We thank Jamie Calma for testing the effect of media volume on disease or resistance outcomes. We thank Dr. Ma&#235;l Baudin and Dr. Karl J. Scheiber from the Lewis Lab for providing constructive comments and suggestions on the manuscript. Research on plant immunity in the Lewis laboratory was supported by the USDA ARS 2030-21000-046-00D and 2030-21000-050-00D (JDL), and the NSF Directorate for Biological Sciences IOS-1557661 (JDL).

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The authors have nothing to disclose.

A protocol for flood inoculation with PstDC3000 or Pst19 optimized to detect resistance to these bacterial strains in tomato seedlings is described. There are several critical parameters for optimal results in the seedling resistance assay, including bacterial concentration and surfactant concentration, which were empirically determined22. For PstDC3000, the optical density was optimized to achieve complete survival on a resistant cultivar containing the Pto/Prf...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/60805">High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay</a>. The Introduction, Protocol, Representative Results and Discussion&#160;sections were&#160;updated.

Erratum: High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

Pseudomonas syringae is a Gram-negative pathogenic bacterium that infects a wide range of plant hosts. Bacteria enter the host plant through the stomata or physical wounds and proliferate in the apoplast1. Plants have evolved a two-tiered immune response to protect against infection by bacterial pathogens. The first level occurs at the plant cell surface, where pattern recognition receptors on the plant cell membrane perceive highly conserved pathogen-associated molecular patterns (PAMPs) in a process called PAMP-triggered immunity (PTI)2. During this process, the host plant upregulates defense response pathways, including deposition of callose to the cell wall, closure of stomata, production of reactive oxygen species, and induction of pathogenesis-related genes.
Bacteria can overcome PTI by utilizing a type III secretion system to deliver proteins, called effectors, directly into the plant cell3. Effector proteins commonly target components of PTI and promote pathogen virulence4. The second tier of plant immunity occurs within the plant cell upon recognition of the effector proteins. This recognition is dependent on resistance genes, which encode nucleotide-binding site leucine-rich repeat containing receptors (NLRs). NLRs are capable of either recognizing effectors directly or recognizing their activity on a virulence target or decoy5. They then trigger a secondary immune response in a process called effector-triggered immunity (ETI), which is often associated with a hypersensitive response (HR), a form of localized cell death at the site of infection6. In contrast to gene-for-gene resistance associated with ETI, plants can exhibit quantitative partial resistance, which is dependent on the contribution of multiple genes7.
P. syringae pv. tomato (Pst) is the causal agent of bacterial speck on tomato and is a persistent agricultural problem. Predominant strains in the field have typically been Pst race 0 strains that express either or both of the type III effectors AvrPto and AvrPtoB. DC3000 (PstDC3000) is a representative race 0 strain and a model pathogen that can cause bacterial speck in tomato. To combat bacterial speck disease, breeders introgressed the Pto [P. syringae pv. tomato]/Prf [Pto resistance and fenthion sensitivity] gene cluster from the wild tomato species Solanum pimpinellifolium into modern cultivars8,9. The Pto gene encodes a serine-threonine protein kinase that, together with the Prf NLR, confer resistance to PstDC3000 via recognition of the effectors AvrPto and AvrPtoB10,11,12,13,14. However, this resistance is ineffective against emerging race 1 strains, allowing for their rapid and aggressive spread in recent years15,16. Race 1 strains evade recognition by the Pto/Prf cluster, because AvrPto is either lost or mutated in these strains, and AvrPtoB appears to accumulate minimally15,17,18.
Wild tomato populations are important reservoirs of natural variation for Pst resistance and have previously been used to identify potential resistance loci19,20,21. However, current screens for pathogen resistance utilize 4&#8211;5-week-old adult plants20,21. Therefore, they are limited by growth time, growth chamber space, and relatively small sample sizes. To address the limitations of conventional approaches, we developed a high-throughput tomato P. syringae resistance assay using 10-day-old tomato seedlings22. This approach offers several advantages over using adult plants: namely, shorter growth time, reduced space requirements, and higher throughput. Furthermore, we have demonstrated that this approach faithfully recapitulates disease resistance phenotypes observed in adult plants22.
In the seedling flood assay described in this protocol, tomato seedlings are grown on Petri dishes of sterile Murashige and Skoog (MS) media for 10 days and then are flooded with an inoculum containing the bacteria of interest and a surfactant. Following flooding, seedlings can be quantitatively evaluated for disease resistance via bacterial growth assays. Additionally, seedling survival or death can act as a discrete resistance or disease phenotype 7&#8211;14 days after flooding. This approach offers a high-throughput alternative for screening large numbers of wild tomato accessions for resistance to Pst race 1 strains, such as Pst strain 19 (Pst19), and can easily be adapted to other bacterial strains of interest.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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			<td>3M Tape Micropore 1/2&#34; x 10 YD CS 240 (1.25 cm x 9.1 m)</td>
			<td>VWR International</td>
			<td>56222-182</td>
			<td></td>
		</tr>
		<tr>
			<td>3mm borosilicate glass beads</td>
			<td>Friedrich &#38; Dimmock</td>
			<td>GB3000B</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacto peptone</td>
			<td>BD</td>
			<td>211677</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacto agar</td>
			<td>BD</td>
			<td>214010</td>
			<td></td>
		</tr>
		<tr>
			<td>Biophotometer Plus</td>
			<td>Eppendorf</td>
			<td>E952000006</td>
			<td></td>
		</tr>
		<tr>
			<td>Biosafety cabinet, class II type A2</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BRAND Disposable Plastic Cuvettes, Polystyrene</td>
			<td>VWR International</td>
			<td>47744-642</td>
			<td></td>
		</tr>
		<tr>
			<td>Chenille Kraft Flat Wood Toothpicks</td>
			<td>VWR International</td>
			<td>500029-808</td>
			<td></td>
		</tr>
		<tr>
			<td>cycloheximide</td>
			<td>Research Products International</td>
			<td>C81040-5.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Dibasic potassium phosphate anhydrous, ACS grade</td>
			<td>Fisher Scientific</td>
			<td>P288-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylformamide</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting microscope (Magnification of at least 10x)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol - 190 Proof</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon polystyrene 96 well microplates, flat-bottom</td>
			<td>Fisher Scientific</td>
			<td>08-772-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Alcohol Burner Wick</td>
			<td>Fisher Scientific</td>
			<td>S41898A / No. W-125</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Alcohol Burners</td>
			<td>Fisher Scientific</td>
			<td>S41898 / No. BO125</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol ACS reagent</td>
			<td>VWR International</td>
			<td>EMGX0185-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimberly-Clark&#8482; Kimtech Science&#8482; Kimwipes&#8482; Delicate Task Wipers</td>
			<td>Fisher Scientific</td>
			<td>06-666-A</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride, ACS grade</td>
			<td>VWR International</td>
			<td>97061-356</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate heptahydrate, ACS grade</td>
			<td>VWR International</td>
			<td>97062-130</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes, 1.5 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes, 2.2 mL</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mini Beadbeater-96, 115 volt</td>
			<td>Bio Spec Products Inc.</td>
			<td>1001</td>
			<td></td>
		</tr>
		<tr>
			<td>Murashige &#38; Skoog, Basal Salts</td>
			<td>Caisson Laboratories, Inc.</td>
			<td>MSP01-50LT</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipet-Lite XLS LTS 8-CH Pipet 20-200uL</td>
			<td>Rainin</td>
			<td>L8-200XLS</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipet-Lite XLS LTS 8-CH Pipet 2-20uL</td>
			<td>Rainin</td>
			<td>L8-20XLS</td>
			<td></td>
		</tr>
		<tr>
			<td>Polystyrene 100mm x 25mm sterile petri dish</td>
			<td>VWR International</td>
			<td>89107-632</td>
			<td></td>
		</tr>
		<tr>
			<td>Polystyrene 150mm x 15mm sterile petri dish</td>
			<td>Fisher Scientific</td>
			<td>FB08-757-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Polystyrene 150x15mm sterile petri dish</td>
			<td>Fisher Scientific</td>
			<td>08-757-148</td>
			<td></td>
		</tr>
		<tr>
			<td>Pure Bright Germicidal Ultra Bleach 5.7% Available Chlorine (defined as 100% bleach)</td>
			<td>Staples</td>
			<td>1013131</td>
			<td></td>
		</tr>
		<tr>
			<td>Rifampicin</td>
			<td>Gold Biotechnology</td>
			<td>R-120-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Silwet L-77 (non-ionic organosilicone surfactant co-polymer C13H34O4Si3 surfactant)</td>
			<td>Fisher Scientific</td>
			<td>NCO138454</td>
			<td></td>
		</tr>
		<tr>
			<td>Tips LTS 20 &#956;L 960/10 GPS-L10</td>
			<td>Rainin</td>
			<td>17005091</td>
			<td></td>
		</tr>
		<tr>
			<td>Tips LTS 250 &#956;L 960/10 GPS-L250</td>
			<td>Rainin</td>
			<td>17005093</td>
			<td></td>
		</tr>
		<tr>
			<td>VWR dissecting forceps fine tip, 4.5&#34;</td>
			<td>VWR International</td>
			<td>82027-386</td>
			<td></td>
		</tr>
	</tbody>
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high-throughput identification of resistance to pseudomonas syringae pv. tomato in tomato using seedling flood assay

Tomato is an agronomically important crop that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck disease. The tomato-P. syringae pv. tomato pathosystem is widely used to dissect the genetic basis of plant innate responses and disease resistance. While disease was successfully managed for many decades through the introduction of the Pto/Prf gene cluster from Solanum pimpinellifolium into cultivated tomato, race 1 strains of P. syringae have evolved to overcome resistance conferred by the Pto/Prf gene cluster and occur worldwide.
Wild tomato species are important reservoirs of natural diversity in pathogen recognition, because they evolved in diverse environments with different pathogen pressures. In typical screens for disease resistance in wild tomato, adult plants are used, which can limit the number of plants that can be screened due to their extended growth time and greater growth space requirements. We developed a method to screen 10-day-old tomato seedlings for resistance, which minimizes plant growth time and growth chamber space, allows a rapid turnover of plants, and allows large sample sizes to be tested. Seedling outcomes of survival or death can be treated as discrete phenotypes or on a resistance scale defined by amount of new growth in surviving seedlings after flooding. This method has been optimized to screen 10-day-old tomato seedlings for resistance to two P. syringae strains and can easily be adapted to other P. syringae strains.

Detection of PtoR-mediated immunity in cultivars and isogenic lines using the seedling resistance assay 
Figure 5 shows representative results for Moneymaker-PtoR and Moneymaker-PtoS cultivars 7&#8211;10 days after flooding with PstDC3000. Prior to infection, 10-day-old seedlings displayed fully emerged and expanded cotyledons and emerging first true leaves. The seedlings were flooded with 10 mM MgCl2 + 0.015% surfactant as...

Watch this Scientific Journal Video about High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay at JoVE.com

High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

The seedling flood assay facilitates rapid screening of wild tomato accessions for the resistance to the Pseudomonas syringae bacterium. This assay, used in conjunction with the seedling bacterial growth assay, can assist in further characterizing the underlying resistance to the bacterium, and can be used to screen mapping populations to determine the genetic basis of resistance.

High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

Tomato is an agronomically important crop that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck disease. ...

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Research

JoVE Journal

Bioengineering

9.4K Views.  University of California, Berkeley. The seedling flood assay facilitates rapid screening of wild tomato accessions for the resistance to the Pseudomonas syringae bacterium. This assay, used in conjunction with the seedling bacterial growth assay, can assist in further characterizing the underlying resistance to the bacterium, and can be used to screen mapping populations to determine the genetic basis of resistance.

Video: High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

Cell-based Calcium Assay for Medium to High Throughput Screening of TRP Channel Functions using FlexStation 3

The Molecular Devices' FlexStation 3 is a benchtop multi-mode microplate reader capable of automated fluorescence measurement in multi-well plates. It is ideal for medium- to high-throughput screens in academic settings. It has an integrated fluid transfer module equipped with a multi-channel pipetter and the machine reads one column at a time to monitor fluorescence changes of a variety of fluorescent reagents. For example, FlexStation 3 has been used to study the function of Ca2+-permeable ion channels and G-protein coupled receptors by measuring the changes of intracellular free Ca2+ levels. Transient receptor potential (TRP) channels are a large family of nonselective cation channels that play important roles in many physiological and pathophysiological functions. Most of the TRP channels are calcium permeable and induce calcium influx upon activation. In this video, we demonstrate the application of FlexStation 3 to study the pharmacological profile of the TRPA1 channel, a molecular sensor for numerous noxious stimuli. HEK293 cells transiently or stably expressing human TRPA1 channels, grown in 96-well plates, are loaded with a Ca2+-sensitive fluorescent dye, Fluo-4, and real-time fluorescence changes in these cells are measured before and during the application of a TRPA1 agonist using the FLEX mode of the FlexStation 3. The effect of a putative TRPA1 antagonist was also examined. Data are transferred from the SoftMax Pro software to construct concentration-response relationships of TRPA1 activators and inhibitors.

This video provides a detailed protocol for studying the pharmacological profile of human TRPA1 channels using FlexStation 3. The protocol covers details of cell preparation, dye loading and operation of the microplate reader, FlexStation 3.

The Molecular Devices' FlexStation 3 is a benchtop multi-mode microplate reader capable of automated fluorescence measurement in multi-well plates.  It is ...

Polymer Microarrays for High Throughput Discovery of Biomaterials

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a combinatorial library of materials to be screened in a parallel, high throughput format1. Herein is described the formation and characterization of a polymer microarray using an on-chip photopolymerization technique 2. This involves mixing monomers at varied ratios to produce a library of monomer solutions, transferring the solution to a glass slide format using a robotic printing device and curing with UV irradiation. This format is readily amenable to many biological assays, including stem cell attachment and proliferation, cell sorting and low bacterial adhesion, allowing the ready identification of 'hit' materials that fulfill a specific biological criterion3-5. Furthermore, the use of high throughput surface characterization (HTSC) allows the biological performance to be correlated with physio-chemical properties, hence elucidating the biological-material interaction6. HTSC makes use of water contact angle (WCA) measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In particular, ToF-SIMS provides a chemically rich analysis of the sample that can be used to correlate the cell response with a molecular moiety. In some cases, the biological performance can be predicted from the ToF-SIMS spectra, demonstrating the chemical dependence of a biological-material interaction, and informing the development of hit materials5,3.

A description of the formation of a polymer microarray using an on-chip photopolymerization technique. The high throughput surface characterization using atomic force microscopy, water contact angle measurements, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry and a cell attachment assay is also described.

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a ...

High-throughput Protein Expression Generator Using a Microfluidic Platform

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and high-fidelity measurements of large systems. Microfluidics promises to fulfill many of these requirements, such as performing high-throughput screening experiments on-chip, encompassing biochemical, biophysical, and cell-based assays1. Since the early days of microfluidics devices, this field has drastically evolved, leading to the development of microfluidic large-scale integration2,3. This technology allows for the integration of thousands of micromechanical valves on a single device with a postage-sized footprint (Figure 1). We have developed a high-throughput microfluidic platform for generating in vitro expression of protein arrays (Figure 2) named PING (Protein Interaction Network Generator). These arrays can serve as a template for many experiments such as protein-protein 4, protein-RNA5 or protein-DNA6 interactions.
The device consist of thousands of reaction chambers, which are individually programmed using a microarrayer. Aligning of these printed microarrays to microfluidics devices programs each chamber with a single spot eliminating potential contamination or cross-reactivity Moreover, generating microarrays using standard microarray spotting techniques is also very modular, allowing for the arraying of proteins7, DNA8, small molecules, and even colloidal suspensions. The potential impact of microfluidics on biological sciences is significant. A number of microfluidics based assays have already provided novel insights into the structure and function of biological systems, and the field of microfluidics will continue to impact biology.

We present a microfluidic approach for the expression of protein arrays. The device consists of thousands of reaction chambers controlled by micro-mechanical valves. The microfluidic device is mated to a microarray-printed gene library. These genes are then transcribed and translated on-chip, resulting in a protein array ready for experimental use.

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and ...

High-throughput Synthesis of Carbohydrates and Functionalization of Polyanhydride Nanoparticles

Transdisciplinary approaches involving areas such as material design, nanotechnology, chemistry, and immunology have to be utilized to rationally design efficacious vaccines carriers. Nanoparticle-based platforms can prolong the persistence of vaccine antigens, which could improve vaccine immunogenicity1. Several biodegradable polymers have been studied as vaccine delivery vehicles1; in particular, polyanhydride particles have demonstrated the ability to provide sustained release of stable protein antigens and to activate antigen presenting cells and modulate immune responses2-12.
The molecular design of these vaccine carriers needs to integrate the rational selection of polymer properties as well as the incorporation of appropriate targeting agents. High throughput automated fabrication of targeting ligands and functionalized particles is a powerful tool that will enhance the ability to study a wide range of properties and will lead to the design of reproducible vaccine delivery devices.
The addition of targeting ligands capable of being recognized by specific receptors on immune cells has been shown to modulate and tailor immune responses10,11,13 C-type lectin receptors (CLRs) are pattern recognition receptors (PRRs) that recognize carbohydrates present on the surface of pathogens. The stimulation of immune cells via CLRs allows for enhanced internalization of antigen and subsequent presentation for further T cell activation14,15. Therefore, carbohydrate molecules play an important role in the study of immune responses; however, the use of these biomolecules often suffers from the lack of availability of structurally well-defined and pure carbohydrates. An automation platform based on iterative solution-phase reactions can enable rapid and controlled synthesis of these synthetically challenging molecules using significantly lower building block quantities than traditional solid-phase methods16,17.
Herein we report a protocol for the automated solution-phase synthesis of oligosaccharides such as mannose-based targeting ligands with fluorous solid-phase extraction for intermediate purification. After development of automated methods to make the carbohydrate-based targeting agent, we describe methods for their attachment on the surface of polyanhydride nanoparticles employing an automated robotic set up operated by LabVIEW as previously described10. Surface functionalization with carbohydrates has shown efficacy in targeting CLRs10,11 and increasing the throughput of the fabrication method to unearth the complexities associated with a multi-parametric system will be of great value (Figure 1a).

In this article, a high throughput method is presented for the synthesis of oligosaccharides and their attachment to the surface of polyanhydride nanoparticles for further use in targeting specific receptors on antigen presenting cells.

Transdisciplinary approaches involving areas such as material design, nanotechnology, chemistry, and immunology have to be utilized to rationally design ...

Use of a High-throughput In Vitro Microfluidic System to Develop Oral Multi-species Biofilms

There are few high-throughput in vitro systems which facilitate the development of multi-species biofilms that contain numerous species commonly detected within in vivo oral biofilms. Furthermore, a system that uses natural human saliva as the nutrient source, instead of artificial media, is particularly desirable in order to support the expression of cellular and biofilm-specific properties that mimic the in vivo communities. We describe a method for the development of multi-species oral biofilms that are comparable, with respect to species composition, to supragingival dental plaque, under conditions similar to the human oral cavity. Specifically, this methods article will describe how a commercially available microfluidic system can be adapted to facilitate the development of multi-species oral biofilms derived from and grown within pooled saliva. Furthermore, a description of how the system can be used in conjunction with a confocal laser scanning microscope to generate 3-D biofilm reconstructions for architectural and viability analyses will be presented. Given the broad diversity of microorganisms that grow within biofilms in the microfluidic system (including Streptococcus, Neisseria, Veillonella, Gemella, and Porphyromonas), a protocol will also be presented describing how to harvest the biofilm cells for further subculture&#160;or DNA extraction and analysis. The limits of both the microfluidic biofilm system and the current state-of-the-art data analyses will be addressed. Ultimately, it is envisioned that this article will provide a baseline technique that will improve the study of oral biofilms and aid in the development of additional technologies that can be integrated with the microfluidic platform.

Use of a High-throughput In Vitro Microfluidic System to Develop Oral Multi-species Biofilms

The goal of this methods paper is to describe the use of a microfluidic system for the development of multi-species biofilms that contain species typically identified in human supragingival dental plaque.&#160;Methods to describe biofilm architecture, biofilm viability, and an approach to harvest biofilm for culture-dependent or culture-independent analyses are highlighted.

There are few high-throughput in vitro systems which facilitate the development of multi-species biofilms that contain numerous species commonly detected ...

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

Using Tomoauto: A Protocol for High-throughput Automated Cryo-electron Tomography

Cryo-electron tomography (Cryo-ET) is a powerful three-dimensional (3-D) imaging technique for visualizing macromolecular complexes in their native context at a molecular level. The technique involves initially preserving the sample in its native state by rapidly freezing the specimen in vitreous ice, then collecting a series of micrographs from different angles at high magnification, and finally computationally reconstructing a 3-D density map. The frozen-hydrated specimen is extremely sensitive to the electron beam and so micrographs are collected at very low electron doses to limit the radiation damage. As a result, the raw cryo-tomogram has a very low signal to noise ratio characterized by an intrinsically noisy image. To better visualize subjects of interest, conventional imaging analysis and sub-tomogram averaging in which sub-tomograms of the subject are extracted from the initial tomogram and aligned and averaged are utilized to improve both contrast and resolution. Large datasets of tilt-series are essential to understanding and resolving the complexes at different states, conditions, or mutations as well as obtaining a large enough collection of sub-tomograms for averaging and classification. Collecting and processing this data can be a major obstacle preventing further analysis. Here we describe a high-throughput cryo-ET protocol based on a computer-controlled 300kV cryo-electron microscope, a direct detection device (DDD) camera and a highly effective, semi-automated image-processing pipeline software wrapper library tomoauto developed in-house. This protocol has been effectively utilized to visualize the intact type III secretion system (T3SS) in Shigella flexneri minicells. It can be applicable to any project suitable for cryo-ET.

We present a protocol on how to utilize high-throughput cryo-electron tomography to determine high resolution in situ structures of molecular machines. The protocol permits large amounts of data to be processed, avoids common bottlenecks and reduces resource downtime, allowing the user to focus on important biological questions.

Cryo-electron tomography (Cryo-ET) is a powerful three-dimensional (3-D) imaging technique for visualizing macromolecular complexes in their native ...

High-throughput Identification of Bacteria Repellent Polymers for Medical Devices

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as contributing to antimicrobial resistance. One possible avenue for the reduction of device-associated infections is the identification of bacteria-repellent polymer coatings for these devices, which would prevent bacterial binding at the initial attachment step. A method for the identification of such repellent polymers, based on the parallel screening of hundreds of polymers using a microarray, is described here. This high-throughput method resulted in the identification of a range of promising polymers that resisted binding of various clinically relevant bacterial species individually and also as multi-species communities. One polymer, PA13 (poly(methylmethacrylate-co-dimethylacrylamide)), demonstrated significant reduction in attachment of a number of hospital isolates when coated onto two commercially available central venous catheters. The method described could be applied to identify polymers for a wide range of applications in which modification of bacterial attachment is important.

A high-throughput microarray method for the identification of polymers which reduce bacterial surface binding on medical devices is described.

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as ...

Process Optimization using High Throughput Automated Micro-Bioreactors in Chinese Hamster Ovary Cell Cultivation

Optimization of bioprocesses to increase the yield of desired products is of importance in the biopharmaceutical industry. This can be achieved by strain selection and by developing bioprocess parameters. Shake flasks have been used for this purpose. They, however, lack the capability to control the process parameters such as pH and dissolved oxygen (DO). This limitation can be overcome with the help of an automated micro-bioreactor. These bioreactors mimic cultivation at a larger scale. One of the major advantages of this system is the integration of the Design of Experiment (DOE) in the software. This integration enables establishing a design where multiple process parameters can be varied simultaneously. The critical process parameters and optimum bioprocess conditions can be analyzed within the software. The focus of the work presented here is to introduce the user to the steps involved in process design in the software and incorporation of the DOE within the cultivation run.

Here, we present a detailed procedure to run a Design of Experiment in an automated micro-bioreactor followed by cell harvest and protein quantification using a Protein A column.

Optimization of bioprocesses to increase the yield of desired products is of importance in the biopharmaceutical industry. This can be achieved by strain ...

High Throughput Yeast Strain Phenotyping with Droplet-Based RNA Sequencing

The powerful tools available to edit yeast genomes have made this microbe a valuable platform for engineering. While it is now possible to construct libraries of millions of genetically distinct strains, screening for a desired phenotype remains a significant obstacle. With existing screening techniques, there is a tradeoff between information output and throughput, with high-throughput screening typically being performed on one product of interest. Therefore, we present an approach to accelerate strain screening by adapting single cell RNA sequencing to isogenic picoliter colonies of genetically engineered yeast strains. To address the unique challenges of performing RNA sequencing on yeast cells, we culture isogenic yeast colonies within hydrogels and spheroplast prior to performing RNA sequencing. The RNA sequencing data can be used to infer yeast phenotypes and sort out engineered pathways. The scalability of our method addresses a critical obstruction in microbial engineering.

A bottleneck in the &#8216;design-build-test&#8217; cycle of microbial engineering is the speed at which we can perform functional screens of strains. We describe a high-throughput method for strain screening applied to hundreds to thousands of yeast cells per experiment that utilizes droplet-based RNA sequencing.

The powerful tools available to edit yeast genomes have made this microbe a valuable platform for engineering. While it is now possible to construct ...