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.

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