Name: a rapid image-based bacterial virulence assay using amoeba
Uploaded: 2018-06-27T15:00:00
Description: Watch this Scientific Journal Video about A Rapid Image-based Bacterial Virulence Assay Using Amoeba at JoVE.com

KP et AS a écrit et révisé le manuscrit. KP effectué les expériences et l’analyse. Ce travail a été soutenu par le National Institutes of Health (NIH) Bourse de Transition de carrière (K22AI112816) à As.

Toutes les procédures expérimentales ont été effectuées à l’Université de Californie, Irvine.
1. tampons et Solutions
<ol><li>Préparer, lysogénie bouillon (LB) dans un flacon de verre de 1 L en ajoutant 25 g de mélange de LB-Miller dans 1 L d’eau bidistillée (ddH2O). Pour boîtes de Pétri, ajouter une supplémentaire 20 g d’agar. Autoclave pour stériliser. Verser 25 mL de milieu gélosé fondu dans Pétri de 10 cm de diamètre et laisser pour solidifier à temp?...

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+pathogen+Pseudomonas+aeruginosa+utilizes+conserved+virulence+pathways+to+infect+the+social+amoeba+Dictyostelium+discoideum.">The human pathogen Pseudomonas aeruginosa utilizes conserved virulence pathways to infect the social amoeba Dictyostelium discoideum.</a> Proceedings of the National Academy of Sciences U S A. 99 (5), 3159-3164 (2002).</li><li>Cosson, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pseudomonas+aeruginosa+Virulence+Analyzed+in+a+Dictyostelium+discoideum+Host+System.">Pseudomonas aeruginosa Virulence Analyzed in a Dictyostelium discoideum Host System.</a> Journal of Bacteriology. 184 (11), 3027-3033 (2002).</li><li>Pukatzki, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+conserved+bacterial+protein+secretion+system+in+Vibrio+cholerae+using+the+Dictyostelium+host+model+system.">Identification of a conserved bacterial protein secretion system in Vibrio cholerae using the Dictyostelium host model system.</a> Proceedings of the National Academy of Sciences U S A. 103 (5), 1528-1533 (2006).</li><li>Steinert, M., Heuner, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dictyostelium+as+host+model+for+pathogenesis.">Dictyostelium as host model for pathogenesis.</a> Cellular Microbiology. 7 (3), 307-314 (2005).</li><li>Hagele, S., Kohler, R., Merkert, H., Schleicher, M., Hacker, J., Steinert, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dictyostelium+discoideum:+a+new+host+model+system+for+intracellular+pathogens+of+the+genus+Legionella.">Dictyostelium discoideum: a new host model system for intracellular pathogens of the genus Legionella.</a> Cellular Microbiology. 2 (2), 165-171 (2000).</li><li>Matz, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pseudomonas+aeruginosa+uses+type+III+secretion+system+to+kill+biofilm-associated+amoebae.">Pseudomonas aeruginosa uses type III secretion system to kill biofilm-associated amoebae.</a> ISME Journal. 2 (8), 843-852 (2008).</li><li>Hauser, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+type+III+secretion+system+of+Pseudomonas+aeruginosa:+infection+by+injection.">The type III secretion system of Pseudomonas aeruginosa: infection by injection.</a> Nature Reviews Microbiology. 7 (9), 654-665 (2009).</li><li>Moore, P. L., MacCoubrey, I. C., Haugland, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+pH+insensitive,+two+color+fluorescence+viability+(cytotoxicity)+assay.">A rapid pH insensitive, two color fluorescence viability (cytotoxicity) assay.</a> Journal of Cell Biology. 111, 58 (1990).</li><li>Kaneshiro, E. S., Wyder, M. A., Wu, Y. -. P., Cushion, M. 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A., Noack, C., Boehringer, D., Biermann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Staining+of+fluorogold-prelabeled+retinal+ganglion+cells+with+calcein-AM:+A+new+method+for+assessing+cell+vitality.">Staining of fluorogold-prelabeled retinal ganglion cells with calcein-AM: A new method for assessing cell vitality.</a> Journal of Neuroscience Methods. 192 (2), 233-239 (2010).</li><li>Witkin, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inherited+Differences+in+Sensitivity+to+Radiation+in+Escherichia+Coli.">Inherited Differences in Sensitivity to Radiation in Escherichia Coli.</a> Proceedings of the National Academy of Sciences U S A. 32 (3), 59-68 (1946).</li><li>Loomis, W. 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Ce protocole décrit une méthode rapide et quantitative pour doser la virulence chez P. aeruginosa. Ce protocole peut être testé avec d’autres bactéries. Toutefois, il est important de garder à l’esprit que le milieu de croissance doit être compatible avec les conditions de croissance d’amibe. En particulier, nous avons optimisé le protocole en utilisant PS:DB comme le milieu de croissance bactérienne. Si les autres médias sont utilisés, il peut être nécessaire d’effectuer un contrôle de cro...

Infection bactérienne est l’une des principales causes de mortalité chez l’homme et les animaux1,2. La capacité de mesurer la virulence des bactéries dans des cultures ou des biofilms est importante dans les milieux de soins de santé et de la recherche. Nous décrivons ici une méthode relativement simple, rapide et polyvalent pour quantifier la virulence bactérienne. L’organisme eucaryote Dictyostelium discoideum (amibes) est utilisé comme organisme modèle hôte. D. discoideum a été utilisé comme un hôte pour identifier les facteurs de virulence Pseudomonas aeruginosa (P. aeruginosa)3,4,5 et autres bactéries6,7 ,8 et est susceptibles d’être en grande partie les mêmes facteurs de virulence qui tuent les cellules mammifères, y compris le type III sécrétion9,10. Précédents essais de virulence à l’aide de d. discoideum ont impliqué une exposition prolongée des bactéries aux cellules de d. discoideum au cours des heures3,4,5. Le protocole, ici, présente une méthode rapide de détermination de virulence à l’aide de cette amibe. Ce protocole (Figure 1) décrit comment faire pour : (1) poussent les amibes axéniques (en l’absence de bactéries), (2) développer des bactéries pour le dosage, (3) préparer des bactéries et cellules de l’hôte pour la microscopie, (4) effectuent la microscopie à épifluorescence et (5) analysent amibe fluorescence.
Amibes sont initialement striées sur des stocks congelés et cultivés sur une pelouse d' Escherichia coli (e. coli), où les amibes produisent des spores. Ces spores sont cueillies et inoculés dans un milieu enrichi de croissance axénique. Les amibes sont maintenues grâce à une croissance axénique dans des conditions nutritives jusqu'à ce qu’ils sont prêts à être mélangés avec les bactéries pour l’évaluation de la virulence bactérienne. La survie ou la mort des amibes est quantifiée par la mesure de la fluorescence de calcéine-acétoxyméthyl (calcéine-AM), qui est clivé par les estérases intracellulaires et, ainsi, activé pour fluorescence11,12. Direct amibes présentent peu ou pas de fluorescence qu’a souligné et cellules mourantes réagissent en intensément. Ce résultat est dû à l’incorporation de petite ou pas de calcéine-AM dans les amibes sains et l’incorporation et le clivage du substrat dans les amibes stressé13. Ce comportement diffère notamment de fluorescence de calcéine-AM dans les cellules de mammifères11,14,15,16.
Les bactéries qui seront évaluées pour la virulence sont cultivés séparément. Ici, nous décrivons comment mesurer la virulence de l’agent pathogène opportuniste de P. aeruginosa et détailler comment quantifier la virulence des planctonique (natation) et attaché à la surface de certaines sous-populations. Ce protocole peut être adapté pour tester la virulence d’autres bactéries. Dans la section résultats de représentant, nous montrons que la virulence est activé dans les cellules attachées à la surface et est faible dans les cellules planctoniques, qui a été rapporté précédemment13. Activé par virulence rattaché au surface P. aeruginosa tue amibes alors que non virulentes cellules planctoniques sont consommés par les amibes. Si la virulence des bactéries planctoniques est uniquement être analysée, les bactéries peuvent être cultivées dans des tubes à culture ordinaire plutôt que d’utiliser des boîtes de Pétri comme décrit dans le protocole.
La croissance des amibes et P. aeruginosa cultures doit être coordonnée, tel que les cultures P. aeruginosa atteint la phase de croissance prévue, tandis que les amibes sont de plus en plus à l’état stable dans des conditions de nutriments. Cette condition nécessite généralement des cultures d’amibes à diluer au moins 1 jour avant lorsqu’ils sont mélangés avec des bactéries. Les amibes et bactéries sont immobilisées à l’aide de tampons de gélose, sont conjointement mis en incubation pendant 1 h et imagés à l’aide d’une faible résolution (10 X, ouverture numérique 0,3) filtres de protéine de fluorescence objective, verte (GFP) et une caméra d’imagerie. Analyse peut être effectuée à l’aide disponible gratuitement logiciel ImageJ ou personnalisées logiciel analyse d’images. Notre analyse a été réalisée à l’aide de nos propres logiciels écrits à l’aide d’une analyse scientifique paquet13. Le logiciel devrait créer un masque à l’aide de l’image de contraste de phase et extraire des valeurs de fluorescence des zones masquées à l’image de fluorescence. Valeurs de fluorescence sont en moyenne sur au moins 100 cellules, ayant pour résultat un index de mise à mort d’hôte numérique.

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			<td height="21" style="height:21px;width:220px;">Reagents</td>
			<td style="width:108px;"></td>
			<td style="width:91px;"></td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Bacto agar, dehydrated</td>
			<td style="width:108px;">BD Difco</td>
			<td style="width:91px;">214010</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Antibiotic-Antimycotic (100X)</td>
			<td style="width:108px;">Life Technologies</td>
			<td style="width:91px;">15240062</td>
			<td style="width:297px;">Aliquot &#60; 1 mL and store at -20 &#176;C</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Calcein-acetoxymethyl ester (calcein-AM)</td>
			<td style="width:108px;">Life Technologies</td>
			<td style="width:91px;">C34852</td>
			<td style="width:297px;">Calcein Acetoxymethyl (AM)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Calcium chloride, anhydrous</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">C1016</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">D-Glucose</td>
			<td style="width:108px;">Fisher Chemical</td>
			<td style="width:91px;">D16500</td>
			<td style="width:297px;">Dextrose</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Dimethyl sulfoxide</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">D5879</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Folic acid</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">F8758</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">LB-Miller</td>
			<td style="width:108px;">BD Difco</td>
			<td style="width:91px;">244620</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Magnesium chloride</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">M8266</td>
			<td style="width:297px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Yeast extract</td>
			<td style="width:108px;">Oxoid</td>
			<td style="width:91px;">LP0021</td>
			<td style="width:297px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Special peptone</td>
			<td style="width:108px;">Oxoid</td>
			<td style="width:91px;">LP0072</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Potassium hyroxide</td>
			<td style="width:108px;">Fisher Chemical</td>
			<td style="width:91px;">P250</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Potassium phosphate monobasic&#160;</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">P0662</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Sodium phosphate dibasic heptahydrate</td>
			<td style="width:108px;">Fisher Chemical</td>
			<td style="width:91px;">S373</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Vitamin B12</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:91px;">V2876</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Strains</td>
			<td style="width:108px;"></td>
			<td style="width:91px;"></td>
			<td style="width:297px;"></td>
		</tr>
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			<td height="45" style="height:45px;width:220px;">Dictyostelium discoideum</td>
			<td style="width:108px;">Siryaporn lab</td>
			<td style="width:91px;">Strain AX318</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:220px;">Escherichia coli</td>
			<td style="width:108px;">Siryaporn lab</td>
			<td style="width:91px;">Strain B/r17</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:220px;">Pseudomonas aeruginosa</td>
			<td style="width:108px;">Siryaporn lab</td>
			<td style="width:91px;">PA14</td>
			<td style="width:297px;">PA14 strain19</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Pseudomonas aeruginosa &#916;lasR</td>
			<td style="width:108px;">Siryaporn lab</td>
			<td style="width:91px;">AFS20.1</td>
			<td style="width:297px;">PA14-derived strain20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Supplies</td>
			<td style="width:108px;"></td>
			<td style="width:91px;"></td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">0.22 &#181;m filter&#160;</td>
			<td style="width:108px;">Millipore</td>
			<td style="width:91px;">SCGPT01RE</td>
			<td style="width:297px;">For filter sterilization</td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:220px;">Conical tube, 15 mL</td>
			<td style="width:108px;">Corning</td>
			<td style="width:91px;">352097</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Glass storage bottles</td>
			<td style="width:108px;">Pyrex</td>
			<td style="width:91px;">13951L</td>
			<td style="width:297px;">250 mL, 500 mL, 1000 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Petri dish, 6 cm diameter</td>
			<td style="width:108px;">Corning</td>
			<td style="width:91px;">351007</td>
			<td style="width:297px;">60 x 15 mm polystyrene plates</td>
		</tr>
		<tr height="37">
			<td height="37" style="height:37px;width:220px;">Petri dish, 10 cm diameter</td>
			<td style="width:108px;">Fisher</td>
			<td style="width:91px;">FB0875712</td>
			<td style="width:297px;">100 x 15 mm polystyrene plates</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:220px;">Plastic containers with lid</td>
			<td style="width:108px;">Ziploc</td>
			<td style="width:91px;">2.57E+09</td>
			<td style="width:297px;">Square 3-cup containers</td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:220px;">Glass plates</td>
			<td style="width:108px;">Bio-Rad</td>
			<td style="width:91px;">1653308</td>
			<td style="width:297px;">For preparing agar pads. Other glass plates may be used with similar dimensions.</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:220px;">Wooden sticks</td>
			<td style="width:108px;">Fisher</td>
			<td style="width:91px;">23-400-102&#160;</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Equipment</td>
			<td style="width:108px;"></td>
			<td style="width:91px;"></td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Eclipse Ti-E microscope&#160;</td>
			<td style="width:108px;">Nikon</td>
			<td style="width:91px;">MEA53100</td>
			<td style="width:297px;">Microscope setup</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">10X Plan Fluor Ph1 objective&#160; 0.3 NA</td>
			<td style="width:108px;">Nikon</td>
			<td style="width:91px;">MRH20101</td>
			<td style="width:297px;">Microscope setup</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Fluorescence excitation source</td>
			<td style="width:108px;">Lumencor</td>
			<td style="width:91px;">Sola light engine</td>
			<td style="width:297px;">Microscope setup</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:220px;">Fluorescence filter set</td>
			<td style="width:108px;">Semrock</td>
			<td style="width:91px;">LED-DA/FI/TX-3X3M-A-000&#160;</td>
			<td style="width:297px;">Microscope setup</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Orca Flash 4.0 V2 Camera</td>
			<td style="width:108px;">Hamamatsu</td>
			<td style="width:91px;">77054098</td>
			<td style="width:297px;">Microscope setup</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">ImageJ</td>
			<td style="width:108px;">NIH</td>
			<td style="width:91px;">v. 1.49</td>
			<td style="width:297px;">Software for image analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">MATLAB</td>
			<td style="width:108px;">Mathworks</td>
			<td style="width:91px;">R2013</td>
			<td style="width:297px;">Software for image analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:220px;">Orbital shaker incubator</td>
			<td style="width:108px;">VWR</td>
			<td style="width:91px;">89032-092</td>
			<td style="width:297px;">For growth of bacteria at 37 &#176;C</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Platform shaker</td>
			<td style="width:108px;">Fisher</td>
			<td style="width:91px;">13-687-700</td>
			<td style="width:297px;">For growth of amoebae at 22 &#176;C</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Spectrophotometer</td>
			<td style="width:108px;">Biochrom</td>
			<td style="width:91px;">Ultrospec 10</td>
			<td style="width:297px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Undercounter refrigerated incubator</td>
			<td style="width:108px;">Fisher</td>
			<td style="width:91px;">97990E</td>
			<td style="width:297px;">For growth of amoebae at 22 &#176;C</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:220px;">Isotemp waterbath&#160;</td>
			<td style="width:108px;">Fisher</td>
			<td style="width:91px;">15-462-21Q</td>
			<td style="width:297px;">For cooling media to 55 &#176;C</td>
		</tr>
	</tbody>
</table>

a rapid image-based bacterial virulence assay using amoeba

Les dosages traditionnels de la virulence bactérienne impliquent une exposition prolongée des bactéries au cours de plusieurs heures pour les cellules de l’hôte. Pendant ce temps, bactéries peuvent subir des changements dans la physiologie en raison de l’exposition à l’environnement de croissance d’hôte et la présence de cellules hôtes. Nous avons mis au point un test permettant de mesurer rapidement l’état de la virulence des bactéries qui réduisent au minimum l’étendue à laquelle les bactéries se développent en présence de cellules de l’hôte. Les bactéries et les amibes sont mélangés et immobilisés sur un seul plan d’imagerie à l’aide d’un tampon d’agar. La procédure utilise imagerie de fluorescence monocellulaires avec calcéine-acétoxyméthyl ester (calcéine-AM) comme indicateur de la santé de cellule hôte. La fluorescence des cellules de l’hôte est analysée après 1 h d’exposition des cellules hôtes aux bactéries à l’aide de la microscopie à épifluorescence. Logiciel d’analyse image est utilisée pour calculer un index de mise à mort d’hôte. Cette méthode a été utilisée pour mesurer la virulence dans planctoniques et attaché à la surface Pseudomonas aeruginosa sous-populations durant le stade initial de la formation de biofilm et peuvent être adaptées à d’autres bactéries et autres stades de croissance de biofilm. Ce protocole fournit une méthode rapide et fiable de mesurer la virulence et évite beaucoup des complexités liées à la croissance et le maintien des lignées cellulaires de mammifères. Phénotypes de résistance mesurées ici à l’aide d’amibes ont également été validés à l’aide de macrophages de souris. En particulier, ce test a été utilisé pour établir cette virulence augmente de surface pièce jointe chez P. aeruginosa.

Nous avons grandi sauvage souche de P. aeruginosa PA1419 ou un ΔlasR souche20 dans le même contexte de PA14 en Pétri de 6 cm de diamètre et dosé la virulence des cellules planctoniques et attaché à la surface. Les cultures ont été inoculés de single-colonies à PS:DB cultures, du jour au lendemain en tubes de culture dans un fût de rouleau à 37 ° C à saturation, dilué au 1/100 en PS:DB, cultivés pendant 8 h ...

Watch this Scientific Journal Video about A Rapid Image-based Bacterial Virulence Assay Using Amoeba at JoVE.com

A Rapid Image-based Bacterial Virulence Assay Using Amoeba

Un dosage de la Virulence bactérienne rapide basé sur une Image à l’aide d’amibe

Nous présentons ici un protocole visant à mesurer la virulence de bactéries planctoniques ou attaché à la surface à l’aide de d. discoideum (amibes) en tant qu’hôte. Virulence est mesurée sur une période de 1 h et hôte tuant est quantifiée à l’aide de fluorescence microscopie et analyse d’images. Nous démontrons ce protocole à l’aide de la bactérie P. aeruginosa.

Traditional bacterial virulence assays involve prolonged exposure of bacteria over the course of several hours to host cells. During this time, bacteria ...

This method can help answer key questions in the bacterial pathogenesis field, such as when are host-killing virulence effectors expressed in bacterial cells, and what are the virulence states of surface-attached implantonic cells? The main advantage of this technique is that it is fast, quantitative and the host cells are relatively easy to handle. We first had the idea for this method when we noticed that surface-attached implantonic subpopulation of Pseudomonas have different host-killing phenotypes.To begin grow E.coli strain BR overnight as outlined in the text protocol. Then bring the E.coli culture to room temperature. Using a wooden stick, innoculate amoeba into 750 l of the culture.Immediately add 700 l of the amoeba E.coli mixture to a GYP plate. Tilt the plate to spread the culture evenly on the surface of the plate. Then place the plate in a box that maintains high humidity.Incubate the plate inside of the box at 22 C for four to five days. After the incubation period is over, use a sterile pipette tip to collect amoeba spores from half of the plate. Then pipette up and down to resuspend the amoeba on the pipette tip in 1 mL of PS medium.Transfer the inoculate mixture to a 250 mL flask with 25 mL of PS medium supplemented with antibiotic antimicotic solution. Grow the amoeba at 22 C in a rotating shaker at 100 rpm. After culturing Pseudomonas aeruginosa overnight, dilute the culture with PSB media in a 6 cm petri dish.Then shake the culture on a benchtop rotator set to 100 rpm at 37 C.First microwave 50 mL of 1%agar in DB buffer in a 250 mL flask. Add 15 L of calcium AM to the 15 mL of molten agar and mix gently. Pour the molten agar mixture into a 12 by 10 cm glass plate, and allow the agar to solidify for ten minutes at room temperature.Next use a metal ruler and a printed grid to cut the solidified agar pad into smaller 1.5 by 1.5 cm sections. Ensure the gel remains hydrated until it is ready for use. Next, to isolate the cells attached to the surface, remove the liquid medium from the petri dish.Then wash the dish with 1 mL of development buffer to remove the planktonic cells. To assay virulence of surface attached bacteria cells, add 10 L of amoeba cells from the previously obtained surface attached bacterial cells. To isolate the planktonic cells, transfer 10 L of the culture to a fresh petri dish.Next, assay the virulence of planktonic cells by mixing 10 L of amoeba cells with the previously obtained planktonic bacteria. Immediately place the small agar pad on top of the appropriate bacteria amoeba mixture on the petri dish surface. Then, remove excess liquid by gently pipetting any excess liquid, and allow the dish to dry for 20 minutes.Cover the dish with the lid and incubate it at room temperature for an additional 40 minutes. Finally, use a fluorescence microscope to acquire images for at least 100 amoeba cells. In this protocol, the virulence of planktonic and surface-attached Pseudomonas aeruginosa cells was assayed.Surface-attached wild type Pseudomonas aeruginosa killed amoeba indicated by a round amoeba cell shape and the presence of calcein fluorescence. Compared to planktonic cells surface-attached wild type Pseudomonas aeruginosa had a high host killing index. Planktonic cells were consumed by the amoeba indicated by the amorphous amoeba cell shapes and relatively little calcein fluorescence.While attempting this procedure, it is important to remember to use a fresh stock of calcein AM, and amoeba cells and keep a close track of the optical density of amoeba. Following this procedure, other methods like transcription profiling can be performed in order to answer additional questions like Which genes are activated in planktonic and surface-attached subpopulation? After watching this video you should have a good understanding of how to conduct the rapid image-based virulence assay.

a-rapid-image-based-bacterial-virulence-assay-using-amoeba

Research

JoVE Journal

Bioengineering

Characterizing Bacterial Volatiles using Secondary Electrospray Ionization Mass Spectrometry (SESI-MS)

Secondary electrospray ionization mass spectrometry (SESI-MS) is a method developed for the rapid detection of volatile compounds, without the need for sample pretreatment. The method was first described by Fenn and colleagues1 and has been applied to the detection of illicit drugs2 and explosives3-4, the characterization of skin volatiles5, and the analysis of breath6-7.
SESI ionization occurs by proton transfer reactions between the electrospray solution and the volatile analyte, and is therefore suitable for the analysis of hetero-organic molecules, just as in traditional electrospray ionization (ESI). However, unlike standard ESI, the proton transfer process of SESI occurs in the vapor phase rather than in solution (Fig. 1), and therefore SESI is best suited for detecting organic volatiles and aerosols.
We are expanding the use of SESI-MS to the detection of bacterial volatiles as a method for bacterial identification and characterization8. We have demonstrated that SESI-MS volatile fingerprinting, combined with a statistical analysis method, can be used to differentiate bacterial genera, species, and mixed cultures in a variety of growth media.8 Here we provide the steps for obtaining bacterial volatile fingerprints using SESI-MS, including the instrumental parameters that should be optimized to ensure robust bacterial identification and characterization.

Characterizing Bacterial Volatiles using Secondary Electrospray Ionization Mass Spectrometry SESI-MS

Secondary electrospray ionization mass spectrometry (SESI-MS) enables the detection of volatile organic compounds (VOCs) without the need for any sample pretreatment. This protocol provides instructions for the rapid (within minutes) characterization of bacterial VOCs using SESI-MS.

Caractériser Volatiles bactérienne secondaire à l&#39;aide d&#39;ionisation électrospray spectrométrie de masse (SESI-MS)

Secondary electrospray ionization mass spectrometry (SESI-MS) is a method developed for the rapid detection of volatile compounds, without the need for ...

Recherche

Bio-ingénierie

Bacterial Detection &amp; Identification Using Electrochemical Sensors

Electrochemical sensors are widely used for rapid and accurate measurement of blood glucose and can be adapted for detection of a wide variety of analytes. Electrochemical sensors operate by transducing a biological recognition event into a useful electrical signal. Signal transduction occurs by coupling the activity of a redox enzyme to an amperometric electrode. Sensor specificity is either an inherent characteristic of the enzyme, glucose oxidase in the case of a glucose sensor, or a product of linkage between the enzyme and an antibody or probe.
Here, we describe an electrochemical sensor assay method to directly detect and identify bacteria. In every case, the probes described here are DNA oligonucleotides. This method is based on sandwich hybridization of capture and detector probes with target ribosomal RNA (rRNA). The capture probe is anchored to the sensor surface, while the detector probe is linked to horseradish peroxidase (HRP). When a substrate such as 3,3',5,5'-tetramethylbenzidine (TMB) is added to an electrode with capture-target-detector complexes bound to its surface, the substrate is oxidized by HRP and reduced by the working electrode. This redox cycle results in shuttling of electrons by the substrate from the electrode to HRP, producing current flow in the electrode.

We describe an electrochemical sensor assay method for rapid bacterial detection and identification. The assay involves a sensor array functionalized with DNA oligonucleotide capture probes for ribosomal RNA (rRNA) species-specific sequences. Sandwich hybridization of target rRNA with the capture probe and a horseradish peroxidase-linked DNA oligonucleotide detector probe produces a measurable amperometric current.

Bacterial Detection &amp; identification au moyen de capteurs électrochimiques

Electrochemical  sensors are widely used for rapid and accurate measurement of blood glucose and  can be adapted for detection of a wide variety of ...

Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding

Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using traditional liquid injection molding processes can be an expensive process due to tooling and equipment costs. As a result, it has traditionally been impractical to use liquid injection molding for low-cost, rapid prototyping applications. We have devised a method for rapid and low-cost production of liquid elastomer injection molded devices that utilizes fused deposition modeling 3D printers for mold design and a modified desiccator as an injection system. Low costs and rapid turnaround time in this technique lower the barrier to iteratively designing and prototyping complex elastomer devices. Furthermore, CAD models developed in this process can be later adapted for metal mold tooling design, enabling an easy transition to a traditional injection molding process. We have used this technique to manufacture intravaginal probes involving complex geometries, as well as overmolding over metal parts, using tools commonly available within an academic research laboratory. However, this technique can be easily adapted to create liquid injection molded devices for many other applications.

We have devised a method for low-cost and rapid prototyping of liquid elastomer rubber injection molded devices by using fused deposition modeling 3D printers for mold design and a modified desiccator as a liquid injection system.

Prototypage rapide et à faible coût des dispositifs médicaux utilisant 3D Imprimé moules pour injection de liquide

Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using ...

Measuring TCR-pMHC Binding In Situ using a FRET-based Microscopy Assay

T-cells are remarkably specific and effective when recognizing antigens in the form of peptides embedded in MHC molecules (pMHC) on the surface of Antigen Presenting Cells (APCs). This is despite T-cell antigen receptors (TCRs) exerting usually a moderate affinity (&#181;M range) to antigen when binding is measured in vitro1. In view of the molecular and cellular parameters contributing to T-cell antigen sensitivity, a microscopy-based methodology has been developed as a means to monitor TCR-pMHC binding in situ, as it occurs within the synapse of a live T-cell and an artificial and functionalized glass-supported planar lipid bilayer (SLB), which mimics the cell membrane of an Antigen presenting Cell (APC) 2. Measurements are based on F&#246;rster Resonance Energy Transfer (FRET) between a blue- and red-shifted fluorescent dye attached to the TCR and the pMHC. Because the efficiency of FRET is inversely proportional to the sixth power of the inter-dye distance, one can employ FRET signals to visualize synaptic TCR-pMHC binding. The sensitive of the microscopy approach supports detection of single molecule FRET events. This allows to determine the affinity and off-rate of synaptic TCR-pMHC interactions and in turn to interpolate the on-rate of binding. Analogous assays could be applied to measure other receptor-ligand interactions in their native environment.

Measuring TCR-pMHC Binding In Situ using a FRET-based Microscopy Assay

This manuscript describes how to conduct (single molecule) F&#246;rster Resonance Energy Transfer (FRET)- based assays to measure the binding dynamics between T-cell antigen receptor (TCR) and antigenic peptide-loaded MHC molecules as they occur within the immunological synapse of a T-cell in contact with a functionalized planar supported lipid bilayer.

Mesure de TCR-pMHC Reliure<em&gt; In Situ</em&gt; L&#39;aide d&#39;un essai basé sur la microscopie FRET-

T-cells are remarkably specific and effective when recognizing antigens in the form of peptides embedded in MHC molecules (pMHC) on the surface of Antigen ...

A Rapid and Chemical-free Hemoglobin Assay with Photothermal Angular Light Scattering

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis of the intrinsic photothermal response of hemoglobin molecules, the sensor enables high-sensitivity, chemical-free measurement of [Hb]. [Hb] detection capability with a limit of 0.12 g/dl over the range of 0.35 - 17.9 g/dl has been demonstrated previously. The method can be readily implemented using inexpensive consumer electronic devices such as a laser pointer and a webcam. The use of a micro-capillary tube as a blood container also enables the hemoglobin assay with a nanoliter-scale blood volume and a low operating cost. Here, detailed instructions for the PT-AS optical setup and signal processing procedures are presented. Experimental protocols and representative results for blood samples in anemic conditions ([Hb] = 5.3, 7.5, and 9.9 g/dl) are also provided, and the measurements are compared with those from a hematology analyzer. Its simplicity in implementation and operation should enable its wide adoption in clinical laboratories and resource-limited settings.

A photo-thermal angular light scattering (PT-AS) sensor enables the rapid and chemical-free hemoglobin assay of nanoliter-scale blood samples. Here, details of the PT-AS setup and a measurement protocol for the hemoglobin concentration in blood are provided. Representative results for anemic blood samples are also presented.

A Hémoglobine Assay rapide et sans produits chimiques avec Photothermique angulaire Light Scattering

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis ...

Rapid Mix Preparation of Bioinspired Nanoscale Hydroxyapatite for Biomedical Applications

Hydroxyapatite (HA) has been widely used as a medical ceramic due to its good biocompatibility and osteoconductivity. Recently there has been interest regarding the use of bioinspired nanoscale hydroxyapatite (nHA). However, biological apatite is known to be calcium-deficient and carbonate-substituted with a nanoscale platelet-like morphology. Bioinspired nHA has the potential to stimulate optimal bone tissue regeneration due to its similarity to bone and tooth enamel mineral. Many of the methods currently used to fabricate nHA both in the laboratory and commercially, involve lengthy processes and complex equipment. Therefore, the aim of this study was to develop a rapid and reliable method to prepare high quality bioinspired nHA. The rapid mixing method developed was based upon an acid-base reaction involving calcium hydroxide and phosphoric acid. Briefly, a phosphoric acid solution was poured into a calcium hydroxide solution followed by stirring, washing and drying stages. Part of the batch was sintered at 1,000 &#176;C for 2 h in order to investigate the products&#39; high temperature stability. X-ray diffraction analysis showed the successful formation of HA, which showed thermal decomposition to &#946;-tricalcium phosphate after high temperature processing, which is typical for calcium-deficient HA. Fourier transform infrared spectroscopy showed the presence of carbonate groups in the precipitated product. The nHA particles had a low aspect ratio with approximate dimensions of 50 x 30 nm, close to the dimensions of biological apatite. The material was also calcium deficient with a Ca:P molar ratio of 1.63, which like biological apatite is lower than the stoichiometric HA ratio of 1.67. This new method is therefore a reliable and far more convenient process for the manufacture of bioinspired nHA, overcoming the need for lengthy titrations and complex equipment. The resulting bioinspired HA product is suitable for use in a wide variety of medical and consumer health applications.

This paper describes a novel method for the rapid manufacture of high quality bioinspired nanoscale hydroxyapatite. This biomaterial is of great significance in the manufacture of a wide range of innovative medical devices for clinical applications in orthopedics, craniofacial surgery and dentistry.

Mix rapide Préparation de bioinspirée Nanoscale hydroxyapatite pour applications biomédicales

Hydroxyapatite (HA) has been widely used as a medical ceramic due to its good biocompatibility and osteoconductivity. Recently there has been interest ...

An Automated Method to Perform The In Vitro Micronucleus Assay using Multispectral Imaging Flow Cytometry

The in vitro micronucleus (MN) assay is often used to evaluate cytotoxicity and genotoxicity but scoring the assay via manual microscopy is laborious and introduces uncertainty in results due to variability between scorers. To remedy this, automated slide-scanning microscopy as well as conventional flow cytometry methods have been introduced in an attempt to remove scorer bias and improve throughput. However, these methods have their own inherent limitations such as inability to visualize the cytoplasm of the cell and the lack of visual MN verification or image data storage with flow cytometry. Multispectral Imaging Flow Cytometry (MIFC) has the potential to overcome these limitations. MIFC combines the high resolution fluorescent imagery of microscopy with the statistical robustness and speed of conventional flow cytometry. In addition, all collected imagery can be stored in dose-specific files. This paper describes the protocol developed to perform a fully automated version of the MN assay on MIFC. Human lymphoblastoid TK6 cells were enlarged using a hypotonic solution (75 mM KCl), fixed with 4% formalin and the nuclear content was stained with Hoechst 33342. All samples were run in suspension on the MIFC, permitting acquisition of high resolution images of all key events required for the assay (e.g. binucleated cells with and without MN as well as mononucleated and polynucleated cells). Images were automatically identified, categorized and enumerated in the MIFC data analysis software, allowing for automated scoring of both cytotoxicity and genotoxicity. Results demonstrate that using MIFC to perform the in vitro MN assay allows statistically significant increases in MN frequency to be detected at several different levels of cytotoxicity when compared to solvent controls following exposure of TK6 cells to Mitomycin C and Colchicine, and that no significant increases in MN frequency are observed following exposure to Mannitol.

The in vitro micronucleus assay is a well-established method for evaluating genotoxicity and cytotoxicity but scoring the assay using manual microscopy is laborious and suffers from subjectivity and inter-scorer variability. This paper describes the protocol developed to perform a fully automated version of the assay using multispectral imaging flow cytometry.

Une méthode automatisée pour effectuer l'essai micronutrique in vitro à l'aide de la cytométrie du flux d'imagerie multispectrale

The in vitro micronucleus (MN) assay is often used to evaluate cytotoxicity and genotoxicity but scoring the assay via manual microscopy is laborious and ...

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.

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.

Identification à haut débit de la résistance aux seringues Pseudomonas pv. Tomate dans la tomate à l’aide de semis Flood Assay

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

Rapid Assembly of Multi-Gene Constructs using Modular Golden Gate Cloning

The Golden Gate cloning method enables the rapid assembly of multiple genes in any user-defined arrangement. It utilizes type IIS restriction enzymes that cut outside of their recognition sites and create a short overhang. This modular cloning (MoClo) system uses a hierarchical workflow in which different DNA parts, such as promoters, coding sequences (CDS), and terminators, are first cloned into an entry vector. Multiple entry vectors then assemble into transcription units. Several transcription units then connect into a multi-gene plasmid. The Golden Gate cloning strategy is of tremendous advantage because it allows scar-less, directional, and modular assembly in a one-pot reaction. The hierarchical workflow typically enables the facile cloning of a large variety of multi-gene constructs with no need for sequencing beyond entry vectors. The use of fluorescent protein dropouts enables easy visual screening. This work provides a detailed, step-by-step protocol for assembling multi-gene plasmids using the yeast modular cloning (MoClo) kit. We show optimal and suboptimal results of multi-gene plasmid assembly and provide a guide for screening for colonies. This cloning strategy is highly applicable for yeast metabolic engineering and other situations in which multi-gene plasmid cloning is required.

The goal of this protocol is to provide a detailed, step-by-step guide for assembling multi-gene constructs using the modular cloning system based on Golden Gate cloning. It also gives recommendations on critical steps to ensure optimal assembly based on our experiences.

Assemblage rapide de constructions multigéniques à l’aide du clonage modulaire golden gate

The Golden Gate cloning method enables the rapid assembly of multiple genes in any user-defined arrangement. It utilizes type IIS restriction enzymes that ...

3D Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell cultures. Microcarrier culture technology has become one of the main techniques in cytological research and is commonly used in the field of large-scale cell expansion. Microcarriers have also been shown to play an increasingly important role in in vitro tissue engineering construction and clinical drug screening. Current methods for preparing microcarriers include microfluidic chips and inkjet printing, which often rely on complex flow channel design, an incompatible two-phase interface, and a fixed nozzle shape. These methods face the challenges of complex nozzle processing, inconvenient nozzle changes, and excessive extrusion forces when applied to multiple bioink. In this study, a 3D printing technique, called alternating viscous-inertial force jetting, was applied to enable the construction of hydrogel microcarriers with a diameter of 100-300 &#181;m. Cells were subsequently seeded on microcarriers to form tissue engineering modules. Compared to existing methods, this method offers a free nozzle tip diameter, flexible nozzle switching, free control of printing parameters, and mild printing conditions for a wide range of bioactive materials.

3D Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Presented here is a mild 3D printing technique driven by alternating viscous-inertial forces to enable the construction of hydrogel microcarriers. Homemade nozzles offer flexibility, allowing easy replacement for different materials and diameters. Cell binding microcarriers with a diameter of 50-500 &#181;m can be obtained and collected for further culturing.

Impression 3D de microporteurs d’hydrogel in vitro par jet de force visqueuse-inertielle alternée

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell ...