Name: isolation and characterization of the natural microbiota of the model nematode caenorhabditis elegans
Uploaded: 2022-08-17T14:10:00
Description: Watch this Scientific Journal Video about Isolation and Characterization of the Natural Microbiota of the Model Nematode Caenorhabditis elegans at JoVE.com

We acknowledge financial support from the German Science Foundation (projects A1.1 and A1.2 of the Collaborative Research Center 1182 on the Origin and Function of Metaorganisms). We thank the members of the Schulenburg lab for their advice and support.

1. Preparation of buffers and media
<ol>
	<li>Prepare S-buffer by adding 5.85 g of NaCl, 1.123 g of K2HPO4, 5.926 g of KH2PO4, and 1 L of deionized H2O to a flask and autoclave for 20 min at 121 &#176;C.</li>
	<li>Prepare a viscous medium by adding S-buffer containing 1.2% (w/v) hydroxymethylcellulose (the substance causing viscosity of the medium), 5 mg/mL cholesterol, 1 mM MgSO4, 1 mM CaCl2, and 0.1% (v/v) acetone. Autoclave...

<ol>
	<li>Schulenburg, H., F&#233;lix, 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=The+natural+biotic+environment+of+Caenorhabditis+elegans.">The natural biotic environment of Caenorhabditis elegans.</a> Genetics. 206 (1), 55-86 (2017).</li><li>Petersen, C., Dirksen, P., Prahl, S., Strathmann, E. A., Schulenburg, 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+prevalence+of+Caenorhabditis+elegans+across+1.5+years+in+selected+North+German+locations:+the+importance+of+substrate+type,+abiotic+parameters,+and+Caenorhabditis+competitors.">The prevalence of Caenorhabditis elegans across 1.5 years in selected North German locations: the importance of substrate type, abiotic parameters, and Caenorhabditis competitors.</a> BMC Ecology. 14 (1), 4 (2014).</li><li>Petersen, C., 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=Travelling+at+a+slug's+pace:+possible+invertebrate+vectors+of+Caenorhabditis+nematodes.">Travelling at a slug's pace: possible invertebrate vectors of Caenorhabditis nematodes.</a> BMC Ecology. 15 (1), 19 (2015).</li><li>Berg, 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=Assembly+of+the+Caenorhabditis+elegans+gut+microbiota+from+diverse+soil+microbial+environments.">Assembly of the Caenorhabditis elegans gut microbiota from diverse soil microbial environments.</a> The ISME Journal. 10 (8), 1998-2009 (2016).</li><li>Samuel, B. S., Rowedder, H., Braendle, C., F&#233;lix, M. -. A., Ruvkun, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Caenorhabditis+elegans+responses+to+bacteria+from+its+natural+habitats.">Caenorhabditis elegans responses to bacteria from its natural habitats.</a> Proceedings of the National Academy of Sciences. 113 (27), 3941-3949 (2016).</li><li>Dirksen, 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=The+native+microbiome+of+the+nematode+Caenorhabditis+elegans:+gateway+to+a+new+host-microbiome+model.">The native microbiome of the nematode Caenorhabditis elegans: gateway to a new host-microbiome model.</a> BMC Biology. 14 (1), 38 (2016).</li><li>Johnke, J., Dirksen, P., Schulenburg, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Community+assembly+of+the+native+C.+elegans+microbiome+is+influenced+by+time,+substrate+and+individual+bacterial+taxa.">Community assembly of the native C. elegans microbiome is influenced by time, substrate and individual bacterial taxa.</a> Environmental Microbiology. 22 (4), 1265-1279 (2020).</li><li>Zhang, F., 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=Caenorhabditis+elegans+as+a+model+for+microbiome+research.">Caenorhabditis elegans as a model for microbiome research.</a> Frontiers in Microbiology. 8, 485 (2017).</li><li>Dirksen, 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=CeMbio+-+The+Caenorhabditis+elegans+microbiome+resource.">CeMbio - The Caenorhabditis elegans microbiome resource.</a> G3 Genes|Genomes|Genetics. 10 (9), 3025-3039 (2020).</li><li>Zimmermann, 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=The+functional+repertoire+contained+within+the+native+microbiota+of+the+model+nematode+Caenorhabditis+elegans.">The functional repertoire contained within the native microbiota of the model nematode Caenorhabditis elegans.</a> The ISME Journal. 14 (1), 26-38 (2019).</li><li>Kissoyan, K. A. B., 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=Exploring+effects+of+C.+elegans+protective+natural+microbiota+on+host+physiology.">Exploring effects of C. elegans protective natural microbiota on host physiology.</a> Frontiers in Cellular and Infection Microbiology. 12, 775728 (2022).</li><li>Zhang, F., 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=Natural+genetic+variation+drives+microbiome+selection+in+the+Caenorhabditis+elegans+gut.">Natural genetic variation drives microbiome selection in the Caenorhabditis elegans gut.</a> Current Biology. 31 (12), 2603-2618 (2021).</li><li>Berg, 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=TGF&#946;/BMP+immune+signaling+affects+abundance+and+function+of+C.+elegans+gut+commensals.">TGF&#946;/BMP immune signaling affects abundance and function of C. elegans gut commensals.</a> Nature Communications. 10 (1), 604 (2019).</li><li>Kissoyan, K. A. B., 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=Natural+C.+elegans+microbiota+protects+against+infection+via+production+of+a+cyclic+lipopeptide+of+the+viscosin+group.">Natural C. elegans microbiota protects against infection via production of a cyclic lipopeptide of the viscosin group.</a> Current Biology. 29 (6), 1030-1037 (2019).</li><li>Watson, E., MacNeil, L. T., Arda, H. E., Zhu, L. J., Walhout, A. J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integration+of+metabolic+and+gene+regulatory+networks+modulates+the+C.+elegans+dietary+response.">Integration of metabolic and gene regulatory networks modulates the C. elegans dietary response.</a> Cell. 153 (1), 253-266 (2013).</li><li>Watson, 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=Interspecies+systems+biology+uncovers+metabolites+affecting+C.+elegans+gene+expression+and+life+history+traits.">Interspecies systems biology uncovers metabolites affecting C. elegans gene expression and life history traits.</a> Cell. 156 (4), 759-770 (2014).</li><li>MacNeil, L. T., Watson, E., Arda, H. E., Zhu, L. J., Walhout, A. J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diet-induced+developmental+acceleration+independent+of+TOR+and+insulin+in+C.+elegans.">Diet-induced developmental acceleration independent of TOR and insulin in C. elegans.</a> Cell. 153 (1), 240-252 (2013).</li><li>O'Donnell, M. P., Fox, B. W., Chao, P. -. H., Schroeder, F. C., Sengupta, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+neurotransmitter+produced+by+gut+bacteria+modulates+host+sensory+behaviour.">A neurotransmitter produced by gut bacteria modulates host sensory behaviour.</a> Nature. 583 (7816), 415-420 (2020).</li><li>Snoek, B. L., 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=A+multi-parent+recombinant+inbred+line+population+of+C.+elegans+allows+identification+of+novel+QTLs+for+complex+life+history+traits.">A multi-parent recombinant inbred line population of C. elegans allows identification of novel QTLs for complex life history traits.</a> BMC Biology. 17 (1), 24 (2019).</li><li>Avery, L., Shtonda, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Food+transport+in+the+C.+elegans+pharynx.">Food transport in the C. elegans pharynx.</a> Journal of Experimental Biology. 206 (14), 2441-2457 (2003).</li><li>Zhang, 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=A+delicate+balance+between+bacterial+iron+and+reactive+oxygen+species+supports+optimal+C.+elegans+development.">A delicate balance between bacterial iron and reactive oxygen species supports optimal C. elegans development.</a> Cell Host &amp; Microbe. 26 (3), 400-411 (2019).</li><li>Petersen, C., 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=Ten+years+of+life+in+compost:+temporal+and+spatial+variation+of+North+German+Caenorhabditis+elegans+populations.">Ten years of life in compost: temporal and spatial variation of North German Caenorhabditis elegans populations.</a> Ecology and Evolution. 5 (16), 3250-3263 (2015).</li><li>F&#233;lix, M. -. A., Duveau, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Population+dynamics+and+habitat+sharing+of+natural+populations+of+Caenorhabditis+elegans+and+C.+briggsae.">Population dynamics and habitat sharing of natural populations of Caenorhabditis elegans and C. briggsae.</a> BMC Biology. 10 (1), 59 (2012).</li><li>Barri&#232;re, A., F&#233;lix, 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=Temporal+dynamics+and+linkage+disequilibrium+in+natural+Caenorhabditis+elegans+populations.">Temporal dynamics and linkage disequilibrium in natural Caenorhabditis elegans populations.</a> Genetics. 176 (2), 999-1011 (2007).</li><li>Dolgin, E. S., F&#233;lix, M. -. A., Cutter, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hakuna+Nematoda:+genetic+and+phenotypic+diversity+in+African+isolates+of+Caenorhabditis+elegans+and+C.+briggsae.">Hakuna Nematoda: genetic and phenotypic diversity in African isolates of Caenorhabditis elegans and C. briggsae.</a> Heredity. 100 (3), 304-315 (2008).</li><li>Douglas, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+animal+models+for+microbiome+research.">Simple animal models for microbiome research.</a> Nature Reviews Microbiology. 17 (12), 764-775 (2019).</li><li>Barri&#232;re, A., F&#233;lix, 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=Isolation+of+C.+elegans+and+related+nematodes.">Isolation of C. elegans and related nematodes.</a> WormBook. , 1-19 (2014).</li><li>Weisburg, W. G., Barns, S. M., Pelletier, D. A., Lane, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=16S+ribosomal+DNA+amplification+for+phylogenetic+study.">16S ribosomal DNA amplification for phylogenetic study.</a> Journal of Bacteriology. 173 (2), 697-703 (1991).</li><li>Brenner, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetics+of+Caenorhabditis+elegans.">The genetics of Caenorhabditis elegans.</a> Genetics. 77 (1), 71-94 (1974).</li><li>Crombie, T. 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=Local+adaptation+and+spatiotemporal+patterns+of+genetic+diversity+revealed+by+repeated+sampling+of+Caenorhabditis+elegans+across+the+Hawaiian+Islands.">Local adaptation and spatiotemporal patterns of genetic diversity revealed by repeated sampling of Caenorhabditis elegans across the Hawaiian Islands.</a> Molecular Ecology. 31 (8), 2327-2347 (2022).</li><li>Haber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolutionary+history+of+Caenorhabditis+elegans+inferred+from+microsatellites:+Evidence+for+spatial+and+temporal+genetic+differentiation+and+the+occurrence+of+outbreeding.">Evolutionary history of Caenorhabditis elegans inferred from microsatellites: Evidence for spatial and temporal genetic differentiation and the occurrence of outbreeding.</a> Molecular Biology and Evolution. 22 (1), 160-173 (2004).</li><li>Watson, 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=Metabolic+network+rewiring+of+propionate+flux+compensates+vitamin+B12+deficiency+in+C.+elegans.">Metabolic network rewiring of propionate flux compensates vitamin B12 deficiency in C. elegans.</a> eLife. 5, 17670 (2016).</li></ol>

The nematode Caenorhabditis elegans is one of the most intensively studied model organisms in biological research. It was introduced by Sydney Brenner in the 1960s, originally for understanding the development and the function of the nervous system29. Since then, C. elegans has become a powerful model for studying fundamental processes across all biological disciplines, including behavioral biology, neurobiology, aging, evolutionary biology, cell biology, developmental biology, a...

In nature, C. elegans is commonly found in rotten plant matter, especially rotten fruits like apples or on compost heaps1. It is also associated with certain invertebrate hosts such as slugs and woodlice2,3. These habitats are rich in microbes, which not only serve as food for the worm, but may also form stable associations with it. Information on the diversity of naturally associated microorganisms was only published in 20164,5,6. Since then, these and only a few more recent studies have revealed that C. elegans is associated with a variety of bacteria and fungi, most commonly including bacteria of the genus Pseudomonas, Enterobacter, Ochrobactrum, Erwinia, Comamonas, Gluconobacter, and several others6,7,8. Several associated bacteria can stably colonize the worm gut, although not all6,9,10,11,12. They are likely to be of key importance for our understanding of C. elegans biology because they can provide nutrition, protect against pathogens and possibly other stressors, and affect central life-history traits such as reproductive rate, development, or behavioral responses.
As an example, naturally associated isolates of the genera Pseudomonas, Ochrobactrum, and also Enterobacter or Gluconobacter can protect the worm from pathogen infection and killing in distinct ways5,6,11,13,14. A specific isolate of the genus Comamonas influences nematode dietary response, development, lifespan, and fertility15,16,17. Providencia bacteria produce the neuromodulator tyramine and thereby modulate host nervous system activity and resulting behavioral responses18. A set of different naturally associated bacteria were demonstrated to affect population growth rate, fertility, and behavioral responses5,6,9,11,19.
To date, the exact diversity and consistency of the native C. elegans microbiota across habitats and geographic locations are not fully understood, and further associations between the worm and microbes from its environment remain to be uncovered. Several previous studies used bacterial strains isolated from some soil environment, natural C. elegans habitats, or from mesocosm experiments (i.e., lab-based environments that recreate natural habitats) with C. elegans laboratory strains4,5,20. Even though these studies obtained new insights into the influence of microbes on specific nematode traits (e.g., nematode metabolism21), the relevance of these interactions for C. elegans biology in nature is unclear. Therefore, this manuscript describes the methods to directly isolate C. elegans from nature and to isolate and subsequently characterize the naturally associated microbes from both single worms and groups of worms. The described methods are an updated and improved version of the procedures used previously for the isolation and characterization of natural C. elegans and its native microbiota2,6,7. Considering that C. elegans is widely found in decomposing plant matter across the globe (especially in rotting fruits, temperate regions, and in autumn)1,2,22,23,24,25, this protocol can be applied by any lab whenever there is interest in relating C. elegans traits to naturally associated microbes and thus a more naturally relevant context. The latter is pivotal for a full understanding of the nematode&#39;s biology because it is known from a diversity of other host systems that the associated microbiota can affect diverse life history characteristics26, an aspect which is currently largely neglected in the multitude of C. elegans studies across almost all life science disciplines.

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			<td>COMSOL</td>
			<td>COMSOL</td>
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			<td>multiphysics simulation software</td>
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isolation and characterization of the natural microbiota of the model nematode caenorhabditis elegans

The nematode Caenorhabditis elegans interacts with a large diversity of microorganisms in nature. In general, C. elegans is commonly found in rotten plant matter, especially rotten fruits like apples or on compost heaps. It is also associated with certain invertebrate hosts such as slugs and woodlice. These habitats are rich in microbes, which serve as food for C. elegans and which can also persistently colonize the nematode gut. To date, the exact diversity and consistency of the native C. elegans microbiota across habitats and geographic locations is not fully understood. Here, we describe a suitable approach for isolating C. elegans from nature and characterizing the microbiota of worms. Nematodes can be easily isolated from compost material, rotting apples, slugs, or attracted by placing apples on compost heaps. The prime time for finding C. elegans in the Northern Hemisphere is from September until November. Worms can be washed out of collected substrate material by immersing the substrate in buffer solution, followed by the collection of nematodes and their transfer onto nematode growth medium or PCR buffer for subsequent analysis. We further illustrate how the samples can be used to isolate and purify the worm-associated microorganisms and to process worms for 16S ribosomal RNA analysis of microbiota community composition. Overall, the described methods may stimulate new research on the characterization of the C. elegans microbiota across habitats and geographic locations, thereby helping to obtain a comprehensive understanding of the diversity and stability of the nematode's microbiota as a basis for future functional research.

The nematode C. elegans is frequently found in decomposing fruits, such as apples, and also compost samples. In Northern Germany, C. elegans as well as congeneric species (particularly C. remanei but also C. briggsae) are mainly found from September until November2. The nematodes are most commonly found in decomposing plant matter, especially rotting fruits such as apples or pears, and also compost, particularly material that shows a high grade of decomposition....

Watch this Scientific Journal Video about Isolation and Characterization of the Natural Microbiota of the Model Nematode Caenorhabditis elegans at JoVE.com

Isolation and Characterization of the Natural Microbiota of the Model Nematode Caenorhabditis elegans

Caenorhabditis elegans is one of the main model species in biology, yet almost all research is performed in the absence of its naturally associated microbes. The methods described here will help to improve our understanding of the diversity of associated microbes as a basis for future functional C. elegans research.

Isolation and Characterization of the Natural Microbiota of the Model Nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans interacts with a large diversity of microorganisms in nature. In general, C. elegans is commonly found in rotten plant ...

This protocol allows new insights into the natural microbiota of C.elegans. Simultaneously, the isolated microbes can be used in controlled laboratory experiments to characterize microbiota-host interactions and C.elegans biology. This protocol focuses on isolating microbes associated with C.elegans in nature, which are therefore key for understanding the biology of this important model host in a more natural context.It will be helpful to be familiar with the appearance of Caenorhabditis compared to other nematodes. Pipetting under the dissecting scope can initially be challenging, but practice will be helpful. Begin by collecting the environmental samples like compost or rotten fruits in separate plastic bags, tubes, or clean containers.Evenly spread the pieces of the collected environmental samples in a sterile nine centimeter empty Petri dish and add approximately 20 milliliters of sterile viscous medium to cover the sample with the medium. Under the dissecting microscope, search for Caenorhabditis nematodes following the guidelines on isolating Caenorhabditis elegans and related nematodes. Using a 20 to 100 microliter pipette, collect the smallest possible amount of liquid containing the Caenorhabditis nematodes from the plate and transfer it to the three centimeter Petri dish containing one to three milliliters of sterile M9T.To establish a worm population, the individual worms can be transferred onto a plate with a nematode growth medium or NGM. To wash the nematodes and remove the microbes present outside the nematodes, incubate them in M9T for 10 to 15 minutes. Pipette out the smallest possible amount of liquid containing the nematodes and transfer it to a new sterile three centimeter Petri dish containing one to three milliliters of fresh M9T.For unbiased identification of nematode-associated microbes, prepare a 96 well-plate with approximately three sterile beads of one millimeter diameter and add a mixture of 19.5 microliters of PCR buffer and 0.5 microliters of proteinase K per well. Transfer a single washed nematode to each well with as little liquid as possible. Break up the transferred nematodes using a bead homogenizer for three minutes at 30 hertz and centrifuge the plates or tubes at 8, 000 G for 10 seconds at room temperature to get the liquid to the bottom.To identify C.elegans, heat the samples in a PCR cycler for one hour at 50 degrees Celsius and 15 minutes at 95 degrees Celsius to isolate DNA of individual nematodes, or use commercial kits to isolate DNA of worm populations. Freeze the isolated DNA at minus 20 degrees Celsius for long-term storage. Use the DNA and the primer pair NLP 30 forward and NLP 30 reverse and produce a 154 base pair PCR product.To isolate the bacteria, prepare a 96-well plate with approximately three sterile one millimeter beads, 20 microliters of M9 buffer per well, and pipette a single washed nematode to each well with as little liquid as possible. Break up the nematodes as demonstrated before using a bead homogenizer, followed by brief centrifugation of the plate to get the liquid to the bottom. Once done, collect the suspension and serially dilute it at one to 10 proportion.Plate up to 100 microliters of the diluted suspension onto nine centimeter agar plates. Then incubate the plates at 15 to 20 degrees Celsius for 24 to 48 hours. To obtain the pure bacterial culture, pick a single colony from the incubated plate using a sterile loop or toothpick and streak it onto a new agar plate containing the same agar medium used during the purification.Ensure to only use 1/3 of the plate. Then sterilize a reusable loop or use a new sterile loop and drag it through the first streak to create a second streak on another 1/3 part of the sample plate. Repeat it by dragging a loop through the second streak and creating the third streak to achieve the single colony growth.Incubate the plate under the same growth conditions used for isolation, and if required, repeat the purification step. Grow the pure colonies in a liquid medium using the same temperature and growth conditions. Next, characterize the bacteria by extracting the bacterial DNA from pure liquid cultures amplifying the 16S ribosomal RNA using 27 forward and 1495 reverse primers and performing the PCR as described in the text.When the collected fruit and compost samples were distributed in Petri dishes and submerged in a liquid or viscous medium, it resulted in the worms leaving the substrate material and swimming to the medium's surface. The microbes were isolated as pure single colonies and the purification played an essential role as some C.elegans associated bacteria can form biofilms or easily aggregate, resulting in multi-species cultures. The PCR using the C.elegans specific primers, namely NLP 30 forward and NLP 30 reverse, resulted in the amplification of a 154 base pair product for C.elegans.The DNA isolated from single worms resulted in weak PCR bands, whereas DNA extraction from the worm populations consisting of at least 50 worms yielded a larger amount and clearer bands. The success of C.elegans specific PCR was confirmed by running the DNA of a laboratory strain namely N2 as a positive control simultaneously with the DNA of the isolated nematodes Microbes are everywhere. Hence, it is essential to work under sterile conditions to ensure that those microbes that are isolated are truly associated with the worm in nature.The isolated microbes can be used to study host-microbiota interactions or the role of microbes on host biology, for example, aging, development, or immunity in controlled laboratory experiments. Microbes isolated with this technique are currently used by the C.elegans community to improve the understanding of microbiota diversity on host fitness or the role of microbes on immunity.

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Biology

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans

Stable isotopic profiling has long permitted sensitive investigations of the metabolic consequences of genetic mutations and/or pharmacologic therapies in cellular and mammalian models. Here, we describe detailed methods to perform stable isotopic profiling of intermediary metabolism and metabolic flux in the nematode, Caenorhabditis elegans. Methods are described for profiling whole worm free amino acids, labeled carbon dioxide, labeled organic acids, and labeled amino acids in animals exposed to stable isotopes either from early development on nematode growth media agar plates or beginning as young adults while exposed to various pharmacologic treatments in liquid culture. Free amino acids are quantified by high performance liquid chromatography (HPLC) in whole worm aliquots extracted in 4% perchloric acid. Universally labeled 13C-glucose or 1,6-13C2-glucose is utilized as the stable isotopic precursor whose labeled carbon is traced by mass spectrometry in carbon dioxide (both atmospheric and dissolved) as well as in metabolites indicative of flux through glycolysis, pyruvate metabolism, and the tricarboxylic acid cycle. Representative results are included to demonstrate effects of isotope exposure time, various bacterial clearing protocols, and alternative worm disruption methods in wild-type nematodes, as well as the relative extent of isotopic incorporation in mitochondrial complex III mutant worms (isp-1(qm150)) relative to wild-type worms. Application of stable isotopic profiling in living nematodes provides a novel capacity to investigate at the whole animal level real-time metabolic alterations that are caused by individual genetic disorders and/or pharmacologic therapies.

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans

Stable isotopic profiling by gas chromatography mass spectrometric analysis of intermediary metabolic flux is described in the nematode, Caenorhabditis elegans. Methods are detailed for assessing isotopic enrichment in carbon dioxide, organic acids, and amino acids following isotope exposure either during development on agar plates or during adulthood in liquid culture.

Stable isotopic profiling has long permitted sensitive investigations of the metabolic consequences of genetic mutations and/or pharmacologic therapies in ...

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and hermaphrodites. In the earlier phase of gametogenesis, the germ cells of hermaphrodites differentiate into limited number of sperm - around 300 - and are stored in a small 'bag' called the spermatheca. Later on, hermaphrodites continually produce oocytes1. In contrast, males produce exclusively sperm throughout their adulthood. The males produce so much sperm that it accounts for &gt;50% of the total cells in a typical adult worm2. Therefore, isolating sperm from males is easier than from that of hermaphrodites.
Only a small proportion of males are naturally generated due to spontaneous non-disjunction of X chromosome3. Crossing hermaphrodites with males or more conveniently, the introduction of mutations to give rise to Him (High Incidence of Males) phenotype are some of strategies through which one can enrich the male population3.
Males can be easily distinguished from hermaphrodites by observing the tail morphology4. Hermaphrodite's tail is pointed, whereas male tail is rounded with mating structures.
Cutting the tail releases vast number of spermatids stored inside the male reproductive tract. Dissection is performed under a stereo microscope using 27 gauge needles. Since spermatids are not physically connected with any other cells, hydraulic pressure expels internal contents of male body, including spermatids2.
Males are directly dissected on a small drop of 'Sperm Medium'. Spermatids are sensitive to alteration in the pH. Hence, HEPES, a compound with good buffering capacity is used in sperm media. Glucose and other salts present in sperm media help maintain osmotic pressure to maintain the integrity of sperm.
Post-meiotic differentiation of spermatids into spermatozoa is termed spermiogenesis or sperm activation. Shakes5, and Nelson6 previously showed that round spermatids can be induced to differentiate into spermatozoa by adding various activating compounds including Pronase E. Here we demonstrate in vitro spermiogenesis of C. elegans spermatids using Pronase E.
Successful spermiogenesis is pre-requisite for fertility and hence the mutants defective in spermiogenesis are sterile. Hitherto several mutants have been shown to be defective specifically in spermiogenesis process7. Abnormality found during in vitro activation of novel Spe (Spermatogenesis defective) mutants would help us discover additional players participating in this event.

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

A protocol for isolating and activating spermatids from male C. elegans is described here. Cutting the posterior end of male releases spermatids. The spermatids can be activated by addition of protease.

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and ...

Measuring Caenorhabditis elegans Life Span in 96 Well Microtiter Plates

Lifespan is a biological process regulated by several genetic pathways. One strategy to investigate the biology of aging is to study animals that harbor mutations in components of age-regulatory pathways. If these mutations perturb the function of the age-regulatory pathway and therefore alter the lifespan of the entire organism, they provide important mechanistic insights1-3.
Another strategy to investigate the regulation of lifespan is to use small molecules to perturb age-regulatory pathways. To date, a number of molecules are known to extend lifespan in various model organisms and are used as tools to study the biology of aging4-16. The number of molecules identified thus far is small compared to the genetic "toolset" that is available to study the biology of aging.
Caenorhabditis elegans is one of the principle models used to study aging because of its excellent genetics and short lifespan of three weeks. More recently, C.elegans has emerged as a model organism for phenotype based drug screens5,7,16-20 because of its small size and its ability to grow in microtiter plates.
Here we present an assay to measure C.elegans lifespan in 96 well microtiter plates. The assay was developed and successfully used to screen large libraries for molecules that extend C.elegans lifespan7. The reliability of the assay was evaluated in multiple tests: first, by measuring the lifespan of wild type animals grown at different temperatures; second, by measuring the lifespan of mutants with altered lifespans; third, by measuring changes in lifespan in response to different concentrations of the antidepressant Mirtazepine. Mirtazepine has previously been shown to extend lifespan in C.elegans7. The results of these tests show that the assay is able to replicate previous findings from other assays and is quantitative. The microtiter format also makes this lifespan assay compatible with automated liquid handling systems and allows integration into automated platforms.

Measuring Caenorhabditis elegans Life Span in 96 Well Microtiter Plates

In this protocol we present a method to measure Caenorhabditis elegans lifespan in 96 well microtiter plates.

Lifespan is a biological process regulated by several genetic pathways. One strategy to investigate the biology of aging is to study animals that harbor ...

Vampiric Isolation of Extracellular Fluid from Caenorhabditis elegans

The genetically tractable model organism C. elegans has provided insights into a myriad of biological questions, enabled by its short generation time, ease of growth and small size. This small size, though, has disallowed a number of technical approaches found in other model systems. For example, blood transfusions in mammalian systems and grafting techniques in plants enable asking questions of circulatory system composition and signaling. The circulatory system of the worm, the pseudocoelom, has until recently been impossible to assay directly. To answer questions of intercellular signaling and circulatory system composition C. elegans researchers have traditionally turned to genetic analysis, cell/tissue specific rescue, and mosaic analysis. These techniques provide a means to infer what is happening between cells, but are not universally applicable in identification and characterization of extracellular molecules. Here we present a newly developed technique to directly assay the pseudocoelomic fluid of C. elegans. The technique begins with either genetic or physical manipulation to increase the volume of extracellular fluid. Afterward the animals are subjected to a vampiric reverse microinjection technique using a microinjection rig that allows fine balance pressure control. After isolation of extracellular fluid, the collected fluid can be assayed by transfer into other animals or by molecular means. To demonstrate the effectiveness of this technique we present a detailed approach to assay a specific example of extracellular signaling molecules, long dsRNA during a systemic RNAi response. Although characterization of systemic RNAi is a proof of principle example, we see this technique as being adaptable to answer a variety of questions of circulatory system composition and signaling.

Vampiric Isolation of Extracellular Fluid from Caenorhabditis elegans

The model organism C. elegans uses pseudocoelomic fluid as a passive circulatory system. Direct assay of this fluid has not been previously possible. Here we present a novel technique to directly assay the extracellular space, and use systemic silencing signals during an RNAi response as a proof of principle example.

The genetically tractable model organism C. elegans has provided insights into a myriad of biological questions, enabled by its short generation time, ...

Basic Caenorhabditis elegans Methods: Synchronization and Observation

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has since been used extensively as a model organism 1. C. elegans possesses key attributes such as simplicity, transparency and short life cycle that have made it a suitable experimental system for fundamental biological studies for many years 2. Discoveries in this nematode have broad implications because many cellular and molecular processes that control animal development are evolutionary conserved 3.
C. elegans life cycle goes through an embryonic stage and four larval stages before animals reach adulthood. Development can take 2 to 4 days depending on the temperature. In each of the stages several characteristic traits can be observed. The knowledge of its complete cell lineage 4,5 together with the deep annotation of its genome turn this nematode into a great model in fields as diverse as the neurobiology 6, aging 7,8, stem cell biology 9 and germ line biology 10. 
An additional feature that makes C. elegans an attractive model to work with is the possibility of obtaining populations of worms synchronized at a specific stage through a relatively easy protocol. The ease of maintaining and propagating this nematode added to the possibility of synchronization provide a powerful tool to obtain large amounts of worms, which can be used for a wide variety of small or high-throughput experiments such as RNAi screens, microarrays, massive sequencing, immunoblot or in situ hybridization, among others. 
Because of its transparency, C. elegans structures can be distinguished under the microscope using Differential Interference Contrast microscopy, also known as Nomarski microscopy. The use of a fluorescent DNA binder, DAPI (4',6-diamidino-2-phenylindole), for instance, can lead to the specific identification and localization of individual cells, as well as subcellular structures/defects associated to them.

Basic Caenorhabditis elegans Methods: Synchronization and Observation

The easiness of maintaining and propagating the nematode C. elegans make it a nice model organism to work with. The possibility of synchronizing worms allows the work with a significant amount of subjects at the same developmental stage, what facilitates the study of one particular process in many animals.

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has ...

Using RNA-mediated Interference Feeding Strategy to Screen for Genes Involved in Body Size Regulation in the Nematode C. elegans

Double-strand RNA-mediated interference (RNAi) is an effective strategy to knock down target gene expression1-3. It has been applied to many model systems including plants, invertebrates and vertebrates. There are various methods to achieve RNAi in vivo4,5. For example, the target gene may be transformed into an RNAi vector, and then either permanently or transiently transformed into cell lines or primary cells to achieve gene knockdown effects; alternatively synthesized double-strand oligonucleotides from specific target genes (RNAi oligos) may be transiently transformed into cell lines or primary cells to silence target genes; or synthesized double-strand RNA molecules may be microinjected into an organism. Since the nematode C. elegans uses bacteria as a food source, feeding the animals with bacteria expressing double-strand RNA against target genes provides a viable strategy6. Here we present an RNAi feeding method to score body size phenotype. Body size in C. elegans is regulated primarily by the TGF- &beta; - like ligand DBL-1, so this assay is appropriate for identification of TGF-&beta; signaling components7. We used different strains including two RNAi hypersensitive strains to repeat the RNAi feeding experiments. Our results showed that rrf-3 strain gave us the best expected RNAi phenotype. The method is easy to perform, reproducible, and easily quantified. Furthermore, our protocol minimizes the use of specialized equipment, so it is suitable for smaller laboratories or those at predominantly undergraduate institutions.

Using RNA-mediated Interference Feeding Strategy to Screen for Genes Involved in Body Size Regulation in the Nematode C. elegans

We demonstrate how to use the RNAi feeding technique to knock down target genes and score body size phenotype in C. elegans. This method could be used for a large scale screen to identify potential genetic components of interest, such as those involved in body size regulation by DBL-1/TGF-&beta; signaling.

Double-strand RNA-mediated interference (RNAi) is an effective strategy to knock down target gene expression1-3. It has been applied to many model systems ...

Collection, Isolation and Enrichment of Naturally Occurring Magnetotactic Bacteria from the Environment

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of Massachusetts (USA). Since then MTB have been discovered in stratified water- and sediment-columns from all over the world2. One feature common to all MTB is that they contain magnetosomes, which are intracellular, membrane-bound magnetic nanocrystals of magnetite (Fe3O4) and/or greigite (Fe3S4) or both3, 4. In the Northern hemisphere, MTB are typically attracted to the south end of a bar magnet, while in the Southern hemisphere they are usually attracted to the north end of a magnet3,5. This property can be exploited when trying to isolate MTB from environmental samples.
One of the most common ways to enrich MTB is to use a clear plastic container to collect sediment and water from a natural source, such as a freshwater pond. In the Northern hemisphere, the south end of a bar magnet is placed against the outside of the container just above the sediment at the sediment-water interface. After some time, the bacteria can be removed from the inside of the container near the magnet with a pipette and then enriched further by using a capillary racetrack6 and a magnet. Once enriched, the bacteria can be placed on a microscope slide using a hanging drop method and observed in a light microscope or deposited onto a copper grid and observed using transmission electron microscopy (TEM).
Using this method, isolated MTB may be studied microscopically to determine characteristics such as swimming behavior, type and number of flagella, cell morphology of the cells, shape of the magnetic crystals, number of magnetosomes, number of magnetosome chains in each cell, composition of the nanomineral crystals, and presence of intracellular vacuoles.

We demonstrate a method to collect magnetotactic bacteria (MTB) that can be applied to natural waters. MTB can be isolated and enriched from sediment samples using a relatively simple setup that takes advantage of the bacteria's natural magnetism. Isolated MTB can then be examined in detail using both light and electron microscopy.

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Cultivation of Caenorhabditis elegans in Three Dimensions in the Laboratory

The use of genetic model organisms such as Caenorhabditis elegans has led to seminal discoveries in biology over the last five decades. Most of what we know about C. elegans is limited to laboratory cultivation of the nematodes that may not necessarily reflect the environments they normally inhabit in nature. Cultivation of C. elegans in a 3D habitat that is more similar to the 3D matrix that worms encounter in rotten fruits and vegetative compost in nature could reveal novel phenotypes and behaviors not observed in 2D. In addition, experiments in 3D can address how phenotypes we observe in 2D are relevant for the worm in nature. Here, a new method in which C. elegans grows and reproduces normally in three dimensions is presented. Cultivation of C. elegans in Nematode Growth Tube-3D (NGT-3D) can allow us to measure the reproductive fitness of C. elegans strains or different conditions in a 3D environment. We also present a novel method, termed Nematode Growth Bottle-3D (NGB-3D), to cultivate C. elegans in 3D for microscopic analysis. These methods allow scientists to study C. elegans biology in conditions that are more reflective of the environments they encounter in nature. These can help us to understand the overlying evolutionary relevance of the physiology and behavior of C. elegans we observe in the laboratory.

Cultivation of Caenorhabditis elegans in Three Dimensions in the Laboratory

We present a simple method to construct 3D nematode cultivation systems called NGT-3D and NGB-3D. These can be used to study nematode fitness and behaviors in habitats that are more similar to natural Caenorhabditis elegans habitats than the standard 2D laboratory C. elegans culture plates.

The use of genetic model organisms such as Caenorhabditis elegans has led to seminal discoveries in biology over the last five decades. Most of what we ...

Using Caenorhabditis elegans to Screen for Tissue-Specific Chaperone Interactions

Correct folding and assembly of proteins and protein complexes are essential for cellular function. Cells employ quality control pathways that correct, sequester or eliminate damaged proteins to maintain a healthy proteome, thus ensuring cellular proteostasis and preventing further protein damage. Because of redundant functions within the proteostasis network, screening for detectable phenotypes using knockdown or mutations in chaperone-encoding genes in the multicellular organism Caenorhabditis elegans results in the detection of minor or no phenotypes in most cases. We have developed a targeted screening strategy to identify chaperones required for a specific function and thus bridge the gap between phenotype and function. Specifically, we monitor novel chaperone interactions using RNAi synthetic interaction screens, knocking-down chaperone expression, one chaperone at a time, in animals carrying a mutation in a chaperone-encoding gene or over-expressing a chaperone of interest. By disrupting two chaperones that individually present no gross phenotype, we can identify chaperones that aggravate or expose a specific phenotype when both perturbed. We demonstrate that this approach can identify specific sets of chaperones that function together to modulate the folding of a protein or protein complexes associated with a given phenotype.

Using Caenorhabditis elegans to Screen for Tissue-Specific Chaperone Interactions

To study chaperone-chaperone and chaperone-substrate interactions, we perform synthetic interaction screens in Caenorhabditis elegans using RNA interference in combination with mild mutations or over-expression of chaperones and monitor tissue-specific protein dysfunction at the organismal level.

Correct folding and assembly of proteins and protein complexes are essential for cellular function. Cells employ quality control pathways that correct, ...