This study was supported by the Korea Institute of Science and Technology intramural research grant (2E27513) and the High Value-added Food Technology Development Program (IPET) funded by the Ministry of Agriculture, Food and Rural Affairs (315067-03).

NOTE: The entire experiment must be performed in a clean isolated laboratory maintained at 20 &#176;C with low dust and with minimization of contamination during worm and bacterial handling. For this purpose, experiments must be performed under the flame of an alcohol lamp or using a clean bench.
1. Maintenance of C. elegans and Egg Preparation for the Chemical Test
<ol>
	<li>Maintain C. elegans N2 (var. Bristol) on an NGM agar plate fed with live E. coli OP50 at 20 &#176;C12,13.</li>
	<li>Prepare age-synchronized eggs using either bleach solution treatment5 or the time egg laying method6,14,15. 
	NOTE: Before egg preparation, coat the etoposide-containing NGM plate with heat-inactivated E. coli OP50 as described below. Heat-inactivated E coli OP50 is used to minimize the metabolic activity of E. coli6,16.</li>
</ol>
2. Preparation of Heat-inactivated E. coli OP50 to Feed C. elegans During the Toxicity Test
<ol>
	<li>Prepare 500 mL of double yeast tryptone (DYT) medium as described in Table 1, and inoculate a single colony of E. coli OP50 cultured on a Luria-Bertani (LB) agar plate5.</li>
	<li>Incubate the E. coli OP50 in a shaking incubator for 14 h at 37 &#176;C and 150 rpm.</li>
	<li>After centrifugation for 30 min at 3,220 x g and 20 &#176;C, remove all supernatant DYT medium, and add a pre-mixture of 25 mL of S-buffer, 250 &#181;L of 1 M MgSO4, and 25 &#181;L of 5 mg/mL cholesterol (dissolved in ethanol). All these solutions are sterile.</li>
	<li>Resuspend the bacteria and transfer them to a 50-mL disposable plastic tube.</li>
	<li>For the heat-inactivation, incubate the resuspended E. coli OP50 in a water bath for 30 min at 65 &#176;C.</li>
	<li>Cool down to room temperature and store at 4 &#176;C until use. This can be stored for up to one month.</li>
</ol>
3. Preparation of NGM Plates Containing Either 1% DMSO or 750 &#181;M Etoposide
<ol>
	<li>Prepare two clean 200 mL glass bottles. Add 0.6 g of NaCl, 0.5 g of peptone, 3.4 g of agar, and 195 mL of distilled water, and a magnetic stirrer to one bottle. Add a magnetic stirrer to the other empty bottle.</li>
	<li>Autoclave these two bottles for 15 min at 121 &#176;C, and then cool down the bottles in a water bath for 30 min at 55 &#176;C.</li>
	<li>Add 0.2 mL of 1 M CaCl2, 0.2 mL of 5 mg/mL cholesterol, 0.2 mL of 1 M MgSO4, and 5 mL of 1 M KPO4 (all these solutions are sterile) and then mix them by magnetic stirring on a hot plate at 55 &#176;C.</li>
	<li>Divide the mixed NGM medium into two bottles with the same volume (100 mL each). Next, add 1 mL of DMSO to one bottle, mix it again using the magnetic stirring. Store the other bottle in a water bath at 55 &#176;C until the next step. Aliquot 3 mL of the DMSO-containing medium to each 35 x 10 mm2 Petri dish. Approximately 33 DMSO-containing NGM plates can be made from this step.</li>
	<li>Mix the other bottle using the magnetic stirring, add 1 mL of 75 mM etoposide (stock dissolved in DMSO), mix again, and repeat the aliquot procedure (step 3.4). Approximately 33 etoposide (750 &#181;M)-containing NGM plates can be made from this step. 
	NOTE: In the correlated previous paper6, we tested 0, 250, 500, and 1,000 &#181;M of etoposide. Based on that data, we chose the 750 &#181;M of etoposide dose in this paper.</li>
	<li>Cool down the chemical-containing NGM plates to room temperature by leaving them at room temperature for approximately 3 h, and store them at 4 &#176;C until use. 
	NOTE: In the case of light-sensitive chemicals, block out light to minimize the light-induced decomposition. 
	NOTE: Optionally, make a normal NGM plate without chemicals for the egg laying assay, which can be performed using two different chemical treatment conditions as described below.</li>
	<li>Add 100 &#181;L of heat-inactivated E. coli OP50 (as described in section 2) and spread on each NGM plate. Allow to dry overnight in a C. elegans incubator at 20 &#176;C for the chemical test.</li>
</ol>
4. Measurement of C. elegans Growth
<ol>
	<li>Transfer the age-synchronized C. elegans eggs to the NGM plate supplemented with 1% DMSO or 750 &#181;M etoposide.</li>
	<li>Incubate C. elegans in an incubator at 20 &#176;C for 4 days. Observe the worms using a stereo microscope, and take microscopic images every day. Usually 20X magnification (1X objective lens, 2X zoom magnification, and 10X eyepiece lens) is appropriate for the growth observation of C. elegans. Also take a microscopic image of the microscope stage micrometer for the worm size calibration. 
	NOTE: Starvation affects the toxicity test. Therefore, feed with sufficient bacteria or adjust the&#160;transferred C. elegans egg numbers at the beginning. Observe until 3 days to exclude the possibility of starvation.</li>
	<li>Measure the body length of C. elegans treated with DMSO or etoposide at each time point using ImageJ software. 
	NOTE: For each sample measurement, 50 worms are sufficient for the statistical analysis.
	<ol>
		<li>In ImageJ, open the microscope stage micrometer image (&#39;File&#39; &#8594; &#39;Open&#39;). 
		NOTE: The micrometer image and worm images (step 4.2) must be the same magnification.</li>
		<li>Drag a line of 1,000 &#181;m on the micrometer calibration image by using &#39;Straight Line&#39; tool.</li>
		<li>Click &#39;Analyze&#39; &#8594; &#39;Set Scale&#39; and input 1,000 and &#181;m into the &#39;Known distance&#39; box and &#39;Unit of length&#39; box, respectively. Check &#39;Global&#39; and click &#39;OK&#39;.</li>
		<li>Open the worm images (&#39;File&#39; &#8594; &#39;Open&#39;). Draw a line along the feature of each worm by using &#39;Freehand Line&#39; tool. Obtain the body length data by clicking &#39;Analyze&#39; &#8594; &#39;Measure&#39;.</li>
		<li>Repeat these steps for 50 worms.</li>
	</ol>
	</li>
</ol>
5. C. elegans Egg Laying Assay
<ol>
	<li>Incubate the age-synchronized eggs on the NGM plate containing DMSO or etoposide for 64 h (before first birth) until the young adult stage at 20 &#176;C. 
	NOTE: It is optional to use the worms from the growth measurement experiments. It is convenient to do the growth measurement and egg laying assay together.</li>
	<li>Transfer 5 adult worms to the new NGM plates without chemicals (condition 1, chemical treatment within a certain period of time, from eggs to young adult stage) or new NGM plate containing the same chemical pretreatment (condition 2, continuous exposure of chemicals through the overall experimental period), and then incubate them for 24 h. 
	NOTE: It is recommended to make replicates using 3-5 NGM plates for each treatment; these replicates can be used for statistical analysis.</li>
	<li>Transfer to the new NGM plate as described above, and count the number of eggs every day. Count the worms that crawled off, died, and were internally hatched.</li>
	<li>Repeat these steps until the worms lay no more eggs, usually in 5 days.</li>
	<li>Calculate the number of eggs laid per worm from each plate, and sum these values every day for 5 days to determine the total number of eggs laid. 
	NOTE: Exclude the number of worms that crawled off and internally hatched from the calculation.</li>
</ol>

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The authors have nothing to disclose.

In this article, we describe the toxicity evaluation of chemicals in C. elegans, a soil nematode, using etoposide as a toxicant example. For this purpose, we used two experimental conditions. In the first set, C. elegans were grown on etoposide containing plates from eggs to the young adult stage, and then the worms were allowed to lay eggs on normal NGM plates without chemicals. In the second experimental set, C. elegans were continuously treated with etoposide throughout the whole experimenta...

Toxicological evaluation is essential for the development of pharmaceuticals, nutraceuticals, and cosmeceuticals, as well as the risk assessment of various environmental toxins. The rodent model is one of the most popular in vivo experimental systems for this toxicology study; alternatively, non-mammalian organisms such as C. elegans are also widely used. Non-mammalian toxicological evaluation models are beneficial because of not only animal ethical issues but also their convenience and usefulness considering cost-effectiveness, maintainability, speed, and reproducibility1,2,3,4.
C. elegans, a soil round worm, has been exploited as a model animal in various basic and applied biology and chemistry research. It is a 1 mm long, transparent nematode, which is simply maintained in solid or liquid Nematode Growth Media (NGM) fed with the bacterial strain Escherichia coli OP50. C. elegans has a short life cycle, and wild-type N2 C. elegans lays approximately 300 eggs. Therefore, it is easily propagated to be used as experimental materials3,4,5. C. elegans has also been widely used in the toxicological studies of many drugs and environmental pollutants6,7,8,9.
Because many anticancer drugs target rapidly dividing cancer cells, they can also damage rapidly dividing normal cells such as bone marrow, intestinal epithelium, and hair follicle cells. For example, topoisomerase inhibitory anticancer drugs target the DNA replication process of cancer cells; therefore, they also inhibit rapidly dividing normal cells. Every living organism has topoisomerases, and these topoisomerase inhibitors most likely impact environmental ecosystems6,10,11. Thus, a drug toxicological evaluation platform using a model animal is valuable for both the development of pharmaceuticals and environmental risk assessment.
In this article, we describe the detailed protocols to test the toxicity of etoposide, which is a clinical anticancer agent that targets topoisomerase II, as a model toxic chemical in C. elegans. For this purpose, we will describe the measurement method of body size and the total number of eggs laid in C. elegans treated with etoposide.

<table><tbody><tr><td>Agar</td><td>Affymetrix, USA</td><td>10906</td><td></td></tr><tr><td>&lt;em&gt;Caenorhabditis elegans&lt;/em&gt; N2</td><td>Caenorhabditis Genetics Center (CGC)</td><td></td><td>Wild type</td></tr><tr><td>Cholesterol</td><td>Sigma, USA</td><td>C3045</td><td></td></tr><tr><td>Dimethyl sulfoxide</td><td>Sigma, USA</td><td>D2650</td><td></td></tr><tr><td>&lt;em&gt;Escherichia coli &lt;/em&gt;OP50</td><td>Caenorhabditis Genetics Center (CGC)</td><td></td><td></td></tr><tr><td>Etoposide</td><td>Sigma, USA</td><td>E1383</td><td></td></tr><tr><td>Image J software (ver 1.4)</td><td>Natinoal Institute of Health, USA</td><td></td><td>https://imagej.nih.gov/ij/</td></tr><tr><td>Microscope camera</td><td>Jenopitk, Progress Gryphax, Germany</td><td></td><td></td></tr><tr><td>Peptone</td><td>Merck, USA</td><td>107213</td><td></td></tr><tr><td>35 &amp;times; 10 mm Petri dish</td><td>SPL Life Sciences, South Korea</td><td>10035</td><td></td></tr><tr><td>90 &amp;times; 15 mm Petri dish</td><td>SPL Life Sciences, South Korea</td><td>10090</td><td></td></tr><tr><td>Stereo microscope</td><td>Nikon, Japan</td><td>SMZ800N</td><td></td></tr><tr><td>Yeast extract</td><td>Becton Dickinson, USA</td><td>212750</td><td></td></tr></tbody></table>

measuring the effect of chemicals on the growth and reproduction of caenorhabditis elegans

Toxicological evaluation is crucial for understanding the effects of chemicals on living organisms in basic and applied biological science fields. A non-mammalian soil round worm, Caenorhabditis elegans, is a valuable model organism for toxicology studies due to its convenience and lack of animal ethics issues compared with mammalian animal systems. In this protocol, a detailed procedure of toxicological evaluation of chemicals in C. elegans is described. A clinical anticancer drug, etoposide, which targets human topoisomerase II and inhibits DNA replication of human cancer cells, was selected as a model testing chemical. Age-synchronized C. elegans eggs were exposed to either dimethyl sulfoxide (DMSO) or etoposide, and then the growth of C. elegans was monitored every day for 4 days by the stereo microscope observation. The total number of eggs laid from C. elegans treated with DMSO or etoposide was also counted by using the stereo microscope. Etoposide treatment significantly affected the growth and reproduction of C. elegans. By comparison of the total number of eggs laid from worms with different treatment periods of chemicals, it can be decided that the reproductive toxicity of chemicals on C. elegans reproduction is reversible or irreversible. These protocols may be helpful for both the development of various drugs and risk assessment of environmental toxicants.

The treatment of etoposide (24-96 h) significantly retarded the growth of C. elegans. After 96 h of incubation, etoposide-treated worms grew to 0.86 mm in body length, while the vehicle-treated worms grew to 1.04 mm (Figure 1). Growth retardation was also apparently observed under stereo microscope observation (Figure 2). We started to see eggs from the vehicle-treated worms at 72 h of incubation. On the other hand, eggs...

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Measuring the Effect of Chemicals on the Growth and Reproduction of Caenorhabditis elegans

A basic protocol to evaluate the toxicity of chemicals in a model animal, Caenorhabditis elegans, is described. The method is convenient and useful for the development of pharmaceuticals as well as for the risk assessment of various environmental pollutants.

Measuring the Effect of Chemicals on the Growth and Reproduction of Caenorhabditis elegans

Toxicological evaluation is crucial for understanding the effects of chemicals on living organisms in basic and applied biological science fields. A ...

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Medicine

16.9K Views.  Korea Institute of Science and Technology. Een basisprotocol te beoordelen van de giftigheid van chemische stoffen in een model dier, Caenorhabditis elegans, wordt beschreven. De methode is geschikt en nuttig is voor de ontwikkeling van geneesmiddelen, alsook wat betreft de risico-evaluatie van verschillende milieuverontreinigende stoffen.

Video: Measuring the Effect of Chemicals on the Growth and Reproduction of Caenorhabditis elegans

Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode Caenorhabditis elegans

Identifying the reproductive toxicity of the thousands of chemicals present in our environment has been one of the most tantalizing challenges in the field of environmental health. This is due in part to the paucity of model systems that can (1) accurately recapitulate keys features of reproductive processes and (2) do so in a medium- to high-throughput fashion, without the need for a high number of vertebrate animals.
We describe here an assay in the nematode C. elegans that allows the rapid identification of germline toxicants by monitoring the induction of aneuploid embryos. By making use of a GFP reporter line, errors in chromosome segregation resulting from germline disruption are easily visualized and quantified by automated fluorescence microscopy. Thus the screening of a particular set of compounds for its toxicity can be performed in a 96- to 384-well plate format in a matter of days. Secondary analysis of positive hits can be performed to determine whether the chromosome abnormalities originated from meiotic disruption or from early embryonic chromosome segregation errors. Altogether, this assay represents a fast first-pass strategy for the rapid assessment of germline dysfunction following chemical exposure.

Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode Caenorhabditis elegans

We describe the detailed steps of a high-throughput chemical assay in the nematode Caenorhabditis elegans used to assess germline toxicity. In this assay, disruption of germline function following chemical exposure is monitored using a fluorescent reporter specific to aneuploid embryos.

Identifying the reproductive toxicity of the thousands of chemicals present in our environment has been one of the most tantalizing challenges in the ...

Developmental Biology

A Simple Method for High Throughput Chemical Screening in Caenorhabditis Elegans

Caenorhabditis elegans is a useful organism for testing chemical effects on physiology. Whole organism small molecule screens offer significant advantages for identifying biologically active chemical structures that can modify complex phenotypes such as lifespan. Described here is a simple protocol for producing hundreds of 96-well culture plates with fairly consistent numbers of C. elegans in each well. Next, we specified how to use these cultures to screen thousands of chemicals for effects on the lifespan of the nematode C. elegans. This protocol makes use of temperature sensitive sterile strains, agar plate conditions, and simple animal handling to facilitate the rapid and high throughput production of synchronized animal cultures for screening.

A Simple Method for High Throughput Chemical Screening in Caenorhabditis Elegans

Here we describe a simple protocol for rapidly producing hundreds of nematode growth media agar, 96-well culture plates with consistent numbers of Caenorhhabditis elegans per well. These cultures are useful for the phenotypic screening of whole organisms. We focus here on using these cultures to screen chemicals for pro-longevity effects.

Caenorhabditis elegans is a useful organism for testing chemical effects on physiology. Whole organism small molecule screens offer significant advantages ...

Biochemistry

A High-throughput Assay for the Prediction of Chemical Toxicity by Automated Phenotypic Profiling of Caenorhabditis elegans

Applying toxicity testing of chemicals in higher order organisms, such as mice or rats, is time-consuming and expensive, due to their long lifespan and maintenance issues. On the contrary, the nematode Caenorhabditis elegans (C. elegans) has advantages to make it an ideal choice for toxicity testing: a short lifespan, easy cultivation, and efficient reproduction. Here, we describe a protocol for the automatic phenotypic profiling of C. elegans in a 384-well plate. The nematode worms are cultured in a 384-well plate with liquid medium and chemical treatment, and videos are taken of each well to quantify the chemical influence on 33 worm features. Experimental results demonstrate that the quantified phenotype features can classify and predict the acute toxicity for different chemical compounds and establish a priority list for further traditional chemical toxicity assessment tests in a rodent model.

A High-throughput Assay for the Prediction of Chemical Toxicity by Automated Phenotypic Profiling of Caenorhabditis elegans

A quantitative method has been developed to identify and predict the acute toxicity of chemicals by automatically analyzing the phenotypic profiling of Caenorhabditis elegans. This protocol describes how to treat worms with chemicals in a 384-well plate, capture videos, and quantify toxicological related phenotypes.

Applying toxicity testing of chemicals in higher order organisms, such as mice or rats, is time-consuming and expensive, due to their long lifespan and ...

Environment

Using Caenorhabditis elegans for Studying Trans- and Multi-Generational Effects of Toxicants

Information about toxicities of chemicals are essential in their application and waste management. For chemicals at low concentrations, the long-term effects are very important in judging their consequences in the environment and on human health. In demonstrating long-term influences, effects of chemicals over generations in recent studies provide new insight. Here, we describe protocols for studying effects of chemicals over multiple generations using free-living nematode Caenorhabditis elegans. Two aspects are presented: (1) trans-generational (TG) and (2) multi-generational effect studies, the latter of which is separated to multi-generational exposure (MGE) and multi-generational residual (MGR) effect studies. The TG effect study is robust with a simple purpose to determine whether chemical exposure to parents can result in any residual consequences on offspring. After the effects are measured on parents, sodium hypochlorite solutions are used to kill the parents and keep the offspring so as to facilitate effect measurement on the offspring. The TG effect study is used to determine whether the offspring are affected when their parent is exposed to the pollutants. The MGE and MGR effect study is systematical used to determine whether continuous generational exposure can result in adaptive responses in offspring over generations. Careful pick-up and transfer are used to distinguish generations to facilitate effect measurement on each generation. We also combined protocols to measure locomotion behavior, reproduction, lifespan, biochemical and gene expression changes. Some example experiments are also presented to illustrate the trans- and multi-generational effect studies.

Using Caenorhabditis elegans for Studying Trans- and Multi-Generational Effects of Toxicants

Trans- and multi-generational effects of persistent chemicals are essential in judging their long-term consequences in the environment and on the human health. We provide novel detailed methods for studying trans- and multi-generational effects using free-living nematode Caenorhabditis elegans.

Information about toxicities of chemicals are essential in their application and waste management. For chemicals at low concentrations, the long-term ...

High-Throughput Assay to Measure Caenorhabditis elegans Food Intake and Lifespan

Quantifying Food Intake in Caenorhabditis elegans by Measuring Bacterial Clearance

Feeding is an essential biological process for an organism&#39;s growth, reproduction, and survival. This assay aims to measure the food intake of Caenorhabditis elegans&#160;(C. elegans), an important parameter when studying the genetics of aging or metabolism. In most species, feeding is determined by measuring the difference between the amount of food provided and the amount left after a given time interval. The method presented here uses the same strategy to determine the feeding of C. elegans. It measures the amount of bacteria, the food source of C. elegans, cleared within 72 h. This method uses 96-well microtiter plates and has allowed the screening of hundreds of drugs for their ability to modulate food intake at a speed and depth not possible in other animal models. The strength of this assay is that it allows to measure feeding and lifespan simultaneously and directly measures the disappearance of food and, thus, is based on the same principles used for other organisms, facilitating species-to-species comparison.

Author Spotlight: Exploring the Relationship Between Lipotoxicity and HFpEF 

This protocol describes an assay to quantify Caenorhabditis elegans feeding rate based on measuring the clearance of bacteria in liquid culture.

Feeding is an essential biological process for an organism&#39;s growth, reproduction, and survival. This assay aims to measure the food intake of ...

Behavior

An Assay for Measuring the Effects of Ethanol on the Locomotion Speed of Caenorhabditis elegans

Alcohol use disorders are a significant public health concern, for which there are few effective treatment strategies. One difficulty that has delayed the development of more effective treatments is the relative lack of understanding of the molecular underpinnings of the effects of ethanol on behavior. The nematode, Caenorhabditis elegans (C.&#160;elegans), provides a useful model in which to generate and test hypotheses about the molecular effects of ethanol. Here, we describe an assay that has been developed and used to examine the roles of particular genes and environmental factors in behavioral responses to ethanol, in which locomotion is the behavioral output. Ethanol dose-dependently causes an acute depression of crawling on an agar surface. The effects are dynamic; animals exposed to a high concentration demonstrate an initial strong depression of crawling, referred to here as initial sensitivity, and then partially recover locomotion speed despite the continued presence of the drug. This ethanol-induced behavioral plasticity is referred to here as the development of acute functional tolerance. This assay has been used to demonstrate that these two phenotypes are distinct and genetically separable. The straightforward locomotion assay described here is suitable for examining the effects of both genetic and environmental manipulations on these acute behavioral responses to ethanol in C.&#160;elegans.

An Assay for Measuring the Effects of Ethanol on the Locomotion Speed of Caenorhabditis elegans

C. elegans is a useful model for studying the effects of ethanol on behavior. We present a behavioral assay that quantifies the effects of ethanol on the locomotion speed of crawling worms; both initial sensitivity and the development of acute functional tolerance to ethanol can be measured with this assay.

Alcohol use disorders are a significant public health concern, for which there are few effective treatment strategies. One difficulty that has delayed the ...

Neuroscience

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 ...

Biology

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

C. elegans egg-laying behavior is affected by environmental cues such as osmolarity1 and vibration2. In the total absence of food C. elegans also cease egg-laying and retain fertilized eggs in their uterus3. However, the effect of different sources of food, especially pathogenic bacteria and particularly Enterococcus faecalis, on egg-laying
	behavior is not well characterized. The egg-in-worm (EIW) assay is a useful tool to quantify the effects of different types of bacteria, in this case E. faecalis, on egg- laying behavior.
	
	EIW assays involve counting the number of eggs retained in the uterus of C. elegans4. The EIW assay involves bleaching staged, gravid adult C. elegans to remove the cuticle and separate the retained eggs from the animal. Prior to bleaching, worms are exposed to bacteria (or any type of environmental cue) for a fixed period of time. After bleaching, one is very easily able to count the number of eggs retained inside the uterus of the worms. In this assay, a quantifiable increase in egg retention after E. faecalis exposure can be easily measured. The EIW assay is a behavioral assay that may be used to screen for potentially pathogenic bacteria or the presence of environmental toxins. In addition, the EIW assay may be a tool to screen for drugs that affect neurotransmitter signaling since egg-laying behavior is modulated by neurotransmitters such as serotonin and acetylcholine5-9.

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

An egg-in-worm (EIW) assay is a useful method to quantify egg-laying behavior. Alterations in egg laying can be a behavioral response of the model organism Caenorhabditis elegans to potentially harmful environmental substances such as those produced by pathogenic bacteria.

C. elegans egg-laying behavior is  affected by environmental cues such as osmolarity1 and  vibration2. In the total absence of food C. elegans also cease ...

Measuring the Effects of Bacteria and Chemicals on the Intestinal Permeability of Caenorhabditis elegans

In living organisms, intestinal hyperpermeability is a serious symptom that leads to many inflammatory bowel diseases (IBDs). Caenorhabditis elegans is a nonmammalian animal model that is widely used as an assay system due to its short lifespan, transparency, cost-effectiveness, and lack of animal ethics issues. In this study, a method was developed to investigate the effects of different bacteria and 3,3'-diindolylmethane (DIM) on the intestinal permeability of C. elegans with a high-throughput image analysis system. The worms were infected with different gut bacteria or cotreated with DIM for 48 h and fed with fluorescein isothiocyanate (FITC)-dextran overnight. Then, the intestinal permeability was examined by comparing the fluorescence images and the fluorescence intensity inside the worm bodies. This method may also have the potential to identify probiotic and pathogenic intestinal bacteria that affect intestinal permeability in the animal model and is effective for examining the effects of harmful or health-promoting chemicals on intestinal permeability and intestinal health. However, this protocol also has some considerable limitations at the genetic level, especially for determining which genes are altered to control illness, because this method is mostly used for phenotypic determination. In addition, this method is limited to determining exactly which pathogenic substrates cause inflammation or increase the permeability of the worms' intestines during infection. Therefore, further in-depth studies, including investigation of the molecular genetic mechanism using mutant bacteria and nematodes as well as chemical component analysis of bacteria, are required to fully evaluate the function of bacteria and chemicals in determining intestinal permeability.

Measuring the Effects of Bacteria and Chemicals on the Intestinal Permeability of Caenorhabditis elegans

This protocol describes how to measure intestinal permeability of Caenorhabditis elegans. This method is helpful for basic biological research on intestinal health related to the interaction between intestinal bacteria and their host and for screening to identify probiotic and chemical agents to cure leaky gut syndrome and inflammatory bowel diseases.

In living organisms, intestinal hyperpermeability is a serious symptom that leads to many inflammatory bowel diseases (IBDs). Caenorhabditis elegans is a ...

Examining the Effect of Pesticides on Caenorhabditis elegans Neurons

Caenorhabditis elegans is a powerful model organism used in many research laboratories to understand the consequences of exposure to chemical pollutants, pesticides, and a wide variety of toxic substances. These nematodes are easy to work with and can be used to generate novel research findings, even in the undergraduate biology laboratory. A multi-week laboratory series of authentic, student-driven research projects trains students in a toolkit of techniques and approaches in behavioral measurements, cell biology, and microscopy that they then apply to their projects. One technique in that toolkit is quantifying the percentage of neurons exhibiting neurodegenerative damage following exposure to a chemical toxicant like a pesticide. Young adult C. elegans nematodes can be exposed to different concentrations of commercially available pesticides or other types of toxicants for 2-24 h. Then, undergraduate students can visualize different neuron subtypes using fluorescent-expressing strains of C. elegans. These techniques do not require sophisticated image processing software and are effective at even low magnifications, making the need for expensive confocal microscopy unnecessary. This paper demonstrates how to treat the nematodes with pesticides and how to image and score the neurons. It also provides a straightforward protocol for the microscopy and analysis of neuron morphology. The materials used for this technique are inexpensive and readily available in most undergraduate biology departments. This technique can be combined with behavioral measures like locomotion, basal slowing, or egg-laying to conduct a potentially publishable series of experiments and give undergraduate students an authentic research experience at a very low cost.

Examining the Effect of Pesticides on Caenorhabditis elegans Neurons

Young adult Caenorhabditis elegans nematodes are exposed to different concentrations of commercial pesticides or other toxicants for 2-24 h. Then, different neurons can be visualized using fluorescent-expressing strains. This paper demonstrates how to expose nematodes to pesticides and assess neuron damage.

Caenorhabditis elegans is a powerful model organism used in many research laboratories to understand the consequences of exposure to chemical pollutants, ...

Measuring the Effect of Chemicals on the Growth and Reproduction of Caenorhabditis elegans

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