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 ...

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