Name: time-lapse imaging of bacterial swarms and the collective stress response
Uploaded: 2020-05-23T13:30:00
Description: Watch this Scientific Journal Video about Time-lapse Imaging of Bacterial Swarms and the Collective Stress Response at JoVE.com

J.-L.B., A.S., and N.M.H-K. wrote and revised the manuscript. All authors designed the experiments. J.-L.B. performed the experiments and analysis. This work was supported by NIH award K22AI112816 and R21AI139968 grant to A.S. and by the University of California. N.M.H-K. was supported by Lundbeck Fellowships R220-2016-860 and R251-2017-1070. The funders had no role in the decision to submit the work for publication. We have no competing interests to declare.

1. Preparing Swarming Agar Plates for P. aeruginosa Swarming Time-lapse Imaging
<ol>
	<li>Prepare 1 L of 5x M8 minimum media in a glass bottle by adding 64 g of Na2HPO4&#8226;7H2O, 15 g of KH2PO4, and 2.5 g of NaCl in 500 mL double-distilled water (ddH2O). Adjust the final volume to 1 L with additional ddH2O. Autoclave to sterilize and store liquid media at room temperature.</li>
	<li>Prepare 100 mL of 1 M MgSO4 (magnesium ...

<ol>
	<li>Butler, M. T., Wang, Q., Harshey, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+density+and+mobility+protect+swarming+bacteria+against+antibiotics.">Cell density and mobility protect swarming bacteria against antibiotics.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (8), 3776-3781 (2010).</li><li>Lai, S., Tremblay, J., D&#233;ziel, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swarming+motility:+a+multicellular+behaviour+conferring+antimicrobial+resistance.">Swarming motility: a multicellular behaviour conferring antimicrobial resistance.</a> Environmental Microbiology. 11 (1), 126-136 (2009).</li><li>Overhage, J., Bains, M., Brazas, M. D., Hancock, R. E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swarming+of+Pseudomonas+aeruginosa+is+a+complex+adaptation+leading+to+increased+production+of+virulence+factors+and+antibiotic+resistance.">Swarming of Pseudomonas aeruginosa is a complex adaptation leading to increased production of virulence factors and antibiotic resistance.</a> Journal of Bacteriology. 190 (8), 2671-2679 (2008).</li><li>Yeung, A. T. Y., 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=Swarming+of+Pseudomonas+aeruginosa+is+controlled+by+a+broad+spectrum+of+transcriptional+regulators,+including+MetR.">Swarming of Pseudomonas aeruginosa is controlled by a broad spectrum of transcriptional regulators, including MetR.</a> Journal of Bacteriology. 191 (18), 5592-5602 (2009).</li><li>Girod, S., Zahm, J. 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H., Zinjarde, S. S., Venugopalan, V. P., McLean, R. J. C., Weber, M. M., Rahman, P. K. S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quorum+sensing:+implications+on+rhamnolipid+biosurfactant+production.">Quorum sensing: implications on rhamnolipid biosurfactant production.</a> Biotechnology &amp; Genetic Engineering Reviews. 27, 159-184 (2010).</li><li>K&#246;hler, T., Curty, L. K., Barja, F., van Delden, C., Pech&#232;re, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swarming+of+Pseudomonas+aeruginosa+is+dependent+on+cell-to-cell+signaling+and+requires+flagella+and+pili.">Swarming of Pseudomonas aeruginosa is dependent on cell-to-cell signaling and requires flagella and pili.</a> Journal of Bacteriology. 182 (21), 5990-5996 (2000).</li><li>Pollitt, E. J. G., Crusz, S. A., Diggle, S. 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P., L&#233;pine, F., D&#233;ziel, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-produced+extracellular+stimuli+modulate+the+Pseudomonas+aeruginosa+swarming+motility+behaviour.">Self-produced extracellular stimuli modulate the Pseudomonas aeruginosa swarming motility behaviour.</a> Environmental Microbiology. 9 (10), 2622-2630 (2007).</li><li>Morales-Soto, N., 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=Spatially+dependent+alkyl+quinolone+signaling+responses+to+antibiotics+in+Pseudomonas+aeruginosa+swarms.">Spatially dependent alkyl quinolone signaling responses to antibiotics in Pseudomonas aeruginosa swarms.</a> The Journal of Biological Chemistry. 293 (24), 9544-9552 (2018).</li><li>Bru, J. -. L., 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=PQS+produced+by+the+Pseudomonas+aeruginosa+stress+response+repels+swarms+away+from+bacteriophage+and+antibiotics.">PQS produced by the Pseudomonas aeruginosa stress response repels swarms away from bacteriophage and antibiotics.</a> Journal of Bacteriology. , (2019).</li><li>van Kessel, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PQS+signaling+for+more+than+a+quorum:+the+collective+stress+response+protects+healthy+Pseudomonas+aeruginosa+populations.">PQS signaling for more than a quorum: the collective stress response protects healthy Pseudomonas aeruginosa populations.</a> Journal of Bacteriology. , (2019).</li><li>Zegans, M. E., 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=Interaction+between+bacteriophage+DMS3+and+host+CRISPR+region+inhibits+group+behaviors+of+Pseudomonas+aeruginosa.">Interaction between bacteriophage DMS3 and host CRISPR region inhibits group behaviors of Pseudomonas aeruginosa.</a> Journal of Bacteriology. 191 (1), 210-219 (2009).</li><li>Kamatkar, N. G., Shrout, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+hardness+impairment+of+quorum+sensing+and+swarming+for+Pseudomonas+aeruginosa.">Surface hardness impairment of quorum sensing and swarming for Pseudomonas aeruginosa.</a> PloS One. 6 (6), 20888 (2011).</li><li>Mattingly, A. E., Kamatkar, N. G., Morales-Soto, N., Borlee, B. R., Shrout, J. 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This protocol focuses on minimizing the variability in swarming agar plates and providing a simple and low-cost method to acquire time-lapse images of P. aeruginosa swarming and responding to stress. This procedure can be extended to image other bacterial systems by adapting the media composition and growth conditions. For P. aeruginosa, although M9 or FAB minimal medium can be used to induce swarming16,21, the protocol presented here uses M8 me...

Swarming is a collective form of coordinated bacterial motility that increases antibiotic resistance and production of virulence factors in the host1,2,3. This multicellular behavior occurs on semi-solid surfaces that resemble those of mucous layers covering epithelial membranes in the lungs4,5. Biosurfactants are commonly produced by swarming populations to overcome the surface tension on surfaces and the production of these is regulated by complex cell-cell signaling systems, also known as quorum sensing6,7,8. Many species of bacteria are capable of swarming, including Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli9,10,11,12. The swarming patterns created by bacteria are diverse and are affected by the physical and chemical properties of the surface layer including nutrient composition, porosity, and moisture13,14. In addition to surface properties, growth temperature and ambient humidity affect several aspects of swarming dynamics, including swarming rate and patterns12,13,14,15. The growth variables that affect swarming create challenges that impact experimental reproducibility and the ability to interpret results. Here, we describe a simple standardized method to monitor the dynamics of bacterial swarms through time-lapse imaging. The method describes how to control critical growth conditions that significantly affect the progression of swarming. Compared to traditional methods of swarm analysis, this time-lapse imaging method enables tracking the motility of multiple swarms concurrently during extended periods of time and with high resolution. These aspects improve the depth of data that can be gained from monitoring swarms and facilitate the identification of factors that affect swarming.
Swarming in P. aeruginosa is facilitated through the production and release of rhamnolipids and 3-(3-hydroxyalkanoyloxy)alkanoic acids into the surrounding area6,16. The introduction of stress from sub-lethal concentrations of antibiotics or infection by phage virus impacts the organization of swarms. In particular, these stresses induce P. aeruginosa to release the quorum sensing molecule 2-heptyl-3-hydroxy-4-quinolone, also known as the Pseudomonas quinolone signal (PQS)17,18. In swarm assays that contain two populations of swarms, PQS produced by the stress-induced population repels untreated swarms from entering the area containing the stress (Figure 1). This collective stress response constitutes a danger communication signaling system that warns P. aeruginosa about nearby threats18,19. The effects of stress on P. aeruginosa, the activation of the collective stress response, and the repulsion of swarms can be visualized using the time-lapse imaging method described here. The protocol described here explains how to: (1) prepare agar plates for swarming, (2) culture P. aeruginosa for two types of assays (traditional swarming assays or collective stress response assays) (Figure 1), (3) acquire time-lapse images, and (4) use ImageJ to compile and analyze the images.
Briefly, P. aeruginosa from an overnight culture is spotted in the middle of a swarming agar plate while P. aeruginosa that are infected with phage or treated with antibiotics are spotted at the satellite positions. The progression of P. aeruginosa swarming is monitored on a consumer document flatbed scanner that is placed in a humidity-regulated 37 &#176;C incubator. The scanner is controlled by a software that automatically scans the plates at regular intervals over the swarm growth period, typically 16&#8211;20 h. This method yields concurrent time-lapse videos of up to six 10 cm swarming plates. The images are compiled into movies and the repulsion of swarms by stress-induced populations is quantified by using freely available ImageJ software. Special consideration is given to ensure consistency and reproducibility between different swarming experiments.

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			<td height="21" style="height:21px;width:228px;">Reagents</td>
			<td style="width:157px;"></td>
			<td style="width:120px;"></td>
			<td style="width:339px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Bacto agar, dehydrated</td>
			<td style="width:157px;">BD Difco</td>
			<td style="width:120px;">214010</td>
			<td>For LB-agar plate and swarming agar plate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Casamino acids</td>
			<td style="width:157px;">BD Difco</td>
			<td style="width:120px;">223050</td>
			<td>For swarming media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">D-Glucose</td>
			<td style="width:157px;">Fisher Chemical</td>
			<td style="width:120px;">D16500</td>
			<td>Dextrose. For swarming media</td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:228px;">Fosfomycin disodium salt</td>
			<td style="width:157px;">Tokyo Chemical Industry</td>
			<td style="width:120px;">F0889</td>
			<td>Stock concentration: 200 mg / mL. Dissolved in ddH2O</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:228px;">Gentamycin sulfate</td>
			<td style="width:157px;">Sigma-Aldrich</td>
			<td style="width:120px;">G1914</td>
			<td>Stock concentration: 3 mg / mL. Dissolved in ddH2O</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:228px;">Kanamycin sulfate</td>
			<td style="width:157px;">Sigma-Aldrich</td>
			<td style="width:120px;">60615</td>
			<td>Stock concentration: 100 mg / mL. Dissolved in ddH2O</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">LB-Miller</td>
			<td style="width:157px;">BD Difco</td>
			<td style="width:120px;">244620</td>
			<td>For LB broth and LB-agar plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Magnesium sulfate heptahydrate</td>
			<td style="width:157px;">Sigma-Aldrich</td>
			<td style="width:120px;">230391</td>
			<td>For swarming media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Potassium phosphate monobasic</td>
			<td style="width:157px;">Sigma-Aldrich</td>
			<td style="width:120px;">P0662</td>
			<td>For 5X M8 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Sodium chloride</td>
			<td style="width:157px;">Sigma-Aldrich</td>
			<td style="width:120px;">S9888</td>
			<td>For 5X M8 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Sodium phosphate dibasic heptahydrate</td>
			<td style="width:157px;">Fisher Chemical</td>
			<td style="width:120px;">S373</td>
			<td>For 5X M8 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Strains</td>
			<td style="width:157px;"></td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
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			<td height="21" style="height:21px;width:228px;">Pseudomonas aeruginosa</td>
			<td style="width:157px;">Siryaporn lab</td>
			<td style="width:120px;">AFS27E.118</td>
			<td>PA14 strain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">DMS3vir</td>
			<td style="width:157px;">O&#39;Toole lab</td>
			<td style="width:120px;">DMS3vir20</td>
			<td>Bacteriophage</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Supplies</td>
			<td style="width:157px;"></td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Aluminium oxide sandpaper</td>
			<td style="width:157px;">3M</td>
			<td style="width:120px;">150 Fine</td>
			<td>For black lids</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Black fabric</td>
			<td style="width:157px;">Joann</td>
			<td style="width:120px;">PRD7089</td>
			<td>Black fabric</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Black spray paint</td>
			<td style="width:157px;">Krylon</td>
			<td style="width:120px;">5592 Matte Black</td>
			<td>For black lids</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Erlenmeyer flask</td>
			<td style="width:157px;">Kimax</td>
			<td style="width:120px;">26500</td>
			<td>250 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Glass storage bottles</td>
			<td style="width:157px;">Pyrex</td>
			<td style="width:120px;">13951L</td>
			<td>250 mL, 500 mL, 1000 mL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">8 inches zip ties</td>
			<td style="width:157px;">Gardner Bender</td>
			<td style="width:120px;">E173770</td>
			<td>For attaching black matte fabric</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Petri dishes (100 mm x 15 mm)</td>
			<td style="width:157px;">Fisher</td>
			<td style="width:120px;">FB0875712</td>
			<td>100 x 15 mm polystyrene plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Wooden sticks</td>
			<td style="width:157px;">Fisher</td>
			<td style="width:120px;">23-400-102</td>
			<td>For streaking and inoculating bacteria</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Equipment</td>
			<td style="width:157px;"></td>
			<td style="width:120px;"></td>
			<td></td>
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			<td height="21" style="height:21px;width:228px;">Autoclave</td>
			<td style="width:157px;">Market Forge Industries</td>
			<td style="width:120px;">STM-E</td>
			<td>For sterilizing reagents</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">25 mL pipette</td>
			<td style="width:157px;">USA Scientific, Inc.</td>
			<td style="width:120px;">1072-5410</td>
			<td>To pipet 20 mL for swarming agar plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Dehumidifier</td>
			<td style="width:157px;">Frigidaire</td>
			<td style="width:120px;">FAD704DWD 70-pint</td>
			<td>For maintaing room relative humidity at about 45%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">ImageJ</td>
			<td style="width:157px;">NIH</td>
			<td style="width:120px;">v1.52a</td>
			<td>Software for image analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Incubator</td>
			<td style="width:157px;">VWR</td>
			<td style="width:120px;">89032-092</td>
			<td>For growth of bacteria at 37 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Isotemp waterbath</td>
			<td style="width:157px;">Fisher</td>
			<td style="width:120px;">15-462-21Q</td>
			<td>For cooling media to 55 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Laminar flow hood</td>
			<td style="width:157px;">The Baker Company</td>
			<td style="width:120px;">SG603A</td>
			<td>For drying plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">P-20 pipet</td>
			<td style="width:157px;">Gilson</td>
			<td style="width:120px;">F123601</td>
			<td>Spotting on swarming agar plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Pipette Controller</td>
			<td style="width:157px;">BrandTech</td>
			<td style="width:120px;">accu-jet</td>
			<td>To pipet 20 mL for swarming agar plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Roller Drum</td>
			<td style="width:157px;">New Brunswick</td>
			<td style="width:120px;">TC-7</td>
			<td>For growth of bacteria at 100 rpm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Scanner</td>
			<td style="width:157px;">Epson</td>
			<td style="width:120px;">Epson Perfection V370 Photo</td>
			<td>Scanner for imaging plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:228px;">Scanner automation software</td>
			<td style="width:157px;">RoboTask Lite</td>
			<td style="width:120px;">v7.0.1.932</td>
			<td>For 30-min internals imaging</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:228px;">Scanner image acquisition software</td>
			<td style="width:157px;">Epson</td>
			<td style="width:120px;">v9.9.2.5US</td>
			<td>Software for imaging plates</td>
		</tr>
	</tbody>
</table>

time-lapse imaging of bacterial swarms and the collective stress response

Swarming is a form of surface motility observed in many bacterial species including Pseudomonas aeruginosa and Escherichia coli. Here, dense populations of bacteria move over large distances in characteristic tendril-shaped communities over the course of hours. Swarming is sensitive to several factors including medium moisture, humidity, and nutrient content. In addition, the collective stress response, which is observed in P. aeruginosa that are stressed by antibiotics or bacteriophage (phage), repels swarms from approaching the area containing the stress. The methods described here address how to control the critical factors that affect swarming. We introduce a simple method to monitor swarming dynamics and the collective stress response with high temporal resolution using a flatbed document scanner, and describe how to compile and perform a quantitative analysis of swarms. This simple and cost-effective method provides precise and well-controlled quantification of swarming and may be extended to other types of plate-based growth assays and bacterial species.

The steps to grow P. aeruginosa, stress the cells, and image the swarming agar plates are represented in Figure 1. We inoculated a single colony of wild-type P. aeruginosa UCBPP-PA14 strain from an LB-agar plate in 2 mL of LB broth overnight at 37 &#176;C and spotted 5 &#181;L in the center of the swarming agar plate. Time-lapse imaging of this plate reveals initial growth in the form of a colony at the center and then spreading of tendrils radially from the colony (Video 1</str...

Watch this Scientific Journal Video about Time-lapse Imaging of Bacterial Swarms and the Collective Stress Response at JoVE.com

Time-lapse Imaging of Bacterial Swarms and the Collective Stress Response

We detail a simple method to produce high-resolution time-lapse movies of Pseudomonas aeruginosa swarms that respond to bacteriophage (phage) and antibiotic stress using a flatbed document scanner. This procedure is a fast and simple method for monitoring swarming dynamics and may be adapted to study the motility and growth of other bacterial species.

Swarming is a form of surface motility observed in many bacterial species including Pseudomonas aeruginosa and Escherichia coli. Here, dense populations ...

This protocol can be used to produce time-lapse movies of Pseudomonas aeruginosa swarming and to capture the repulsion of swarm by bacteriophage or antibiotics. The time-lapse movies capture the detailed dynamics of the swarming response to antibiotics and bacteriophage and the technique only requires a dehumidifier, computer, incubator, and document scanner. To prepare swarming agar plates for P.aeruginosa swarming time-lapse imaging, use a 25 milliliter pipette to add 20 milliliters of swarming agar solution to each experimental 10 centimeter diameter Petri dish.Place the plates in a single stack with lids for one hour at room temperature. Turn on a dehumidifier to decrease the relative humidity of the room to 40-50%When the agar has solidified, dry the swarming agar plates for an additional 30 minutes in a laminar flow hood with the lids off and face up at 300 cubic feet per minute with a 40-50%relative humidity at room temperature. Then store the dried swarming agar plates at four degrees Celsius for up to 24 hours.For swarming agar plating, hold a P20 pipette tip loaded with five microliters from an overnight P.aeruginosa culture at a 10-45 degree angle 2-1/2 centimeters above the center of one swarming plate and depress the plunger to the first stop touching the agar with only the liquid drop. Use a template to position the spot consistently across the different swarming agar plates. To plate a phage infection, first mix 30 microliters of overnight cultured P.aeruginosa with six microliters of one times 10 to the 12 plaque-forming units per milliliter of phage DMS3 vir and immediately add six microliters of the P.aeruginosa phage mixture at six equidistant satellite positions on a 2.8 centimeter radius concentric circle as demonstrated.Use a template to position the spot consistently across different swarming agar plates. To plate antibiotic treatments, mix 30 microliters of overnight cultured P.aeruginosa with the appropriate concentration and volume of the antibiotic of interest and immediately add six microliters of the antibiotic-treated bacteria at six equidistant satellite positions on a 2.8 centimeter radius concentric circle about the center of the dish. Use a template to position the spot consistently across the different swarming agar plates.When all of the cultures have been plated, replace the clear Petri dish lids with custom-made black lids. Carefully place the swarming agar plates on a scanner in an incubator set at 37 degrees Celsius with a 10 liter water bath to maintain the humidity at 75%After placing the plates into the scanner, open file and save settings to set the saving path for the images and click scan and OK at 30-minute intervals. To automate the image acquisition, use the scripting software.Select both idle scanning and single scan and right-click on idle scanning, then left-click on enabled. At the end of the incubation, import all of the scanned images into ImageJ. In the sequence options window, number of images will indicate the number of images selected.Keep starting image at one to start from the first picture in the folder and the scale images at 100%to conserve the original size of the images. Click covert to RGB to keep the images in color. Leave use virtual stack unchecked and click OK to load the images.Click file, save as and AVI to merge the images into an AVI file. Adjust the compression to JPEG and the frame rate to five frames per second. Then save the AVI time-lapse in the appropriate storage folder.Time-lapse imaging of a single colony of wild-type P.aeruginosa from an LB agar plate in LB broth overnight at 37 degrees Celsius and spotted into the center of a swarming agar plate reveals an initial growth in the form of a colony at the center of the plate that spreads in tendrils radially from the colony. Swarms move from the center of the swarming agar plates to the periphery and are repelled by a stress signal emitted by the bacteria that were infected with phages or treated with Gentamycin. Phages or Gentamycin spotted alone at the satellite positions do not cause swarming populations to avoid these areas.Use a 25 milliliter pipette to ensure that the swarming agar plates contain exactly 20 milliliters. It is also important to adjust the plate drying time according to the laboratory environment. Our technique enables us to visualize the overall swarming patterns of Pseudomonas aeruginosa populations.The next objective is to monitor individual cell motility using Brightfield microscopy.

time-lapse-imaging-bacterial-swarms-collective-stress

Research

JoVE Journal

Biology

Monitoring Actin Disassembly with Time-lapse Microscopy

Two-photon axotomy and time-lapse confocal imaging in live zebrafish embryos

Zebrafish have long been utilized to study the cellular and molecular mechanisms of development by time-lapse imaging of the living transparent embryo. Here we describe a method to mount zebrafish embryos for long-term imaging and demonstrate how to automate the capture of time-lapse images using a confocal microscope. We also describe a method to create controlled, precise damage to individual branches of peripheral sensory axons in zebrafish using the focused power of a femtosecond laser mounted on a two-photon microscope. The parameters for successful two-photon axotomy must be optimized for each microscope. We will demonstrate two-photon axotomy on both a custom built two-photon microscope and a Zeiss 510 confocal/two-photon to provide two examples.

Zebrafish trigeminal sensory neurons can be visualized in a transgenic line expressing GFP driven by a sensory neuron specific promoter 1. We have adapted this zebrafish trigeminal model to directly observe sensory axon regeneration in living zebrafish embryos. Embryos are anesthetized with tricaine and positioned within a drop of agarose as it solidifies. Immobilized embryos are sealed within an imaging chamber filled with phenylthiourea (PTU) Ringers. We have found that embryos can be continuously imaged in these chambers for 12-48 hours. A single confocal image is then captured to determine the desired site of axotomy. The region of interest is located on the two-photon microscope by imaging the sensory axons under low, non-damaging power. After zooming in on the desired site of axotomy, the power is increased and a single scan of that defined region is sufficient to sever the axon. Multiple location time-lapse imaging is then set up on a confocal microscope to directly observe axonal recovery from injury.

Here we describe a method for mounting zebrafish embryos for long-term imaging, two-photon imaging and tissue-damage techniques, and time-lapse confocal imaging.

Zebrafish have long been utilized to study the cellular and molecular mechanisms of development by time-lapse imaging of the living transparent embryo.  ...

Time-lapse Imaging of Mitosis After siRNA Transfection

Changes in cellular organization and chromosome dynamics that occur during mitosis are tightly coordinated to ensure accurate inheritance of genomic and cellular content. Hallmark events of mitosis, such as chromosome movement, can be readily tracked on an individual cell basis using time-lapse fluorescence microscopy of mammalian cell lines expressing specific GFP-tagged proteins. In combination with RNAi-based depletion, this can be a powerful method for pinpointing the stage(s) of mitosis where defects occur after levels of a particular protein have been lowered. In this protocol, we present a basic method for assessing the effect of depleting a potential mitotic regulatory protein on the timing of mitosis. Cells are transfected with siRNA, placed in a stage-top incubation chamber, and imaged using an automated fluorescence microscope. We describe how to use software to set up a time-lapse experiment, how to process the image sequences to make either still-image montages or movies, and how to quantify and analyze the timing of mitotic stages using a cell-line expressing mCherry-tagged histone H2B. Finally, we discuss important considerations for designing a time-lapse experiment. This strategy is complementary to other approaches and offers the advantages of 1) sensitivity to changes in kinetics that might not be observed when looking at cells as a population and 2) analysis of mitosis without the need to synchronize the cell cycle using drug treatments. The visual information from such imaging experiments not only allows the sub-stages of mitosis to be assessed, but can also provide unexpected insight that would not be apparent from cell cycle analysis by FACS.

Here we describe a basic protocol to image and quantify the mitotic timing of live mammalian tissue culture cells after siRNA transfection.

Changes in cellular organization and chromosome dynamics that occur during mitosis are tightly coordinated to ensure accurate inheritance of genomic and ...

Multicolor Time-lapse Imaging of Transgenic Zebrafish: Visualizing Retinal Stem Cells Activated by Targeted Neuronal Cell Ablation

High-resolution time-lapse imaging of living zebrafish larvae can be utilized to visualize how biological processes unfold (for review see 1). Compound transgenic fish which express different fluorescent reporters in neighboring cell types provide a means of following cellular interactions 2 and/or tissue-level responses to experimental manipulations over time. In this video, we demonstrate methods that can be used for imaging multiple transgenically labeled cell types serially in individual fish over time courses that can span from minutes to several days. The techniques described are applicable to any study seeking to correlate the "behavior" of neighboring cells types over time, including: 1) serial 'catch and release' methods for imaging a large number of fish over successive days, 2) simplified approaches for separating fluorophores with overlapping excitation/emission profiles (e.g., GFP and YFP), 3) use of hypopigmented mutant lines to extend the time window available for high-resolution imaging into late larval stages of development, 4) use of membrane targeted fluorescent reporters to reveal fine morphological detail of individual cells as well as cellular details in larger populations of cells, and 5) a previously described method for chemically-induced ablation of transgenically targeted cell types; i.e., nitroreductase (NTR) mediated conversion of prodrug substrates, such as metronidazole (MTZ), to cytotoxic derivatives 3,5.
As an example of these approaches, we will visualize the ablation and regeneration of a subtype of retinal bipolar neuron within individual fish over several days. Simultaneously we will monitor several other retinal cell types, including neighboring non-targeted bipolar cells and potential degeneration-stimulated retinal stem cells (i.e., M&#971;ller glia). This strategy is being applied in our lab to characterize cell- and tissue-level (e.g., stem cell niche) responses to the selective loss and regeneration of targeted neuronal cell types.

In this video, techniques for multicolor confocal time-lapse imaging and targeted cell ablation are provided. Time-lapse imaging is used to monitor the behavior of multiple cell types of interest in vivo. Targeted cell ablation facilitates the study neural circuit function and cell-specific neuronal regeneration paradigms.

High-resolution time-lapse imaging of living zebrafish larvae can be utilized to visualize how biological processes unfold (for review see 1). Compound ...

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes. The transparency of the 
embryos, the genetic resources, and the relative ease of transformation are qualities that make C. elegans an excellent model for early embryogenesis. Laser-based 
confocal microscopy and fluorescently labeled tags allow researchers to follow specific cellular structures and proteins in the developing embryo. For example, 
one can follow specific organelles, such as lysosomes or mitochondria, using fluorescently labeled dyes. These dyes can be delivered to the early embryo by means 
of microinjection into the adult gonad. Also, the localization of specific proteins can be followed using fluorescent protein tags. Examples are presented here 
demonstrating the use of a fluorescent lysosomal dye as well as fluorescently tagged histone and ubiquitin proteins. The labeled histone is used to visualize 
the DNA and thus identify the stage of the cell cycle. GFP-tagged ubiquitin reveals the dynamics of ubiquitinated vesicles in the early embryo. Observations 
of labeled lysosomes and GFP:: ubiquitin can be used to determine if there is colocalization between ubiquitinated vesicles and lysosomes. A technique for 
the microinjection of the lysosomal dye is presented. Techniques for generating transgenenic strains are presented elsewhere (1, 2). For imaging, embryos 
are cut out of adult hermaphrodite nematodes and mounted onto 2% agarose pads followed by time-lapse microscopy on a standard laser scanning confocal 
microscope or a spinning disk confocal microscope. This methodology provides for the high resolution visualization of early embryogenesis.

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

This article describes a technique for the visualization of the early events of embryogenesis in the nematode Caenorhabditis elegans.

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes.  The transparency of the 
embryos, the genetic ...

Quantitative Analysis of Random Migration of Cells Using Time-lapse Video Microscopy

Cell migration is a dynamic process, which is important for embryonic development, tissue repair, immune system function, and tumor invasion 1, 2. During directional migration, cells move rapidly in response to an extracellular chemotactic signal, or in response to intrinsic cues 3 provided by the basic motility machinery. Random migration occurs when a cell possesses low intrinsic directionality, allowing the cells to explore their local environment.
Cell migration is a complex process, in the initial response cell undergoes polarization and extends protrusions in the direction of migration 2. Traditional methods to measure migration such as the Boyden chamber migration assay is an easy method to measure chemotaxis in vitro, which allows measuring migration as an end point result. However, this approach neither allows measurement of individual migration parameters, nor does it allow to visualization of morphological changes that cell undergoes during migration.
Here, we present a method that allows us to monitor migrating cells in real time using video - time lapse microscopy. Since cell migration and invasion are hallmarks of cancer, this method will be applicable in studying cancer cell migration and invasion in vitro. Random migration of platelets has been considered as one of the parameters of platelet function 4, hence this method could also be helpful in studying platelet functions. This assay has the advantage of being rapid, reliable, reproducible, and does not require optimization of cell numbers. In order to maintain physiologically suitable conditions for cells, the microscope is equipped with CO2 supply and temperature thermostat. Cell movement is monitored by taking pictures using a camera fitted to the microscope at regular intervals. Cell migration can be calculated by measuring average speed and average displacement, which is calculated by Slidebook software.

This method allows monitoring of cells in real time and quantitative measurements of different cell migration parameters such as speed, displacement, and velocity. Unlike the traditional methods, this real time approach is not based on endpoint quantitative migration measurements; instead it allows monitoring and calculating different parameters continuously.

Cell migration is a dynamic process, which is important for embryonic development, tissue repair, immune system function, and tumor invasion 1, 2. During ...

Long-term, High-resolution Confocal Time Lapse Imaging of Arabidopsis Cotyledon Epidermis during Germination

Imaging in vivo dynamics of cellular behavior throughout a developmental sequence can be a powerful technique for understanding the mechanics of tissue patterning. During animal development, key cell proliferation and patterning events occur very quickly. For instance, in Caenorhabditis elegans all cell divisions required for the larval body plan are completed within six hours after fertilization, with seven mitotic cycles1; the sixteen or more mitoses of Drosophila embryogenesis occur in less than 24 hr2. In contrast, cell divisions during plant development are slow, typically on the order of a day 3,4,5 . This imposes a unique challenge and a need for long-term live imaging for documenting dynamic behaviors of cell division and differentiation events during plant organogenesis. Arabidopsis epidermis is an excellent model system for investigating signaling, cell fate, and development in plants. In the cotyledon, this tissue consists of air- and water-resistant pavement cells interspersed with evenly distributed stomata, valves that open and close to control gas exchange and water loss. Proper spacing of these stomata is critical to their function, and their development follows a sequence of asymmetric division and cell differentiation steps to produce the organized epidermis (Fig. 1).
This protocol allows observation of cells and proteins in the epidermis over several days of development. This time frame enables precise documentation of stem-cell divisions and differentiation of epidermal cells, including stomata and epidermal pavement cells. Fluorescent proteins can be fused to proteins of interest to assess their dynamics during cell division and differentiation processes. This technique allows us to understand the localization of a novel protein, POLAR6, during the proliferation stage of stomatal-lineage cells in the Arabidopsis cotyledon epidermis, where it is expressed in cells preceding asymmetric division events and moves to a characteristic area of the cell cortex shortly before division occurs. Images can be registered and streamlined video easily produced using public domain software to visualize dynamic protein localization and cell types as they change over time.

Long-term, High-resolution Confocal Time Lapse Imaging of Arabidopsis Cotyledon Epidermis during Germination

We describe a protocol using chamber slides and media to immobilize plant cotyledons for confocal imaging of the epidermis over several days of development, documenting stomatal differentiation. Fluorophore-tagged proteins can be tracked dynamically by expression and subcellular localization, increasing understanding of their possible roles during cell division and cell-type differentiation.

Imaging in vivo dynamics of cellular behavior throughout a developmental sequence can be a powerful technique for understanding the mechanics of tissue ...

Super-resolution Imaging of the Bacterial Division Machinery

Bacterial cell division requires the coordinated assembly of more than ten essential proteins at midcell1,2. Central to this process is the formation of a ring-like suprastructure (Z-ring) by the FtsZ protein at the division plan3,4. The Z-ring consists of multiple single-stranded FtsZ protofilaments, and understanding the arrangement of the protofilaments inside the Z-ring will provide insight into the mechanism of Z-ring assembly and its function as a force generator5,6. This information has remained elusive due to current limitations in conventional fluorescence microscopy and electron microscopy. Conventional fluorescence microscopy is unable to provide a high-resolution image of the Z-ring due to the diffraction limit of light (~200 nm). Electron cryotomographic imaging has detected scattered FtsZ protofilaments in small C. crescentus cells7, but is difficult to apply to larger cells such as E. coli or B. subtilis. Here we describe the application of a super-resolution fluorescence microscopy method, Photoactivated Localization Microscopy (PALM), to quantitatively characterize the structural organization of the E. coli Z-ring8.
	PALM imaging offers both high spatial resolution (~35 nm) and specific labeling to enable unambiguous identification of target proteins. We labeled FtsZ with the photoactivatable fluorescent protein mEos2, which switches from green fluorescence (excitation = 488 nm) to red fluorescence (excitation = 561 nm) upon activation at 405 nm9. During a PALM experiment, single FtsZ-mEos2 molecules are stochastically activated and the corresponding centroid positions of the single molecules are determined with &lt;20 nm precision. A super-resolution image of the Z-ring is then reconstructed by superimposing the centroid positions of all detected FtsZ-mEos2 molecules.
	Using this method, we found that the Z-ring has a fixed width of ~100 nm and is composed of a loose bundle of FtsZ protofilaments that overlap with each other in three dimensions. These data provide a springboard for further investigations of the cell cycle dependent changes of the Z-ring10 and can be applied to other proteins of interest.

We describe a super-resolution imaging method to probe the structural organization of the bacterial FtsZ-ring, an essential apparatus for cell division. This method is based on quantitative analyses of photoactivated localization microscopy (PALM) images and can be applied to other bacterial cytoskeletal proteins.

Bacterial cell division requires the coordinated  assembly of more than ten essential proteins at midcell1,2. Central  to this process is the formation of ...

Visualization of Craniofacial Development in the sox10: kaede Transgenic Zebrafish Line Using Time-lapse Confocal Microscopy

Vertebrate palatogenesis is a highly choreographed and complex developmental process, which involves migration of cranial neural crest (CNC) cells, convergence and extension of facial prominences, and maturation of the craniofacial skeleton. To study the contribution of the cranial neural crest to specific regions of the zebrafish palate a sox10: kaede transgenic zebrafish line was generated. Sox10 provides lineage restriction of the kaede reporter protein to the neural crest, thereby making the cell labeling a more precise process than traditional dye or reporter mRNA injection. Kaede is a photo-convertible protein that turns from green to red after photo activation and makes it possible to follow cells precisely. The sox10: kaede transgenic line was used to perform lineage analysis to delineate CNC cell populations that give rise to maxillary versus mandibular elements and illustrate homology of facial prominences to amniotes. This protocol describes the steps to generate a live time-lapse video of a sox10: kaede zebrafish embryo. Development of the ethmoid plate will serve as a practical example. This protocol can be applied to making a time-lapse confocal recording of any kaede or similar photoconvertible reporter protein in transgenic zebrafish. Furthermore, it can be used to capture not only normal, but also abnormal development of craniofacial structures in the zebrafish mutants.

Visualization of experimental data has become a key element in presenting results to the scientific community. Generation of live time-lapse recording of growing embryos contributes to better presentation and understanding of complex developmental processes. This protocol is a step-by-step guide to cell labeling via photoconversion of kaede protein in zebrafish.

Vertebrate palatogenesis is a highly choreographed and complex developmental process, which involves migration of cranial neural crest (CNC) cells, ...

High-resolution Time-lapse Imaging and Automated Analysis of Microtubule Dynamics in Living Human Umbilical Vein Endothelial Cells

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes within individual endothelial cells (ECs). These processes are critical for homeostatic maintenance such as wound healing, and are also crucial in promoting tumor growth and metastasis. EC morphology is defined by the organization of the cytoskeleton, a tightly regulated system of actin and microtubule (MT) dynamics that is known to control EC branching, polarity and directional migration, essential components of angiogenesis. To study MT dynamics, we used high-resolution fluorescence microscopy coupled with computational image analysis of fluorescently-labeled MT plus-ends to investigate MT growth dynamics and the regulation of EC branching morphology and directional migration. Time-lapse imaging of living Human Umbilical Vein Endothelial Cells (HUVECs) was performed following transfection with fluorescently-labeled MT End Binding protein 3 (EB3) and Mitotic Centromere Associated Kinesin (MCAK)-specific cDNA constructs to evaluate effects on MT dynamics. PlusTipTracker software was used to track EB3-labeled MT plus ends in order to measure MT growth speeds and MT growth lifetimes in time-lapse images. This methodology allows for the study of MT dynamics and the identification of how localized regulation of MT dynamics within sub-cellular regions contributes to the angiogenic processes of EC branching and migration.

Protocols for Human Umbilical Vein Endothelial Cell (HUVEC) culture, transient transfection of fluorescently-labeled markers of microtubule growth, live-cell imaging and automated analysis of interphase microtubule growth dynamics are detailed.

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes ...