit therapeutically relevant, equal quantal doses of light at each wavelength. Reactive species were detected in glutamate stressed cells treated with the light, using DCFH-DA and H2O2 sensitive fluorescent dyes.&#160;
We successfully delivered light at a range of physiologically and therapeutically relevant wavelengths and intensities, to cultured cells exposed to glutamate as a model of CNS injury. While the fluences of R/NIR-LT used in the current study did not exert an effect on ROS generated by the cultured cells, the method of light delivery is applicable to other systems including isolated mitochondria or more physiologically relevant organotypic slice culture models, and could be used to assess effects on a range of outcome measures of oxidative metabolism.

Method for the Assessment of Effects of a Range of Wavelengths and Intensities of Red/near-infrared Light Therapy on Oxidative Stress In Vitro

Non-coherent Xenon light was passed through narrow-band interference and neutral density filters to deliver light of varying wavelength and intensity to cultured cells. This protocol was used to assess the effects of red/near-infrared light therapy on production of reactive species in vitro: no effects were observed using the tested parameters.

Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of ...

Measurement and Analysis of Extracellular Acid Production to Determine Glycolytic Rate

Extracellular measurement of oxygen consumption and acid production is a simple and powerful way to monitor rates of respiration and glycolysis1. Both mitochondrial (respiration) and non-mitochondrial (other redox) reactions consume oxygen, but these reactions can be easily distinguished by chemical inhibition of mitochondrial respiration. However, while mitochondrial oxygen consumption is an unambiguous and direct measurement of respiration rate2, the same is not true for extracellular acid production and its relationship to glycolytic rate 3-6. Extracellular acid produced by cells is derived from both lactate, produced by anaerobic glycolysis, and CO2, produced in the citric acid cycle during respiration. For glycolysis, the conversion of glucose to lactate- + H+ and the export of products into the assay medium is the source of glycolytic acidification. For respiration, the export of CO2, hydration to H2CO3 and dissociation to HCO3- + H+ is the source of respiratory acidification. The proportions of glycolytic and respiratory acidification depend on the experimental conditions, including cell type and substrate(s) provided, and can range from nearly 100% glycolytic acidification to nearly 100% respiratory acidification 6. Here, we demonstrate the data collection and calculation methods needed to determine respiratory and glycolytic contributions to total extracellular acidification by whole cells in culture using C2C12 myoblast cells as a model.

Glycolysis is a defining metabolic marker in multiple biological systems. Monitoring glycolysis by measuring the extracellular flux of H+ is common, but requires correction to be quantitative and unambiguous. Here, we demonstrate how to gather and correct extracellular flux data to distinguish between respiratory and glycolytic sources of extracellular acidification.

Extracellular measurement of oxygen consumption and acid production is a simple and powerful way to monitor rates of respiration and glycolysis1. Both ...

Gap Junctional Intercellular Communication: A Functional Biomarker to Assess Adverse Effects of Toxicants and Toxins, and Health Benefits of Natural Products

This protocol describes a scalpel loading-fluorescent dye transfer (SL-DT) technique that measures intercellular communication through gap junction channels, which is a major intercellular process by which tissue homeostasis is maintained. Interruption of gap junctional intercellular communication (GJIC) by toxicants, toxins, drugs, etc. has been linked to numerous adverse health effects. Many genetic-based human diseases have been linked to mutations in gap junction genes. The SL-DT technique is a simple functional assay for the simultaneous assessment of GJIC in a large population of cells. The assay involves pre-loading cells with a fluorescent dye by briefly perturbing the cell membrane with a scalpel blade through a population of cells. The fluorescent dye is then allowed to traverse through gap junction channels to neighboring cells for a designated time. The assay is then terminated by the addition of formalin to the cells. The spread of the fluorescent dye through a population of cells is assessed with an epifluorescence microscope and the images are analyzed with any number of morphometric software packages that are available, including free software packages found on the public domain. This assay has also been adapted for in vivo studies using tissue slices from various organs from treated animals. Overall, the SL-DT assay can serve a broad range of in vitro pharmacological and toxicological needs, and can be potentially adapted for high throughput set-up systems with automated fluorescence microscopy imaging and analysis to elucidate more samples in a shorter time.

This protocol describes a scalpel loading-fluorescent dye transfer technique that measures intercellular communication through gap junction channels. Gap junctional intercellular communication is a major cellular process by which tissue homeostasis is maintained and disruption of this cell signaling has adverse health effects.

This protocol describes a scalpel loading-fluorescent dye transfer (SL-DT) technique that measures intercellular communication through gap junction ...

Experimental Approach to Examine Leptin Signaling in the Carotid Bodies and its Effects on Control of Breathing

An adipocyte-produced hormone leptin is a potent respiratory stimulant, which may play an important role in defending respiratory function in obesity. The carotid bodies (CB), a key organ of peripheral hypoxic sensitivity, express the long functional isoform of leptin receptor (LepRb) but the role of leptin signaling in control of breathing has not been fully elucidated. We examined the hypoxic ventilatory response (HVR) (1) in C57BL/6J mice before and after leptin infusion at baseline and after CB denervation; (2) in LepRb-deficient obese db/db mice at baseline and after LepRb overexpression in CBs. In C57BL/6J mice, leptin increased HVR and effects of leptin on HVR were abolished by CB denervation. In db/db mice, LepRb expression in CB augmented the HVR. Therefore, we conclude that leptin acts in CB to augment responses to hypoxia.

Our study focuses on the effects of leptin signaling in carotid body (CB) on the hypoxic ventilatory response (HVR). We performed &#39;loss of function&#39; experiments measuring the effect of leptin on HVR after CB denervation and &#39;gain of function&#39; experiments measuring HVR after overexpression of the leptin receptor in CB.

An adipocyte-produced hormone leptin is a potent respiratory stimulant, which may play an important role in defending respiratory function in obesity. The ...

Divergence of Root Microbiota in Different Habitats based on Weighted Correlation Networks

The root microbiome plays an important role in plant growth and environmental adaptation. Network analysis is an important tool for studying communities, which can effectively explore the interaction relationship or co-occurrence model of different microbial species in different environments. The purpose of this manuscript is to provide details on how to use the weighted correlation network algorithm to analyze different co-occurrence networks that may occur in microbial communities due to different ecological environments. All analysis of the experiment is performed in the WGCNA package. WGCNA is an R package for weighted correlation network analysis. The experimental data used to demonstrate these methods were microbial community data from the NCBI (National Center for Biotechnology Information) database for three niches of the rice (Oryza sativa) root system. We used the weighted correlation network algorithm to construct co-abundance networks of microbial community in each of the three niches. Then, differential co-abundance networks among endosphere, rhizoplane and rhizosphere soil were identified. In addition, the core genera in network were obtained by the "WGCNA" package, which plays an important regulated role in network functions. These methods enable researchers to analyze the response of microbial network to environmental disturbance and verify different microbial ecological response theories. The results of these methods show that the significant differential microbial networks identified in the endosphere, rhizoplane and rhizosphere soil of rice.

Network analysis was applied to evaluate the association of various ecological microbial communities, such as soil, water and rhizosphere. Presented here is a protocol on how to use the WGCNA algorithm to analyze different co-occurrence networks that may occur in the microbial communities due to different ecological environments.

The root microbiome plays an important role in plant growth and environmental adaptation. Network analysis is an important tool for studying communities, ...

Dissection of the Endolymphatic Sac from Mice

The study of mutant mouse models of human hearing and balance disorders has unraveled many structural and functional changes which may contribute to the human phenotypes. Although important progress has been done in the understanding of the development and function of the neurosensory epithelia of the cochlea and vestibula, limited knowledge is available regarding the development, cellular composition, molecular pathways and functional characteristics of the endolymphatic sac. This is, in large part, due to the difficulty of visualizing and microdissecting this tissue, which is an epithelium comprised of only one cell layer. The study presented here describes an approach to access and microdissect the endolymphatic sac from the wild-type mouse inner ear at different ages. The result of a similar dissection is shown in a pendrin-deficient mouse model of enlargement of the vestibular aqueduct. A transgenic mouse with a fluorescent endolymphatic sac is presented. This reporter mouse can be used to readily visualize the endolymphatic sac with limited dissection and determine its size. It can also be used as an educational tool to teach how to dissect the endolymphatic sac. These dissection procedures should facilitate further characterization of this understudied part of the inner ear.

This study describes how to dissect the endolymphatic sac from the inner ear of the mouse at different ages. The result of a similar dissection is shown in an Slc26a4-null mouse model of enlargement of the endolymphatic sac. A transgenic mouse with a fluorescent reporter expressed in the endolymphatic sac is presented as a model to readily visualize the endolymphatic sac, and educational tool.

The study of mutant mouse models of human hearing and balance disorders has unraveled many structural and functional changes which may contribute to the ...

Preparing and Rearing Axenic Insects with Tissue Cultured Seedlings for Host-Gut Microbiota Interaction Studies of the Leaf Beetle

Insect guts are colonized by diverse bacteria that can profoundly impact the host&#39;s physiological traits. Introducing a particular bacterial strain into an axenic insect is a powerful method to verify gut microbial function and elucidate the mechanisms underlying gut microbe-host interactions. Administering antibiotics or sterilizing egg surfaces are two commonly used methods to remove gut bacteria from insects. However, in addition to the potential adverse effects of antibiotics on insects, previous studies indicated that feeding antibiotics could not eliminate gut bacteria. Thus, germ-free artificial diets are generally employed to maintain axenic insects, which is a tedious and labor-intensive process that cannot fully resemble nutritional components in natural food. Described here is an efficient and simple protocol to prepare and maintain axenic larvae of a leaf beetle&#160;(Plagiodera versicolora). Specifically, surfaces of the beetle eggs were sterilized, following which germ-free poplar leaves were used to rear axenic larvae. The axenic status of the insects was further confirmed via culture-dependent and culture-independent assays. Collectively, by combining egg disinfection and germ-free cultivation, an efficient and convenient method was developed to obtain axenic P. versicolora, providing a readily transferable tool for other leaf-eating insects.

To obtain an axenic insect, its egg surface is sterilized, and the hatched larva is subsequently reared using axenic leaves. This method provides an efficient way for axenic insect preparation without administering antibiotics or developing an artificial diet, which can also be applied to other leaf-eating insects.

Insect guts are colonized by diverse bacteria that can profoundly impact the host&#39;s physiological traits. Introducing a particular bacterial strain ...

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice

Mouse models of genetic and acquired risk factors for atrial fibrillation (AF) have proven valuable in investigating the molecular determinants of AF. Programmed electrical stimulation can be performed using transesophageal atrial pacing as a survival procedure, thus enabling serial testing in the same animal. However, numerous pacing protocols exist, which complicates the reproducibility. The present protocol aims to provide a standardized strategy to develop model-specific experimental parameters to improve reproducibility between studies. Preliminary studies are performed to optimize the experimental methods for the specific model under investigation, including age at the time of the study, sex, and parameters of the pacing protocol (e.g., mode of pacing and definition of AF susceptibility). Importantly, care is taken to avoid high stimulus energies, as this can cause stimulation of the ganglionic plexi with inadvertent parasympathetic activation, manifested by exaggerated atrioventricular (AV) block during pacing and often associated with artifactual AF induction. Animals demonstrating this complication must be excluded from the analysis.

The present protocol describes the optimization of experimental parameters when using transesophageal atrial pacing to assess atrial fibrillation susceptibility in mice.

Mouse models of genetic and acquired risk factors for atrial fibrillation (AF) have proven valuable in investigating the molecular determinants of AF. ...