Name: a plate competition assay as a quick preliminary assessment of disease suppression
Uploaded: 2018-10-28T15:00:00
Description: Watch this Scientific Journal Video about A Plate Competition Assay As a Quick Preliminary Assessment of Disease Suppression at JoVE.com

The Vermont Agricultural Experiment Station Competitive Hatch Program VT-HO1609 funded the research. Lynn Fang used the method as part of her M.S. thesis at University of Vermont6.

1. Prepare in Advance
<ol>
	<li>Master fungal culture (test organism)
	<ol>
		<li>Order from the American Type Culture Collection, Microbiology Collection9, by its teleomorph Thanatephorus cucumeris (Frank) (ATCC 10154) or MYA 4031.</li>
		<li>Alternatively: Collect local isolates as done by the authors. Seedlings of red radish (Raphanus sativus) work well as a bait plant; collect soil from a location known to have a history of damping-off or root rot caused by R. solani</e...

<ol>
	<li>Gonzalez Garcia, G., Onco, M. A. P., Susan, V. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review.+Biology+and+systematics+of+the+form+genus+Rhizoctonia.">Review. Biology and systematics of the form genus Rhizoctonia.</a> Spanish Journal of Agricultural Research. 4 (1), 55-79 (2006).</li><li>Bonanomi, G., Antignani, V., Pane, C., Scala, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suppression+of+soilborne+fungal+diseases+with+organic+amendments.">Suppression of soilborne fungal diseases with organic amendments.</a> Journal of Plant Pathology. 89, 311-324 (2007).</li><li>Noble, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risks+and+benefits+of+soil+amendment+with+composts+in+relation+to+plant+pathogens.">Risks and benefits of soil amendment with composts in relation to plant pathogens.</a> Australasian Plant Pathology. 40, 157-167 (2011).</li><li>Wichuk, K. M., McCartney, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compost+stability+and+maturity+evaluation+-+a+literature+review.">Compost stability and maturity evaluation - a literature review.</a> Canadian Journal of Civil Engineering. 37, 1505-1523 (2010).</li><li>Alfano, G., Lustrato, G., Lima, G., Vitullo, D., Ranalli, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+composted+olive+mill+wastes+to+predict+potential+plant+disease+suppressiveness.">Characterization of composted olive mill wastes to predict potential plant disease suppressiveness.</a> Biological Control. 3, 199-207 (2011).</li><li>Fang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Biological indicators of compost-mediated disease suppression against the soilborne plant pathogen Rhizoctonia solani. , (2015).</li><li>Bonanomi, G., Antignani, V., Capodilupo, M., Scala, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identifying+the+characteristics+of+organic+soil+amendments+that+suppress+soilborne+plant+diseases.">Identifying the characteristics of organic soil amendments that suppress soilborne plant diseases.</a> Soil Biology and Biochemistry. 42, 136-144 (2010).</li><li>Neher, D. A., Fang, L., Weicht, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ecoenzymes+as+indicators+of+compost+to+suppress+Rhizoctonia+solani.">Ecoenzymes as indicators of compost to suppress Rhizoctonia solani.</a> Compost Science and Utilization. 25 (4), 251-261 (2017).</li><li>. ATCC&#174; Mycology Culture Guide Available from: <a target="_blank" href="https://www.atcc.org/~/media/PDFs/Culture%20Guides/Mycology_Guide.ashx">https://www.atcc.org/~/media/PDFs/Culture%20Guides/Mycology_Guide.ashx</a> (2018)</li><li>Berns, A. E., Phillip, H., Narres, H. -. D., Burauel, P., Vereecken, H., Tappe, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+gamma-sterilization+and+autoclaving+on+soil+organic+matter+structure+as+studied+by+solid+state+NMR,+UV+and+fluorescence+spectroscopy.">Effect of gamma-sterilization and autoclaving on soil organic matter structure as studied by solid state NMR, UV and fluorescence spectroscopy.</a> European Journal of Soil Science. 59, (2008).</li></ol>

We know from previous research, that certain composts are effective at suppressing R. solani and that the suppressive effects are due to the microbes living in the compost, not the abiotic properties of compost6,8. The use of autoclaving as a means to &#39;kill&#39; microbiota has been criticized because it affects the carbon chemistry of the media10. We compared the use of autoclaving to vacuum filtration through Whatman No. 1 pa...

Rhizoctonia represents a broad complex of fungi, of which Thanatephorus cucumeris (Frank) Donk (anamorph = Rhizoctonia solani K&#252;hn) is the pathogen causing root rot and damping-off1. Rhizoctonia solani is an aggressive pathogen and a saprophyte that can survive as sclerotia under adverse environmental conditions1. As a result, it has a global distribution and can cause disease on wide range of plant hosts including Solanaceae, Fabaceae, Asteraceae, and Brassicaceae resulting in serious economic losses.
Compost has the capacity to harbor biocontrol agents for certain plant pathogens2. However, not all composts are alike nor do they affect all pathogens similarly3. Wood-based carbon has higher lignin to cellulose ratios than hay or straw-carbon based composts. R. solani prefers readily available carbon found in straw. In contrast, biological control fungi, such as Trichoderma spp., are more effective when carbon is less readily available. Beneficial fungi and bacteria into compost can suppress plant disease through competition, antagonism or regulating plant growth3. The proposed assay primarily detects antagonism created by production of antibiotics, ecoenzymes or chelators that are detrimental to the pathogen.
Plant bioassays are a gold standard to determine whether composts favor or deter plant growth4. However, plant bioassays are time-consuming (weeks to months) to complete which may be longer than desired and requires more labor to extract plants with roots to quantify severity of root systems. Comparably robust, but quicker (days) assays would be ideal for quality control programs. The goal of this paper is to demonstrate a relatively quick and accurate test to predict suppressive potential of compost. The method was patterned after Alfano et al.5 with two exceptions, compost extracts were diluted and water agar was used in place of potato dextrose agar (PDA). R. solani grows rapidly on simple water agar media whereas PDA promoted growth of bacteria and other fungi that contaminated the culture6.
This plate assay serves as an indicator of suppression that applies to a range of plant pathogens that survive in soil as saprophytes including R. solani7, Alternaria early blights, Fusarium wilt, Phytophthora root rot, and Pythium root rot. The plate competition assay is useful to screen a range of compost products for containing communities of microbes that serve as biological control agents of soil pathogens. The assay was one of the most consistent indicators of disease suppression in commercial compost products6,8. Products were chosen for their variation in recipe, maturity, and production process.

<table>
	<tbody>
		<tr>
			<td>autoclavable narrow-neck glass conical flask</td>
			<td>Fisher Scientific</td>
			<td>10-040D</td>
			<td>125-mL</td>
		</tr>
		<tr>
			<td>dehydrated granulated agar</td>
			<td>Fisher Scientific</td>
			<td>DF0145-17-0</td>
			<td>500 g quantity</td>
		</tr>
		<tr>
			<td>heat resistant gloves</td>
			<td>Fisher Scientific</td>
			<td>MEMGG1314WL</td>
			<td>several brands available</td>
		</tr>
		<tr>
			<td>Parafilm (strips of 2-3 cm wide)</td>
			<td>Fisher Scientific</td>
			<td>PM992 13-374-16</td>
			<td>5 or 10 cm widths work</td>
		</tr>
		<tr>
			<td>disposable polystyrene petri dishes</td>
			<td>Fisher Scientific</td>
			<td>R80116</td>
			<td>comes in sleeves of 20/ea or cases of 500</td>
		</tr>
		<tr>
			<td>dehydrated potato dextrose agar</td>
			<td>Fisher Scientific</td>
			<td>DF0013-15-8</td>
			<td>comes in quantities of 100, 500 and 2000 grams</td>
		</tr>
		<tr>
			<td>benchtop reciprocal shaker</td>
			<td>Thomas Scientific</td>
			<td>1227Y31</td>
			<td>other models will work</td>
		</tr>
		<tr>
			<td>water bath</td>
			<td>ThermoScientific</td>
			<td>S37363</td>
			<td>5L general purpose</td>
		</tr>
		<tr>
			<td>clear ruler, flat, at least 10 cm</td>
			<td>Any</td>
			<td></td>
			<td>use metric rule</td>
		</tr>
		<tr>
			<td>ATCC culture</td>
			<td>American Type Culture Collection</td>
			<td>ATCC 10154</td>
			<td>teleomorph Thanatephorus cucumeris (Frank) (ATCC 10154) or MYA 4031;</td>
		</tr>
		<tr>
			<td>lab tape</td>
			<td>Fisher Scientific</td>
			<td>15935</td>
			<td>autoclavable and removable, 1&#34; wide preferred</td>
		</tr>
		<tr>
			<td>water resistant marker</td>
			<td>office or scientific supply</td>
			<td>Sharpie fine tip</td>
			<td>write sample number on tape</td>
		</tr>
	</tbody>
</table>

a plate competition assay as a quick preliminary assessment of disease suppression

The goal was to develop and optimize a simple, affordable, and effective bioassay to detect disease suppressive ability of a specific compost against soilborne fungus Rhizoctonia solani. R. solani is a pathogen of a wide range of plant hosts worldwide. The fungus survives in soils as a saprophyte and grows rapidly on simple water agar media. The plate assay is a rapid method to compare composts for their ability to slow the growth of R. solani. The assay also correlates well with suppression of other soilborne fungal pathogens that survive as saprophytes in soils such as Alternaria early blights, Fusarium wilt, Phytophthora root rot, and Pythium root rot.

Finished compost should be stable and mature, two terms that are often used interchangeably, so it can be safely packaged and transported, and not cause adverse effects during its end use4. Stability is a resistance to decomposition and is usually determined using indices of microbial activity. General measures of microbial respiration may measure compost stability but not necessarily disease suppression of an aggressive pathogen and saprophyte such as...

Watch this Scientific Journal Video about A Plate Competition Assay As a Quick Preliminary Assessment of Disease Suppression at JoVE.com

A Plate Competition Assay As a Quick Preliminary Assessment of Disease Suppression

Presented is a protocol for a plate competition assay to identify whether a specific compost is likely to contain bacteria and fungi that suppress growth of Rhizoctonia solani.

The goal was to develop and optimize a simple, affordable, and effective bioassay to detect disease suppressive ability of a specific compost against ...

This method can help answer key questions related to the biological control of soilborne plant pathogens. The gold standard for testing materials like compost is to have a plant bioassay to test whether it's toxic to the plants. However, that takes three weeks.This method can be done in about two to three days. The main advantage of this technique is that it is simple, affordable, and effective. This assay is a rapid screening of specific compost to suppress the growth of Rhizoctonia solani.However, this assay can also be used against other soilborne plant pathogens, such as Fusariums, Pythiums, and Phytophthoras. Visual demonstration of this method is critical because it takes care to isolate and maintain a pure culture of a fungus while avoiding contamination. Demonstrating the isolation procedure will be Taylor Readyhough, a graduate student from my laboratory.Emma Wright, an undergraduate student from my laboratory, will demonstrate the competition assay. To begin, sow red radish seeds in soil known to have a history of disease caused by R.solani. After three to four weeks, remove the seedlings from the soil, and rinse them with tap water.Using a razor blade, cut one-centimeter segments of the hypocotyl and root that have a brown color. Then, use flame-sterilized forceps to dip the segments into 10%bleach solution for one minute. After this, rinse the segments in sterile water.Next, use flame-sterilized forceps to transfer the segments to a paper towel. Pat the segments dry, and transfer them to a Petri dish with water agar. Place the Petri dish inside of a container with a lid, and incubate the segments at room temperature.To establish a daughter culture, transfer one of the segments to the center of a fresh plate of potato dextrose agar. After this, autoclave 25-milliliter test tubes containing 10 milliliters of water. Add two 0.5-gram samples of each test sample to a pair of autoclaved test tubes with 10 milliliters of sterile water, and shake the test tubes overnight.After 24 hours, add 1.5 grams of plain agar and 90 milliliters of distilled water to a pair of conical flasks. After autoclaving the flasks, place them into a 45-degree Celsius water bath for 30 minutes. Next, pour the autoclaved reference sample and the living sample into the molten agar.Pour the mixtures from each flask into five Petri dishes. To protect the indigenous microbes, it is important not to add the compost while the agar is too hot. Therefore, allow the agar to cool to 45 degrees Celsius before adding the compost.Using aseptic technique, transfer pieces of R.solani to each pair of sample plates. Then, incubate the plates at room temperature for one to two days. Finally, use a clear, flat ruler and a stereo microscope to measure the radius of the mycelium in each plate to the nearest millimeter.In this protocol, extracts from living composts suppressed R.solani growth significantly more than autoclaved samples, demonstrating that the effect was microbial and not nutrient-based. Suppressiveness is measured as a reduction in growth compared to the autoclaved control. Growth was not affected by the duration of maturation or curing of the compost.Growth was significantly affected by compost method and recipe ingredients, specifically with vermicompost, windrow processes, and recipes with hardwood bark. After its development, this technique may be a candidate for commercial certification of compost for disease-suppressive properties.

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Biology

Application of a C. elegans Dopamine Neuron Degeneration Assay for the Validation of Potential Parkinson's Disease Genes

Improvements to the diagnosis and treatment of Parkinson's disease (PD) are dependent upon knowledge about susceptibility factors that render populations at risk. In the process of attempting to identify novel genetic factors associated with PD, scientists have generated many lists of candidate genes, polymorphisms, and proteins that represent important advances, but these leads remain mechanistically undefined. Our work is aimed toward significantly narrowing such lists by exploiting the advantages of a simple animal model system. While humans have billions of neurons, the microscopic roundworm Caenorhabditis elegans has precisely 302, of which only eight produce dopamine (DA) in hemaphrodites. Expression of a human gene encoding the PD-associated protein, alpha-synuclein, in C. elegans DA neurons results in dosage and age-dependent neurodegeneration.
Worms expressing human alpha-synuclein in DA neurons are isogenic and express both GFP and human alpha-synuclein under the DA transporter promoter (Pdat-1). The presence of GFP serves as a readily visualized marker for following DA neurodegeneration in these animals. We initially demonstrated that alpha-synuclein-induced DA neurodegeneration could be rescued in these animals by torsinA, a protein with molecular chaperone activity 1. Further, candidate PD-related genes identified in our lab via large-scale RNAi screening efforts using an alpha-synuclein misfolding assay were then over-expressed in C. elegans DA neurons. We determined that five of seven genes tested represented significant candidate modulators of PD as they rescued alpha-synuclein-induced DA neurodegeneration 2. Additionally, the Lindquist Lab (this issue of JoVE) has performed yeast screens whereby alpha-synuclein-dependent toxicity is used as a readout for genes that can enhance or suppress cytotoxicity. We subsequently examined the yeast candidate genes in our C. elegans alpha-synuclein-induced neurodegeneration assay and successfully validated many of these targets 3, 4.
Our methodology involves generation of a C. elegans DA neuron-specific expression vector using recombinational cloning of candidate gene cDNAs under control of the Pdat-1 promoter. These plasmids are then microinjected in wild-type (N2) worms, along with a selectable marker for successful transformation. Multiple stable transgenic lines producing the candidate protein in DA neurons are obtained and then independently crossed into the alpha-synuclein degenerative strain and assessed for neurodegeneration, at both the animal and individual neuron level, over the course of aging.

Application of a C. elegans Dopamine Neuron Degeneration Assay for the Validation of Potential Parkinson&#039;s Disease Genes

This video demonstrates how to use C. elegans to assess dopaminergic neuron neurodegeneration as a model for Parkinson's disease. Furthermore, genetic screens are used to identify factors that either enhance degeneration or are neuroprotective.

Improvements to the diagnosis and treatment of Parkinson's disease (PD) are dependent upon knowledge about susceptibility factors that render populations ...

Sigma's Non-specific Protease Activity Assay - Casein as a Substrate

Proteases break peptide bonds. In the lab, it is often necessary to measure and/or compare the activity of proteases. Sigma's non-specific protease activity assay may be used as a standardized procedure to determine the activity of proteases, which is what we do during our quality control procedures. In this assay, casein acts as a substrate. When the protease we are testing digests casein, the amino acid tyrosine is liberated along with other amino acids and peptide fragments. Folin and Ciocalteus Phenol, or Folin's reagent primarily reacts with free tyrosine to produce a blue colored chromophore, which is quantifiable and measured as an absorbance value on the spectrophotometer. The more tyrosine that is released from casein, the more the chromophores are generated and the stronger the activity of the protease. Absorbance values generated by the activity of the protease are compared to a standard curve, which is generated by reacting known quantities of tyrosine with the F-C reagent to correlate changes in absorbance with the amount of tyrosine in micromoles. From the standard curve the activity of protease samples can be determined in terms of Units, which is the amount in micromoles of tyrosine equivalents released from casein per minute.
To view this article in Chinese, <a href="http://jove.com/index/details.stp?ID=910">click here</a>

Sigma&#039;s Non-specific Protease Activity Assay - Casein as a Substrate

Proteases break peptide bonds. In the lab, it is often necessary to measure and/or compare the activity of proteases. Sigma's non-specific protease activity assay may be used as a standardized procedure to determine the activity of proteases.

Proteases break peptide bonds. In the lab, it is often necessary to measure and/or compare the activity of proteases.  Sigma's non-specific protease ...

Use of Rotorod as a Method for the Qualitative Analysis of Walking in Rat

High speed videoanalysis of the details of movement can provide a source of information about qualitative aspects of walking movements. When walking on a rotorod, animals remain in approximately the same place making repetitive movements of stepping. Thus the task provides a rich source of information on the details of foot stepping movements. Subjects were hemi-Parkinson analogue rats, produced by injection of 6-hydroxydopamine (6-OHDA) into the right nigrostriatal bundle to deplete nigrostriatal dopamine (DA). The present report provides a video analysis illustration of animals previously were filmed from frontal, lateral, and posterior views as they walked (15). Rating scales and frame-by-frame replay of the video records of stepping behavior indicated that the hemi-Parkinson rats were chronically impaired in posture and limb use contralateral to the DA-depletion. The contralateral limbs participated less in initiating and sustaining propulsion than the ipsilateral limbs. These deficits secondary to unilateral DA-depletion show that the rotorod provides a use task for the analysis of stepping movements.

The rotorod test is used to assess motor status in the walking movement of hemi-Parkinson analogue rats.

High speed videoanalysis of the details of movement can provide a source of information about qualitative aspects of walking movements. When walking on a ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.
SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.
The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.

We describe here a technique that is now routinely used to isolate stably bound ribosome nascent chain complexes (RNCs). This technique takes advantage of the discovery that a 17 amino acid long SecM "arrest sequence" can halt translation elongation in a prokaryotic (E. coli) system, when inserted into (or fused to the C-terminus) of virtually any protein.

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway ...

Monitoring Intraspecies Competition in a Bacterial Cell Population by Cocultivation of Fluorescently Labelled Strains

Many microorganisms such as bacteria proliferate extremely fast and the populations may reach high cell densities. Small fractions of cells in a population always have accumulated mutations that are either detrimental or beneficial for the cell. If the fitness effect of a mutation provides the subpopulation with a strong selective growth advantage, the individuals of this subpopulation may rapidly outcompete and even completely eliminate their immediate fellows. Thus, small genetic changes and selection-driven accumulation of cells that have acquired beneficial mutations may lead to a complete shift of the genotype of a cell population. Here we present a procedure to monitor the rapid clonal expansion and elimination of beneficial and detrimental mutations, respectively, in a bacterial cell population over time by cocultivation of fluorescently labeled individuals of the Gram-positive model bacterium Bacillus subtilis. The method is easy to perform and very illustrative to display intraspecies competition among the individuals in a bacterial cell population.

Bacteria may accumulate either detrimental or beneficial mutations during their lifetime. In a population of cells individuals that have accumulated beneficial mutations may rapidly outcompete their fellows. Here we present a simple procedure to visualize intraspecies competition in a bacterial cell population over time using fluorescently labeled individuals.&#160;

Many microorganisms such as bacteria proliferate extremely fast and the populations may reach high cell densities. Small fractions of cells in a ...

Xenopus laevis as a Model to Identify Translation Impairment

Protein synthesis is a fundamental process to gene expression impacting diverse biological processes notably adaptation to environmental conditions. The initiation step, which involves the assembly of the ribosomal subunits at the mRNA initiation codon, involved initiation factor including eIF4G1. Defects in this rate limiting step of translation are linked to diverse disorders. To study the potential consequences of such deregulations, Xenopus laevis oocytes constitute an attractive model with high degrees of conservation of essential cellular and molecular mechanisms with human. In addition, during meiotic maturation, oocytes are transcriptionally repressed and all necessary proteins are translated from preexisting, maternally derived mRNAs. This inexpensive model enables exogenous mRNA to become perfectly integrated with an effective translation. Here is described a protocol for assessing translation with a factor of interest (here eIF4G1) using stored maternal mRNA that are the first to be polyadenylated and translated during oocyte maturation as a physiological readout. At first, mRNA synthetized by in vitro transcription of plasmids of interest (here eIF4G1) are injected in oocytes and kinetics of oocyte maturation by Germinal Vesicle Breakdown detection is determined. The studied maternal mRNA target is the serine/threonine-protein-kinase mos. Its polyadenylation and its subsequent translation are investigated together with the expression and phosphorylation of proteins of the mos signaling cascade involved in oocyte maturation. Variations of the current protocol to put forward translational defects are also proposed to emphasize its general applicability. In light of emerging evidence that aberrant protein synthesis may be involved in the pathogenesis of neurological disorders, such a model provides the opportunity to easily assess this impairment and identify new targets.

Xenopus laevis as a Model to Identify Translation Impairment

Protein synthesis control occurs mainly at the translation initiation step, deficiencies in which are linked to diverse disorders. To better understand their etiology, we described here a protocol using Xenopus laevis oocytes assessing the translation of mos transcript in the presence of a mutant of translation initiation factor eIF4G1.

Protein synthesis is a fundamental process to gene expression impacting diverse biological processes notably adaptation to environmental conditions. The ...

qPCRTag Analysis - A High Throughput, Real Time PCR Assay for Sc2.0 Genotyping

The Synthetic Yeast Genome Project (Sc2.0) aims to build 16 designer yeast chromosomes and combine them into a single yeast cell. To date one synthetic chromosome, synIII1, and one synthetic chromosome arm, synIXR2, have been constructed and their in vivo function validated in the absence of the corresponding wild type chromosomes. An important design feature of Sc2.0 chromosomes is the introduction of PCRTags, which are short, re-coded sequences within open reading frames (ORFs) that enable differentiation of synthetic chromosomes from their wild type counterparts. PCRTag primers anneal selectively to either synthetic or wild type chromosomes and the presence/absence of each type of DNA can be tested using a simple PCR assay. The standard readout of the PCRTag assay is to assess presence/absence of amplicons by agarose gel electrophoresis. However, with an average PCRTag amplicon density of one per 1.5 kb and a genome size of ~12 Mb, the completed Sc2.0 genome will encode roughly 8,000 PCRTags. To improve throughput, we have developed a real time PCR-based detection assay for PCRTag genotyping that we call qPCRTag analysis. The workflow specifies 500 nl reactions in a 1,536 multiwell plate, allowing us to test up to 768 PCRTags with both synthetic and wild type primer pairs in a single experiment.

Designer chromosomes of the Synthetic Yeast Genome project, Sc2.0, can be distinguished from their native counterparts using a PCR-based genotyping assay called PCRTagging, which has a presence/absence endpoint. Here we describe a high-throughput real time PCR detection method for PCRTag genotyping.

The Synthetic Yeast Genome Project (Sc2.0) aims to build 16 designer yeast chromosomes and combine them into a single yeast cell. To date one synthetic ...

Time-Lapse Video Microscopy for Assessment of EYFP-Parkin Aggregation as a Marker for Cellular Mitophagy

Time-lapse video microscopy can be defined as the real time imaging of living cells. This technique relies on the collection of images at different time points. Time intervals can be set through a computer interface that controls the microscope-integrated camera. This kind of microscopy requires both the ability to acquire very rapid events and the signal generated by the observed cellular structure during these events. After the images have been collected, a movie of the entire experiment is assembled to show the dynamic of the molecular events of interest. Time-lapse video microscopy has a broad range of applications in the biomedical research field and is a powerful and unique tool for following the dynamics of the cellular events in real time. Through this technique, we can assess cellular events such as migration, division, signal transduction, growth, and death. Moreover, using fluorescent molecular probes we are able to mark specific molecules, such as DNA, RNA or proteins and follow them through their molecular pathways and functions. Time-lapse video microscopy has multiple advantages, the major one being the ability to collect data at the single-cell level, that make it a unique technology for investigation in the field of cell biology. However, time-lapse video microscopy has limitations that can interfere with the acquisition of high quality images. Images can be compromised by both external factors; temperature fluctuations, vibrations, humidity and internal factors; pH, cell motility. Herein, we describe a protocol for the dynamic acquisition of a specific protein, Parkin, fused with the enhanced yellow fluorescent protein (EYFP) in order to track the selective removal of damaged mitochondria, using a time-lapse video microscopy approach.

Herein, we describe in detail a time-lapse video microscopy approach to measuring the temporal recruitment of EYFP-Parkin during the selective removal of damaged mitochondria. This dynamic process of EYFP-Parkin-dependent removal of damaged mitochondria can be used as an indicator of cellular health under different experimental conditions.

Time-lapse video microscopy can be defined as the real time imaging of living cells. This technique relies on the collection of images at different time ...

Deferred Growth Inhibition Assay to Quantify the Effect of Bacteria-derived Antimicrobials on Competition

Competitive exclusion can occur in microbial communities when, for example, an inhibitor-producing strain outcompetes its competitor for an essential nutrient or produces antimicrobial compounds that its competitor is not resistant to. Here we describe a deferred growth inhibition assay, a method for assessing the ability of one bacterium to inhibit the growth of another through the production of antimicrobial compounds or through competition for nutrients. This technique has been used to investigate the correlation of nasal isolates with the exclusion of particular species from a community. This technique can also be used to screen for lantibiotic producers or potentially novel antimicrobials. The assay is performed by first culturing the test inhibitor-producing strain overnight on an agar plate, then spraying over the test competitor strain and incubating again. After incubation, the extent of inhibition can be measured quantitatively, through the size of the zone of clearing around the inhibitor-producing strain, and qualitatively, by assessing the clarity of the inhibition zone. Here we present the protocol for the deferred inhibition assay, describe ways to minimize variation between experiments, and define a clarity scale that can be used to qualitatively assess the degree of inhibition.

The deferred growth inhibition assay can be used to assess the competition effect by one bacterial isolate on another. Inhibition is quantified by measuring the zone of clearing around the inhibitor-producing isolate, or qualitatively assessed by determining the visible extent of inhibition.

Competitive exclusion can occur in microbial communities when, for example, an inhibitor-producing strain outcompetes its competitor for an essential ...