Name: application of flow vermimetry for quantification and analysis of the caenorhabditis elegans gut microbiome
Uploaded: 2023-03-31T14:20:00
Description: Watch this Scientific Journal Video about Application of Flow Vermimetry for Quantification and Analysis of the Caenorhabditis elegans Gut Microbiome at JoVE.com

This work was supported by NIH grants DP2DK116645 (to B.S.S.), Dunn Foundation pilot award and NASA grant 80NSSC22K0250 (to B.S.S.). This project was also supported by the Cytometry and Cell Sorting Core at Baylor College of Medicine with funding from the CPRIT Core Facility Support Award (CPRIT-RP180672), the NIH (S10 OD025251, CA125123, and RR024574), and the assistance of Joel M. Sederstrom, plus an instrumentation grant for the LPS NIH grant (S10 OD025251). Some strains were provided by the CGC, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440).

1. Preparation of microbiome mixture
<ol>
	<li>Stamp or streak out bacteria from a glycerol freezer stock onto a lysogeny broth (LB) plate, or appropriate growth medium, and grow overnight at an optimal temperature based on bacterial strains of interest (typically 25 &#176;C for C. elegans natural microbes).</li>
	<li>From the LB plate, use a single colony from each bacterial isolate (e.g., 12 bacteria of the CeMbio collection) to inoculate 800 &#181;L of LB medium in separate wells of a 1 mL ...

<ol>
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Flow vermimetry has been used to characterize C. elegans genes and pathways against pathogen colonization and toxicity in several studies21,22. Here, a high throughput amenable approach is presented that uses C. elegans to investigate how intestinal microbiomes modulate their host physiology. Compared to existing methods using colony forming units (CFU) or 16S rRNA amplicon sequencing9,16</sup...

Animal evolution is under constant microbial influence1. From diverse microbes in the environment, animal hosts acquire specific partners2 that extend the capabilities of the host and drive its physiology and susceptibility to disease3. For example, metagenomic analyses of the gut microbiome uncovered enriched metabolic classes of microbial genes that may confer greater energy harvest and storage in obese mice4, many of which are also found in the human gut microbiome5. There is still a great need to establish causal relationships and pinpoint the molecular determinants of the microbiome impact, though progress has been hampered by the microbiome complexities and tractability of host systems to large-scale screening.
The model organism C. elegans provides a platform to advance molecular understanding of links between microbiome and host physiology. C. elegans possesses 20 intestinal cells with a mucosal layer and villi structures. These cells are equipped with abundant chemoreceptor genes that sense microbial products and produce antimicrobial molecules that potentially regulate their gut colonizers6,7. This conserved biology of C. elegans has led to a tremendous number of discoveries in host signaling that regulate gut microbes, including insulin signaling, TGF-beta, and MAP Kinase8,9,10.
C. elegans utilize microbes as both their diet for growth during development and microbiome as adults. With old age, some microbes may over-accumulate in the gut lumen and the host-microbe relationship shifts from symbiosis to pathogenesis11. In their natural habitats, C. elegans encounters a wide array of bacterial species12,13. Sequencing 16S rDNA from representative samples collected in natural habitats (rotten fruits, plant stem, and animal vectors) revealed that the natural microbiome of C. elegans is dominated by four bacterial phyla: Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. Within these divisions lies great variation in the diversity and richness of bacteria based on the habitat12,13,14,15. Several defined communities have been established, including the 63-member (BIGbiome)16 and 12-member (CeMbio) collections representing the top microbiome genera created for the C. elegans research community17. Both microbiomes and component strains can have a diverse impact on the physiology of C. elegans such as body size, growth rates, and stress responses9,16,17. These studies provide resources and examples to establish C. elegans as a model for microbiome research.
Here a large particle sorter (LPS) based workflow (Figure 1) is presented that utilizes the C. elegans system to simultaneously measure microbiome composition and basic measures of host physiology at the population scale. From the microbial side, the workflow is adaptable to assemble a defined microbiome or single microbes to test the robustness and plasticity of the community with increasing microbial interactions. From the host side, the workflow enables high throughput assays to measure colonization levels of fluorescent microbes in the microbiome and host physiological readout in terms of development, body size, and reproduction. Taken together, the C. elegans microbiome model enables high throughput screens to pinpoint the metabolic and genetic determinants modulating host physiology.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>15 mL conical bottom centrifuge tubes</td>
			<td>VWR</td>
			<td>10026-076</td>
			<td></td>
		</tr>
		<tr>
			<td>96 deep-well plates (1 mL)</td>
			<td>Axygen</td>
			<td>P-DW-11-C</td>
			<td></td>
		</tr>
		<tr>
			<td>96 deep-well plates (2 mL)</td>
			<td>Axygen</td>
			<td>P-DW-20-C</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well Costar plate</td>
			<td>Corning</td>
			<td>3694</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Millipore Sigma</td>
			<td></td>
			<td>Standard bacteriology agar is also sufficient.</td>
		</tr>
		<tr>
			<td>Aspirating manifold</td>
			<td>V&#38;P scientific</td>
			<td>VP1171A</td>
			<td></td>
		</tr>
		<tr>
			<td>Bleach</td>
			<td>Clorox</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bleach solution&#160;</td>
			<td></td>
			<td></td>
			<td>Mix Bleach with 5M Sodium hypochlorite 2:1 (v/v)</td>
		</tr>
		<tr>
			<td>Cell Imaging Multimode Reader</td>
			<td>Biotek</td>
			<td>Cytation 5</td>
			<td>Bacterial OD measurement</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Thermo scientific&#160;</td>
			<td>Sorvall Legend XTR</td>
			<td>For 96 well plate and conical tubes</td>
		</tr>
		<tr>
			<td>Fluorescent Microscope</td>
			<td>Nikon</td>
			<td>TiE</td>
			<td></td>
		</tr>
		<tr>
			<td>ggplot: Various R Programming Tools for Plotting Data.</td>
			<td>R package</td>
			<td>Version 3.3.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Large Particle Autosampler</td>
			<td>Union Biometrica</td>
			<td>LP Sampler</td>
			<td></td>
		</tr>
		<tr>
			<td>Large Particle Sorter</td>
			<td>Union Biometrica</td>
			<td>COPAS Biosorter</td>
			<td></td>
		</tr>
		<tr>
			<td>Levamisole</td>
			<td>Fisher</td>
			<td>AC187870100</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysogeny Broth (LB)</td>
			<td>RPI</td>
			<td>L24066</td>
			<td>Standard LB home-made recipes using Bacto-tryptone, yeast extract, and NaCl are also sufficient.</td>
		</tr>
		<tr>
			<td>M9 solution&#160;</td>
			<td></td>
			<td></td>
			<td>22 mM KH2PO4 monobasic, 42.3 mM Na2HPO4, 85.6 mM NaCl, 1 mM MgSO4</td>
		</tr>
		<tr>
			<td>Nematode Growth Medium</td>
			<td>RPI</td>
			<td>N81800-1000.0</td>
			<td>1 mM CaCl2, 25 mM KPO4 pH 6.0, 1 mM MgSO4 added after autoclaving.</td>
		</tr>
		<tr>
			<td>RStudio</td>
			<td>GNU</td>
			<td>Version 1.3.1093</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hypochlorite</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td>5M NaOH</td>
		</tr>
		<tr>
			<td>Stereo Microscope</td>
			<td>Nikon</td>
			<td>SMZ745</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 10 cm diameter petri dishes</td>
			<td>Corning</td>
			<td>351029</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 12-well plates</td>
			<td>VWR</td>
			<td>10062-894</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 24-well plates</td>
			<td>VWR</td>
			<td>10062-896</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 6 cm diameter petri dishes</td>
			<td>Corning</td>
			<td>351007</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
	</tbody>
</table>

application of flow vermimetry for quantification and analysis of the caenorhabditis elegans gut microbiome

The composition of the gut microbiome can have a dramatic impact on host physiology throughout the development and the life of the animal. Measuring compositional changes in the microbiome is crucial in identifying the functional relationships between these physiological changes. Caenorhabditis elegans has emerged as a powerful host system to examine the molecular drivers of host-microbiome interactions. With its transparent body plan and fluorescent-tagged natural microbes, the relative levels of microbes within the gut microbiome of an individual C. elegans animal can be easily quantified using a large particle sorter. Here we describe the procedures for the experimental setup of a microbiome, collection, and analysis of C. elegans populations in the desired life stage, operation, and maintenance of the sorter, and statistical analyses of the resulting datasets. We also discuss considerations for optimizing sorter settings based on the microbes of interest, the development of effective gating strategies for C. elegans life stages, and how to utilize sorter capabilities to enrich animal populations based on gut microbiome composition. Examples of potential applications will be presented as part of the protocol, including the potential for scalability to high-throughput applications.

Defining adult and larvae population gates 
Here, synchronized C. elegans L1s were grown on an NGM plate seeded with E. coli OP50 (Eco), a standard laboratory diet. C. elegans populations were collected for LPS analysis after 96 h or 120 h of growth at 20 &#176;C (Figure 2A). A dot plot of extinction (EXT, a proxy of body density) versus time-of-flight (TOF, a proxy of body length) creates two visually separated clouds of animals. Each dot rep...

Watch this Scientific Journal Video about Application of Flow Vermimetry for Quantification and Analysis of the Caenorhabditis elegans Gut Microbiome at JoVE.com

Application of Flow Vermimetry for Quantification and Analysis of the Caenorhabditis elegans Gut Microbiome

Caenorhabditis elegans is a powerful model to examine the molecular determinants driving host-microbiome interactions. We present a high throughput pipeline profiling the single animal levels of gut microbiome colonization together with key aspects of the C. elegans physiology.

Application of Flow Vermimetry for Quantification and Analysis of the Caenorhabditis elegans Gut Microbiome

The composition of the gut microbiome can have a dramatic impact on host physiology throughout the development and the life of the animal. Measuring ...

The gut microbiome plays important roles in shaping host's physiology. This protocol, in particular, allows for high throughput assessment of fluorescent gut microbe colonization levels in single, cellular animals on a large scale. One major benefit of this method is the ability to monitor the gut microbiome of live animals in real time, which allows for the identification and correlation of any changes with the host's physiology.Demonstrating the procedure will be Dana Blackburn, a research associate from my laboratory. Begin by washing the worms off the bacterial lawn with one to two milliliters of M9-TX. Transfer the worms to a sterilized two milliliter 96 well deep plate.Pellet them at 300 G for one minute and remove the liquid using an aspirating manifold. Using a 1.2 milliliter multi-channel pipette, add 1.8 milliliters of M9-TX to each well of the deep well plate mixed by pipetting a couple of times and centrifuge at 300 G for one minute. After the final wash, bring the volume in each well to 100 microliters, using the aspirating manifold.Add 100 microliters of 10 millimolar levamisole and M9-T to each well, and allow the worms to paralyze for five minutes. Then add 4%bleach solution to each well for two minutes to reduce bacterial clumps. After the bleach treatment, add M9-TX into each well of the plate to wash the worms.Centrifuge the plate and aspirate to a final volume of 100 microliters after the second wash. Transfer the worms to a flat bottom 96 well plate, containing 150 microliters of 10 millimole of levamisole and M9-TX. Keep the worm density at 50 to 100 worms per well and split the worms into multiple wells if the population is too crowded.Turn on the air compressor, computer and LPS instrument. Check and empty the waste tank. Check and refill sheath and water tanks if the volume is low.Ensure the 250 micrometers fluidic and optical core assembly is in place. Connect and turn on the autosampler. Open the autosampler instrument software to open the autosampler and the LPS software.On the LPS software window, go to file and click new experiment, then select file again and click new sample check. Enable lasers to turn on 488 and 561 nanometer lasers if it has not been done already. Now create templates for acquisition dot plots, using time of flight, extinction and fluorescent channels in the LPS software window.Right click within the body of a graph to modify the scaling. Next, load the control samples. On the autosampler window, select prime, go to file, click open script to select the correct built-in script and click okay.Go to plate template on the sampler software menu to select the desired wells for analysis. After loading and securing the plate onto the autosampler stage, press run plate on the autosampler window and save the file when prompted, then click the store current data button on the top ribbon in the LPS software window and save the data again. Open the LPS software.Navigate to file and select new experiment, then go back to file and click new sample. Create a dot plot with the time of flight on the X axis and extinction on the Y axis. Create another dot plot with the time of flight on the X axis and red on the Y axis.Ensure to check enable lasers to activate the 488 and the 561 nanometer lasers. Position the control sample tube on the sample port, then click acquire within the acquire and dispense dialogue box. When prompted, ensure to save the file.Once enough worms have been measured to differentiate populations, select abort in the dot plot showing the time of flight versus extinction. Draw a gate around the area representing the adult population. Then navigate to view, click gating hierarchy and check that the fluorescent gates are correctly listed under the adult population gate.In the time of flight versus red dot plot, create gates around the high and low red value areas to highlight the regions of interest showing microbiome colonization in adult worms. Once settings are optimized, proceed to file and click save experiment, then click file and select save sample. To load the collection apparatus, select load plate A to allow the collection stage to move into a position primed for loading either a collection tube or a 96 well plate.For dispensing to a 96 well plate, go to the setup section and select plates, then click on calibrated plates and choose 96 well plate. Next, select the wells to which the worms will be sorted and input the number of objects to be sorted into each well. Be sure to specify the gated regions of interest as well.If there are multiple gated regions being sorted into the same plate, ensure to check the box marked gate each well. Click okay to save the changes. After sorting numbers and assigning the locations, load the sample onto the sample port and click on the fill plate buttons from the acquire and dispense dialogue box to initiate dispensing into a 96 well plate.Higher extension and time of flight values are observed in adults compared to larvae. Progenies from two day old adults were dominated by L1 and L2 stages, while most progeny from three day old adults reached L3 and L4 stages. When grown on E.coli, the time of flight and extension values increased on day three compared to day two.When grown on ochrobactrum, BH three and mixed cultures, cenor abdidas allegands showed differences in time of flight and extension values. Increased ochrobactrum BH3 colonization was observed in the mixed condition than in ochrobactrum BH3 alone. In contrast, green, fluorescent values indicated lower OP50 colonization in the mixed condition than in OP50 alone.The worms are heavily skewed toward the Y axis, suggesting OP50 colonization is low in most worms, while levels of ochrobactrum, BH3 colonization are evenly distributed in the population. The relationship between ochrobactrum, BH3 colonization levels and host's development such as body density and the differences in reproduction patterns was also observed. The three-day old adults grown on the two member mix, microbiome exhibited a wide range of RFP intensity, indicating individual variations in ochrobactrum colonization within the group.RFP images of the wells containing 15 sorted and individual worms from high and low RFP gates are shown. The most important thing is to remember to use appropriate controls for all of the steps to ensure that the protocol and the machine are working properly. In real time, animals with specific features can be used to isolate strains from host or microbial mutant pools to identify genes that regulate post microbe interactions.Isolated animals can also be used for single animal or enriched phenotypic pool based downstream analyses, like RNA-seq or the like. Really, the opportunities are truly endless.

application-flow-vermimetry-for-quantification-analysis

Research

JoVE Journal

Biology

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 ...

Prostaglandin Extraction and Analysis in Caenorhabditis elegans

Caenorhabditis elegans is emerging as a powerful animal model to study the biology of lipids1-9. Prostaglandins are an important class of eicosanoids, which are lipid signals derived from polyunsaturated fatty acids (PUFAs)10-14. These signalling molecules are difficult to study because of their low abundance and reactive nature. The characteristic feature of prostaglandins is a cyclopentane ring structure located within the fatty acid backbone. In mammals, prostaglandins can be formed through cyclooxygenase enzyme-dependent and -independent pathways10,15. C. elegans synthesizes a wide array of prostaglandins independent of cyclooxygenases6,16,17. A large class of F-series prostaglandins has been identified, but the study of eicosanoids is at an early stage with ample room for new discoveries. Here we describe a procedure for extracting and analyzing prostaglandins and other eicosanoids. Charged lipids are extracted from mass worm cultures using a liquid-liquid extraction technique and analyzed by liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The inclusion of deuterated analogs of prostaglandins, such as PGF2 &alpha;-d4 as an internal standard is recommended for quantitative analysis. Multiple reaction monitoring or MRM can be used to quantify and compare specific prostaglandin types between wild-type and mutant animals. Collision-induced decomposition or MS/MS can be used to obtain information on important structural features. Liquid chromatography mass spectrometry (LC-MS) survey scans of a selected mass range, such as m/z 315-360 can be used to evaluate global changes in prostaglandin levels. We provide examples of all three analyses. These methods will provide researchers with a toolset for discovering novel eicosanoids and delineating their metabolic pathways.

Prostaglandin Extraction and Analysis in Caenorhabditis elegans

In this paper, we describe an optimized procedure for extracting and analyzing prostaglandins and other eicosanoids from C. elegans using LC-MS/MS.

Caenorhabditis elegans is emerging as a powerful animal model to study the biology of lipids1-9. Prostaglandins are an important class of eicosanoids, ...

Quantification of Lipid Abundance and Evaluation of Lipid Distribution in Caenorhabditis elegans by Nile Red and Oil Red O Staining

Caenorhabditis elegans is an exceptional model organism in which to study lipid metabolism and energy homeostasis. Many of its lipid genes are conserved in humans and are associated with metabolic syndrome or other diseases. Examination of lipid accumulation in this organism can be carried out by fixative dyes or label-free methods. Fixative stains like Nile red and oil red O are inexpensive, reliable ways to quantitatively measure lipid levels and to qualitatively observe lipid distribution across tissues, respectively. Moreover, these stains allow for high-throughput screening of various lipid metabolism genes and pathways. Additionally, their hydrophobic nature facilitates lipid solubility, reduces interaction with surrounding tissues, and prevents dissociation into the solvent. Though these methods are effective at examining general lipid content, they do not provide detailed information about the chemical composition and diversity of lipid deposits. For these purposes, label-free methods such as GC-MS and CARS microscopy are better suited, their costs notwithstanding.

Quantification of Lipid Abundance and Evaluation of Lipid Distribution in Caenorhabditis elegans by Nile Red and Oil Red O Staining

Nile red staining of fixed Caenorhabditis elegans is a method for quantitative measurement of neutral lipid deposits, while oil red O staining facilitates qualitative assessment of lipid distribution among tissues.

Caenorhabditis elegans is an exceptional model organism in which to study lipid metabolism and energy homeostasis. Many of its lipid genes are conserved ...

Purification and Analysis of Caenorhabditis elegans Extracellular Vesicles

The secretion of small membrane-bound vesicles into the external environment is a fundamental physiological process of all cells. These extracellular vesicles (EVs) function outside the cell to regulate global physiological processes by transferring proteins, nucleic acids, metabolites, and lipids between tissues. EVs reflect the physiological state of their cells of origin. EVs are implicated to have fundamental roles in virtually every aspect of human health. Thus, EV protein and genetic cargos are being increasingly analyzed for biomarkers of health and disease. However, the EV field still lacks a tractable invertebrate model system that permits the study of EV cargo composition. C. elegans is well suited for EV research because it actively secretes EVs outside of its body into its external environment, permitting facile isolation. This article provides all the necessary information for generating, purifying, and quantifying these environmentally secreted C. elegans EVs including how to work quantitatively with very large populations of age-synchronized worms, purifying EVs, and a flow cytometry protocol that directly measures the number of intact EVs in the purified sample. Thus, the large library of genetic reagents available for C. elegans research can be tapped into for investigating the impacts of genetic pathways and physiological processes on EV cargo composition.

Purification and Analysis of Caenorhabditis elegans Extracellular Vesicles

This article presents methods for generating, purifying, and quantifying Caenorhabditis elegans extracellular vesicles.

The secretion of small membrane-bound vesicles into the external environment is a fundamental physiological process of all cells. These extracellular ...

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, ...

Automating Aggregate Quantification in Caenorhabditis elegans

A rise in the prevalence of neurodegenerative protein conformational diseases (PCDs) has fostered a great interest in this subject over the years. This increased attention has called for the diversification and improvement of animal models capable of reproducing disease phenotypes observed in humans with PCDs. Though murine models have proven invaluable, they are expensive and are associated with laborious, low-throughput methods. Use of the Caenorhabditis elegans nematode model to study PCDs has been justified by its relative ease of maintenance, low cost, and rapid generation time, which allow for high-throughput applications. Additionally, high conservation between the C. elegans and human genomes makes this model an invaluable discovery tool. Nematodes that express fluorescently tagged tissue-specific polyglutamine (polyQ) tracts exhibit age- and polyQ length-dependent aggregation characterized by fluorescent foci. Such reporters are often employed as proxies to monitor changes in proteostasis across tissues. Manual aggregate quantification is time-consuming, limiting experimental throughput. Furthermore, manual foci quantification can introduce bias, as aggregate identification can be highly subjective. Herein, a protocol consisting of worm culturing, image acquisition, and data processing was standardized to support high-throughput aggregate quantification using C. elegans that express intestine-specific polyQ. By implementing a C. elegans-based image processing pipeline using CellProfiler, an image analysis software, this method has been optimized to separate and identify individual worms and enumerate their respective aggregates. Though the concept of automation is not entirely unique, the need to standardize such procedures for reproducibility, elimination of bias from manual counting, and increase throughput is high. It is anticipated that these methods can drastically simplify the screening process of large bacterial, genomic, or drug libraries using the C. elegans model.

Automating Aggregate Quantification in Caenorhabditis elegans

The following protocol describes the development and optimization of a high-throughput workflow for worm culturing, fluorescence imaging, and automated image processing to quantify polyglutamine aggregates as an assessment of changes in proteostasis.

A rise in the prevalence of neurodegenerative protein conformational diseases (PCDs) has fostered a great interest in this subject over the years. This ...

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.

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.

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

Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline

During meiosis, homologous chromosomes must recognize and adhere to one another to allow for their correct segregation. One of the key events that secures the interaction of homologous chromosomes is the assembly of the synaptonemal complex (SC) in meiotic prophase I. Even though there is little sequence homology between protein components within the SC among different species, the general structure of the SC has been highly conserved during evolution. In electron micrographs, the SC appears as a tripartite, ladder-like structure composed of lateral elements or axes, transverse filaments, and a central element. 
However, precisely identifying the localization of individual components within the complex by electron microscopy to determine the molecular structure of the SC remains challenging. By contrast, fluorescence microscopy allows for the identification of individual protein components within the complex. However, since the SC is only ~100 nm wide, its substructure cannot be resolved by diffraction-limited conventional fluorescence microscopy. Thus, determining the molecular architecture of the SC requires super-resolution light microscopy techniques such as structured illumination microscopy (SIM), stimulated-emission depletion (STED) microscopy, or single-molecule localization microscopy (SMLM). 
To maintain the structure and interactions of individual components within the SC, it is important to observe the complex in an environment that is close to its native environment in the germ cells. Therefore, we demonstrate an immunohistochemistry and imaging protocol that enables the study of the substructure of the SC in intact, extruded Caenorhabditis elegans germline tissue with SMLM and STED microscopy. Directly fixing the tissue to the coverslip reduces the movement of the samples during imaging and minimizes aberrations in the sample to achieve the high resolution necessary to visualize the substructure of the SC in its biological context.

Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline

Super-resolution microscopy can provide a detailed insight into the organization of components within the synaptonemal complex in meiosis. Here, we demonstrate a protocol to resolve individual proteins of the Caenorhabditis elegans synaptonemal complex.

During meiosis, homologous chromosomes must recognize and adhere to one another to allow for their correct segregation. One of the key events that secures ...

Compost Microcosms as Microbially Diverse, Natural-like Environments for Microbiome Research in Caenorhabditis elegans

The nematode Caenorhabditis elegans is emerging as a useful model for studying the molecular mechanisms underlying interactions between hosts and their gut microbiomes. While experiments with well-characterized bacteria or defined bacterial communities can facilitate the analysis of molecular mechanisms, studying nematodes in their natural microbial context is essential for exploring the diversity of such mechanisms. At the same time, the isolation of worms from the wild is not always feasible, and, even when possible, sampling from the wild restricts the use of the genetic toolkit otherwise available for C. elegans research. The following protocol describes a method for microbiome studies utilizing compost microcosms for the in-lab&#160;growth in microbially diverse and natural-like environments.
Locally sourced soil can be enriched with produce to diversify the microbial communities in which worms are raised and from which they are harvested, washed, and surface-sterilized for subsequent analyses. Representative experiments demonstrate the ability to modulate the microbial community in a common soil by enriching it with different produce and further demonstrate that worms raised in these distinct environments assemble similar gut microbiomes distinct from their respective environments, supporting the notion of a species-specific core gut microbiome. Overall, compost microcosms provide natural-like in-lab environments for microbiome research as an alternative to synthetic microbial communities or to the isolation of wild nematodes.

Compost Microcosms as Microbially Diverse, Natural-like Environments for Microbiome Research in Caenorhabditis elegans

Compost microcosms bring the microbial diversity found in nature into the laboratory to facilitate microbiome research in Caenorhabditis elegans. Provided here are protocols for setting up microcosm experiments, with the experiments demonstrating the ability to modulate environmental microbial diversity to explore the relationships between environmental microbial diversity and worm gut microbiome composition.

The nematode Caenorhabditis elegans is emerging as a useful model for studying the molecular mechanisms underlying interactions between hosts and their ...

Lipid Supplementation for Longevity and Gene Transcriptional Analysis in Caenorhabditis elegans

Aging is a complex process characterized by progressive physiological changes resulting from both environmental and genetic contributions. Lipids are crucial in constituting structural components of cell membranes, storing energy, and as signaling molecules. Regulation of lipid metabolism and signaling is essential to activate distinct longevity pathways. The roundworm Caenorhabditis elegans is an excellent and powerful organism to dissect the contribution of lipid metabolism and signaling in longevity regulation. Multiple research studies have described how diet supplementation of specific lipid molecules can extend C. elegans lifespan; however, minor differences in the supplementation conditions can cause reproducibility issues among scientists in different labs. Here, two detailed supplementation methods for C. elegans are reported employing lipid supplementation either with bacteria seeded on plates or bacterial suspension in liquid culture. Also provided herein are the details to perform lifespan assays with lifelong lipid supplementation and qRT-PCR analysis using a whole worm lysate or dissected tissues derived from a few worms. Using a combination of longitudinal studies and transcriptional investigations upon lipid supplementation, the feeding assays provide dependable approaches to dissect how lipids influence longevity and healthy aging. This methodology can also be adapted for various nutritional screening approaches to assess changes in a subset of transcripts using either a small number of dissected tissues or a few animals.

Lipid Supplementation for Longevity and Gene Transcriptional Analysis in Caenorhabditis elegans

The present protocol describes lipid supplementation methods in liquid and on-plate cultures for Caenorhabditis elegans, coupled with longitudinal studies and gene transcriptional analysis from bulk or a few worms and worm tissues.

Aging is a complex process characterized by progressive physiological changes resulting from both environmental and genetic contributions. Lipids are ...