The authors would like to acknowledge Dr. Wade Sigurdson for providing valuable input in the design of the flow apparatus.

1. Assemble the Flow Apparatus
<ol>
	<li>Configure the parts listed in the Table of Materials according to the schematic in Figure 1 with the considerations discussed below. 
	NOTE: For convenience, the flow apparatus is divided into two sides, the green side (everything upstream of the slide to the media flasks), and the orange side (everything downstream of the slide to the media flasks).
	<ol>
		<li>Ensure that all of the flow apparatus is air tight to prevent leak...

<ol>
	<li>Pankhurst, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candidiasis+(oropharyngeal).">Candidiasis (oropharyngeal).</a> BMJ clinical evidence. 2012, 1304 (2012).</li><li>Ramage, G., Vandewalle, K., Wickes, B. L., L&#243;pez-Ribot, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+biofilm+formation+by+Candida+albicans.">Characteristics of biofilm formation by Candida albicans.</a> Revista iberoamericana de micolog&#237;a. 18 (4), 163-170 (2001).</li><li>Nobile, C. J., Mitchell, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+cell-surface+genes+and+biofilm+formation+by+the+C.+albicans+transcription+factor+Bcr1p.">Regulation of cell-surface genes and biofilm formation by the C. albicans transcription factor Bcr1p.</a> Current biology: CB. 15 (12), 1150-1155 (2005).</li><li>Blankenship, J. R., Mitchell, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+build+a+biofilm:+a+fungal+perspective.">How to build a biofilm: a fungal perspective.</a> Current opinion in microbiology. 9 (6), 588-594 (2006).</li><li>Ara&#250;jo, D., Henriques, M., Silva, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Portrait+of+Candida+Species+Biofilm+Regulatory+Network+Genes.">Portrait of Candida Species Biofilm Regulatory Network Genes.</a> Trends in microbiology. 25 (1), 62-75 (2017).</li><li>Lane, W. O., 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=Parallel-plate+flow+chamber+and+continuous+flow+circuit+to+evaluate+endothelial+progenitor+cells+under+laminar+flow+shear+stress.">Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress.</a> Journal of visualized experiments. (59), e3349 (2012).</li><li>Bakker, D. P., van der Plaats, A., Verkerke, G. J., Busscher, H. J., van der Mei, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+velocity+profiles+for+different+flow+chamber+designs+used+in+studies+of+microbial+adhesion+to+surfaces.">Comparison of velocity profiles for different flow chamber designs used in studies of microbial adhesion to surfaces.</a> Applied and environmental microbiology. 69 (10), 6280-6287 (2003).</li><li>Zhang, W., Sileika, T. S., Chen, C., Liu, Y., Lee, J., Packman, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+planar+flow+cell+for+studies+of+biofilm+heterogeneity+and+flow-biofilm+interactions.">A novel planar flow cell for studies of biofilm heterogeneity and flow-biofilm interactions.</a> Biotechnology and bioengineering. 108 (11), 2571-2582 (2011).</li><li>Uppuluri, P., Lopez-Ribot, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+easy+and+economical+in+vitro+method+for+the+formation+of+Candida+albicans+biofilms+under+continuous+conditions+of+flow.">An easy and economical in vitro method for the formation of Candida albicans biofilms under continuous conditions of flow.</a> Virulence. 1 (6), 483-487 (2010).</li><li>Diaz, P. I., 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=Synergistic+interaction+between+Candida+albicans+and+commensal+oral+streptococci+in+a+novel+in+vitro+mucosal+model.">Synergistic interaction between Candida albicans and commensal oral streptococci in a novel in vitro mucosal model.</a> Infection and immunity. 80 (2), 620-632 (2012).</li><li>McCall, A., Edgerton, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-Time+Approach+to+Flow+Cell+Imaging+of+Candida+albicans+Biofilm+Development.">Real-Time Approach to Flow Cell Imaging of Candida albicans Biofilm Development.</a> Journal of fungi. 3 (1), 13 (2017).</li><li>Zhang, B., Zerubia, J., Olivo-Marin, 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=Gaussian+approximations+of+fluorescence+microscope+point-spread+function+models.">Gaussian approximations of fluorescence microscope point-spread function models.</a> Applied optics. 46 (10), 1819-1829 (2007).</li><li>Tati, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candida+glabrata+Binding+to+Candida+albicans+Hyphae+Enables+Its+Development+in+Oropharyngeal+Candidiasis.">Candida glabrata Binding to Candida albicans Hyphae Enables Its Development in Oropharyngeal Candidiasis.</a> PLoS pathogens. 12 (3), 1005522 (2016).</li></ol>

Using the flow system as outlined above allows for the generation of quantitative time-lapse videos of fungal biofilm growth and development. To allow for comparisons between experiments it is of critical importance to ensure that the imaging parameters are kept the same. This includes ensuring that the microscope is set up for K&#246;hler illumination for each experiment (many guides are available online for this process). Aside from imaging parameters, there are some important steps to keep in mind when working with th...

Candida albicans (C. albicans) is an opportunistic fungal pathogen of humans that can infect many tissue types, including oral mucosal surfaces, causing oropharyngeal candidiasis and resulting in a lower quality of life for affected individuals1. Biofilm formation is an important characteristic for the pathogenesis of C. albicans, and numerous studies have been done on the formation and function of C. albicans biofilms2,3,4,5, many of which have been conducted using static (no flow) in vitro models. However, C. albicans must adhere and grow in the presence of salivary flow in the oral cavity. Numerous flow systems have been developed to allow for live-cell imaging6,7,8,9,10. These different flow systems have been designed for different purposes, and therefore each system has different strengths and weaknesses. We found that many of the flow systems appropriate for C. albicans were costly, required complex fabricated parts, or could not be imaged during flow and had to be stopped prior to imaging. Therefore, we developed a novel flow apparatus to study C. albicans biofilm formation under flow11. During the design of our flow apparatus, we followed these major considerations. First, we wanted to be able to quantify multiple aspects of the biofilm growth and development in real-time without requiring the use of fluorescent cells (allowing us to study mutant strains and unmodified clinical isolates easily). Second, we wanted all parts to be commercially available with little to no modifications (i.e., no custom fabrication), allowing others to more easily recreate our system, and allowing for easy repairs. Third, we also wanted to allow for extended imaging times at reasonably high flow rates. Lastly, we wanted, following a period of cells attaching to the substrate under flow, to be able to monitor the biofilm growth over an extended time without introducing new cells.
These considerations led us to develop the two-flask recirculating flow system illustrated in Figure 1. The two flasks allow us to split the experiment into two phases, an attachment phase that draws from the cell-seeded attachment flask, and a growth phase that uses cell-free media to continue the biofilm growth without the addition of new cells. This system is designed to work with an incubation chamber for the microscope, with the slide and the tubing preceding it (2 to 5,&#160;Figure 1) being placed inside the incubator, and all other components placed in a large secondary container outside the microscope. Additionally, a hotplate stirrer with an attached temperature probe is used to maintain fungal cells in the attachment flask at 37 &#176;C. As it is recirculating, this system is capable of continuous imaging during flow (can be over 36 h depending on conditions), and can be used on most standard microscopes, including upright or inverted benchtop microscopes. Here, we discuss the assembly, operation, and cleaning of the flow apparatus, as well as provide some basic ImageJ quantitative algorithms to analyze the videos after an experiment.

<table border="0" cellpadding="0" cellspacing="0" style="width:635px;" width="635">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Pump</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">07522-20</td>
			<td style="width:229px;">6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Pump head</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">77200-60</td>
			<td>6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Tubing</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">96410-14</td>
			<td>N/A</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Bubble trap adapter</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">30704-84</td>
			<td>3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Bubble trap vacuum adapter for 1/4&#8221; ID vacuum line</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">31500-55</td>
			<td>3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">In-line filter adapter (4 needed)</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">31209-40</td>
			<td>8,9</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Orange-side Y</td>
			<td style="width:71px;">Cole Parmer</td>
			<td style="width:119px;">31209-55</td>
			<td>7</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Green-side Y</td>
			<td style="width:71px;">ibidi</td>
			<td style="width:119px;">10827</td>
			<td>2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">* Slides</td>
			<td style="width:71px;">ibidi</td>
			<td style="width:119px;">80196</td>
			<td>4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">* Slide luers</td>
			<td style="width:71px;">ibidi</td>
			<td style="width:119px;">10802</td>
			<td>4</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Vacuum assisted Bubble trap</td>
			<td style="width:71px;">Elveflow/Darwin microfluidics</td>
			<td style="width:119px;">KBTLarge - Microfluidic Bubble Trap Kit</td>
			<td>3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Media flasks</td>
			<td style="width:71px;">Corning</td>
			<td style="width:119px;">4980-500</td>
			<td>1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">0.2 &#181;m air filter</td>
			<td style="width:71px;">Corning</td>
			<td style="width:119px;">431229</td>
			<td>1</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Threaded glass bottle for PD and filter flask (2 needed)</td>
			<td style="width:71px;">Corning</td>
			<td style="width:119px;">1395-100</td>
			<td>5,10</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ported Screw cap for PD and filter flask (2 needed)</td>
			<td style="width:71px;">Wheaton</td>
			<td style="width:119px;">1129750</td>
			<td>5,10</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Screwcap tubing connector</td>
			<td style="width:71px;">Wheaton</td>
			<td style="width:119px;">1129814</td>
			<td>5,10</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Tubing connector beveled washer</td>
			<td style="width:71px;">Danco</td>
			<td style="width:119px;">88579</td>
			<td>5,10</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tubing connector flat washer</td>
			<td style="width:71px;">Danco</td>
			<td style="width:119px;">88569</td>
			<td>5,10</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Clamps for in-line filters and downstream Y (7 needed)</td>
			<td style="width:71px;">Oetiker/MSC Industrial Supply Company</td>
			<td style="width:119px;">15100002-100</td>
			<td>7,8,9</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Clamp tool</td>
			<td style="width:71px;">Oetiker/MSC Industrial Supply Company</td>
			<td style="width:119px;">14100386</td>
			<td>N/A</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">20 micron in-line media filter</td>
			<td style="width:71px;">Analytical Scientific Instruments</td>
			<td style="width:119px;">850-1331</td>
			<td>8</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">10 micron in-line media filter</td>
			<td style="width:71px;">Analytical Scientific Instruments</td>
			<td style="width:119px;">850-1333</td>
			<td>9</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">2 micron inlet media filter</td>
			<td style="width:71px;">Supelco/Sigma-Aldrich</td>
			<td style="width:119px;">58267</td>
			<td>10</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">* 0.22 &#181;m media filter</td>
			<td style="width:71px;">Millipore</td>
			<td style="width:119px;">SVGV010RS</td>
			<td>11</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">* 0.22 &#181;m media filter &#8220;adapter&#8221;</td>
			<td style="width:71px;">BD Biosciences</td>
			<td style="width:119px;">329654</td>
			<td>11</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Rubber stopper</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">14-131E</td>
			<td>1</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Hotplate stirrer with external probe port</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td style="width:119px;">88880006</td>
			<td>N/A</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Temperature probe</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td style="width:119px;">88880147</td>
			<td>N/A</td>
		</tr>
	</tbody>
</table>

real-time imaging and quantification of fungal biofilm development using a two-phase recirculating flow system

In oropharyngeal candidiasis, members of the genus Candida must adhere to and grow on the oral mucosal surface while under the effects of salivary flow. While models for the growth under flow have been developed, many of these systems are expensive, or do not allow imaging while the cells are under flow. We have developed a novel apparatus that allows us to image the growth and development of Candida albicans cells under flow and in real-time. Here, we detail the protocol for the assembly and use of this flow apparatus, as well as the quantification of data that are generated. We are able to quantify the rates that the cells attach to and detach from the slide, as well as to determine a measure of the biomass on the slide over time. This system is both economical and versatile, working with many types of light microscopes, including inexpensive benchtop microscopes, and is capable of extended imaging times compared to other flow systems. Overall, this is a low-throughput system that can provide highly detailed real-time information on the biofilm growth of fungal species under flow.

Representative images of a normal overnight time-lapse experiment using wild-type C. albicans cells at 37 &#176;C can be seen in Figure 2A and Supplemental Video 1. The images have been contrast enhanced to improve visibility. Quantification of the original data was performed, and representative graphs can be seen in Figure 2B. To generate these graphs, the data were fir...

Watch this Scientific Journal Video about Real-time Imaging and Quantification of Fungal Biofilm Development Using a Two-Phase Recirculating Flow System at JoVE.com

Real-time Imaging and Quantification of Fungal Biofilm Development Using a Two-Phase Recirculating Flow System

We describe the assembly, operation, and cleaning of a flow apparatus designed to image fungal biofilm formation in real time while under flow. We also provide and discuss quantitative algorithms to be used on the acquired images.

In oropharyngeal candidiasis, members of the genus Candida must adhere to and grow on the oral mucosal surface while under the effects of salivary flow. ...

This method can help answer key questions in the microbiology field, such as how fluid flow alters fungal biofilm growth and development. The main advantage of this technique is it allows us to quantitatively evaluate the effects of flow on biofilm growth and development in real time. Begin this experiment with assembly of the flow apparatus, as described in the text protocol.The day of the experiment, attach the bubble trap, temperature probe, and all single use components. To assemble the filter, remove the plunger from a one-milliliter syringe to make it an adapter. Force the tubing from the filter bottle into this end and attach a 2 micron filter to the tubing leading to the growth flask.Apply silicone vacuum grease around the barb of the slide adapter prior to connecting it, as this helps prevent air leaks into the system. Fill the attachment flask with 100 milliliters of YPD, and fill the growth flask with 200 milliliters of YPD. Ensure that the green side tubing reaches the media in each flask.Ensure that all valves are open. Attach the bubble trap to a vacuum, and connect the pump to the green side tubing downstream of the bubble trap. Pump the fluid at a flow rate of 3.3 milliliters per minute to completely fill the green side.Then, dispense and discard approximately one to two milliliters of the media, because the first couple of milliliters often contain dead cells or random debris. Ensure that the green side of the tubing is filled with media and has no bubbles downstream of the bubble trap before proceeding. Fill the channel slide and the reservoir with YPD, taking care not to introduce bubbles.Connect the slide to the flow apparatus. Then pump more fluid to create a buffer of about 5 meters on the orange side. This is to prevent accidentally trapping air in the slide in the event of backflow.Now, prepare the flow apparatus for transport to the microscope by first planting the inlet and outlet of the bubble trap closed. Then clamp the green and orange side attachment flask valves closed. Ensure that the screw caps for the pulsation dampener and filter bottle are tight, as they can loosen during autoplating.Disconnect the pump from the tubing to make transport easier. Then move all components, including the hot plate stirrer, into a secondary container near the microscope. Attach the temperature probe to the hot plate stirrer, and begin heating the attachment flask to 37 degrees Celsius.Stir the media at 300 RPM, and maintain this for the entire experiment. Mount the slide on the microscope, and use tape if necessary to tightly secure it. Then attach the bubble trap to a vacuum.Now, connect the pump to the flow apparatus. Start the pump at a flow rate of 3.3 milliliters per minute, and allow it to run for approximately five to 10 seconds. Then, remove the bubble trap in let-out lid clan.Allow the pump to continue running while the attachment flask heats up. Once the attachment flask and incubation chamber are both at 37 degrees Celsius, add enough overnight culture of the fungal cells to the attachment flask to reach one million cells per milliliter. Wait 15 minutes to allow the cells to acclimate.Open both green and orange side attachment flask valves while closing both growth flask valves to start the flow of cells. Wait for approximately five minutes to allow cells to reach the slide. During this time, focus the microscope and adjust it to the same imaging parameters used in previous experiments.Begin image acquisition for the attachment phase. Check back after approximately five and 10 minutes to ensure that focus has been maintained. If not, attempt to adjust the focus immediately after the next image is acquired.Immediately after the attachment phase is finished, save the file. Then open both green and orange side growth flask valves while closing both attachment flask valves. Take care not to bump the stage if any valves are inside the incubation chamber.Unplug the thermometer probe, and replace the attachment flask with the growth flask. Now, configure the software to acquire an image every 15 minutes over 22 hours, and begin image acquisition for the growth phase. Once the growth phase acquisition has finished and the file has been saved, open the green and orange side attachment flask valves, which may make a noise as the pressure releases on the orange side.Pull up on the green side tubing coming from both media flasks, until they are at least several centimeters above the media. Then, run the pump at a high speed to remove all the media from the tubing, which makes cleaning much easier. Finally, quantify the videos as described in the text protocol.This time lapse dark field microscopy video shows the attachment of wild type Candida albican cells to the substrate underflow during the attachment phase, followed by the subsequent growth and development during the growth phase leading to biofilm formation. The data from these videos can be analyzed for the rates of cell attachment and detachment and biomass over time, shown here is the total biomass within the imaging region as determined by densitometry analysis. The cumulative rate of cell attachment and the percent biomass detachment over time are also shown.While attempting this procedure, it's important to remember to use the same imaging conditions across all experiments, as this allows for quantitative comparisons to be made between them.

real-time-imaging-quantification-fungal-biofilm-development-using-two

Research

JoVE Journal

Immunology and Infection

5.4K ビュー.  University at Buffalo. この方法は、流体の流れが真菌バイオフィルムの成長と発達をどのように変化させるかなど、微生物学分野の重要な質問に答えるのに役立ちます。この技術の主な利点は、リアルタイムでのバイオフィルムの成長と開発に対する流れの影響を定量的に評価できることです。テキストプロトコルに記載されているように、フロー装置の組み立てからこの実験を開始する。

ビデオ: Real-time Imaging and Quantification of Fungal Biofilm Development Using a Two-Phase Recirculating Flow System

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &beta;-arrestin

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to intracellular responses. GPCRs control diverse biological functions such as chemotaxis, intracellular calcium release, gene regulation in a ligand dependent manner via heterotrimeric G-proteins1-2. Ligand binding induces a series of conformational changes leading to activation of heterotrimeric G-proteins that modulate levels of second messengers such as cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3) and diacyl glycerol (DG). Concomitant with activation of the receptor ligand binding also initiates a series of events to attenuate the receptor signaling via desensitization, sequestration and/or internalization. The desensitization process of GPCRs occurs via receptor phosphorylation by G-protein receptor kinases (GRKs) and subsequent binding of &beta;-arrestins3. &beta;-arrestins are cytosolic proteins and translocate to membrane upon GPCR activation, binding to phosphorylated receptors (most cases) there by facilitating receptor internalization 4-6.
Leukotriene B4 (LTB4) is a pro-inflammatory lipid molecule derived from arachidonic acid pathway and mediates its actions via GPCRs, LTB4 receptor 1 (BLT1; a high affinity receptor) and LTB4 receptor 2 (BLT2; a low affinity receptor)7-9. The LTB4-BLT1 pathway has been shown to be critical in several inflammatory diseases including, asthma, arthritis and atherosclerosis10-17. The current paper describes the methodologies developed to monitor LTB4-induced leukocyte migration and the interactions of BLT1 with &beta;-arrestin and , receptor translocation in live cells using microscopy imaging techniques18-19.
Bone marrow derived dendritic cells from C57BL/6 mice were isolated and cultured as previously described 20-21. These cells were tested in live cell imaging methods to demonstrate LTB4 induced cell migration. The human BLT1 was tagged with red fluorescent protein (BLT1-RFP) at C-terminus and &beta;-arrestin1 tagged with green fluorescent protein (&beta;-arr-GFP) and transfected the both plasmids into Rat Basophilic Leukomia (RBL-2H3) cell lines18-19. The kinetics of interaction between these proteins and localization were monitored using live cell video microscopy. The methodologies in the current paper describe the use of microscopic techniques to investigate the functional responses of G-protein coupled receptors in live cells. The current paper also describes the use of Metamorph software to quantify the fluorescence intensities to determine the kinetics of receptor and cytosolic protein interactions.

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &amp;#946;-arrestin

This paper describes the methodology to determine the chemotactic response of leukocytes to specific ligands and identify interactions between the cell surface receptors and cytosolic proteins using live cell imaging techniques.

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to ...

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological properties compared to free living microorganisms. Biofilms in nature are often difficult to investigate and reside under poorly defined conditions1. Using a transparent substratum it is possible to device a system where simple biofilms can be examined in a non-destructive way in real-time: here we demonstrate the assembly and operation of a flow cell model system, for in vitro 3D studies of microbial biofilms generating high reproducibility under well-defined conditions2,3.
The system consists of a flow cell that serves as growth chamber for the biofilm. The flow cell is supplied with nutrients and oxygen from a medium flask via a peristaltic pump and spent medium is collected in a waste container. This construction of the flow system allows a continuous supply of nutrients and administration of e.g. antibiotics with minimal disturbance of the cells grown in the flow chamber. Moreover, the flow conditions within the flow cell allow studies of biofilm exposed to shear stress. A bubble trapping device confines air bubbles from the tubing which otherwise could disrupt the biofilm structure in the flow cell.
The flow cell system is compatible with Confocal Laser Scanning Microscopy (CLSM) and can thereby provide highly detailed 3D information about developing microbial biofilms. Cells in the biofilm can be labeled with fluorescent probes or proteins compatible with CLSM analysis. This enables online visualization and allows investigation of niches in the developing biofilm. Microbial interrelationship, investigation of antimicrobial agents or the expression of specific genes, are of the many experimental setups that can be investigated in the flow cell system.

Pseudomonas aeruginosa and Saccharomyces cerevisiae Biofilm in Flow Cells

Protocol describing the application of a flow cell system for growing and analyzing microbial biofilms for Confocal Laser Scanning Microscopy (CLSM).

Many microbial cells have the ability to form sessile microbial communities defined as biofilms that have altered physiological and pathological ...

Development of a Negative Selectable Marker for Entamoeba histolytica

Entamoeba histolytica is the causative agent of amebiasis and infects up to 10% of the world's population. The molecular techniques that have enabled the up- and down-regulation of gene expression rely on the transfection of stably maintained plasmids. While these have increased our understanding of Entamoeba virulence factors, the capacity to integrate exogenous DNA into genome, which would allow reverse genetics experiments, would be a significant advantage in the study of this parasite. The challenges presented by this organism include inability to select for homologous recombination events and difficulty to cure episomal plasmid DNA from transfected trophozoites. The later results in a high background of exogenous DNA, a major problem in the identification of trophozoites in which a bona fide genomic integration event has occurred. We report the development of a negative selection system based upon transgenic expression of a yeast cytosine deaminase and uracil phosphoribosyl transferase chimera (FCU1) and selection with prodrug 5-fluorocytosine (5-FC). The FCU1 enzyme converts non-toxic 5-FC into toxic 5-fluorouracil and 5-fluorouridine-5'-monophosphate. E. histolytica lines expressing FCU1 were found to be 30 fold more sensitive to the prodrug compared to the control strain.

Development of a Negative Selectable Marker for Entamoeba histolytica

We report development of a negative selection system in E. histolytica based upon transgenic expression of a chimeric protein (FCU1) and selection with the prodrug 5-fluorocytosine. The FCU1 protein is a fusion of yeast cytosine deaminase and uracil phosphoribosyltransferase. Expression of FCU1 resulted in increased E. histolytica sensitivity towards 5-fluorocytosine.

Entamoeba histolytica is the causative agent of amebiasis and infects up to 10% of the world's population. The molecular techniques that have enabled the ...

Quantification of Fungal Colonization, Sporogenesis, and Production of Mycotoxins Using Kernel Bioassays

The rotting of grains by seed-infecting fungi poses one of the greatest economic challenges to cereal production worldwide, not to mention serious risks to human and animal health. Among cereal production, maize is arguably the most affected crop, due to pathogen-induced losses in grain integrity and mycotoxin seed contamination. The two most prevalent and problematic mycotoxins for maize growers and food and feed processors are aflatoxin and fumonisin, produced by Aspergillus flavus and Fusarium verticillioides, respectively.
Recent studies in molecular plant-pathogen interactions have demonstrated promise in understanding specific mechanisms associated with plant responses to fungal infection and mycotoxin contamination1,2,3,4,5,6. Because many labs are using kernel assays to study plant-pathogen interactions, there is a need for a standardized method for quantifying different biological parameters, so results from different laboratories can be cross-interpreted. For a robust and reproducible means for quantitative analyses on seeds, we have developed in-lab kernel assays and subsequent methods to quantify fungal growth, biomass, and mycotoxin contamination. Four sterilized maize kernels are inoculated in glass vials with a fungal suspension (106) and incubated for a predetermined period. Sample vials are then selected for enumeration of conidia by hemocytometer, ergosterol-based biomass analysis by high performance liquid chromatography (HPLC), aflatoxin quantification using an AflaTest fluorometer method, and fumonisin quantification by HPLC.

The devastation of cereal crops by seed-infecting fungi has prompted numerous research efforts to better understand plant-pathogen interactions. To study seed-fungal interactions in a laboratory setting, we developed a robust method for the quantification of fungal reproduction, biomass, and mycotoxin contamination using kernel bioassays.

The rotting of grains by seed-infecting fungi poses one of the greatest economic challenges to cereal production worldwide, not to mention serious risks ...

A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

Signaling is initiated through the T Cell Receptor (TCR) when it is engaged by antigenic peptide fragments bound by Major Histocompatibility Complex (pMHC) proteins expressed on the surface of antigen presenting cells (APCs). The TCR complex is composed of the ligand binding TCR&alpha;&beta; heterodimer that associates non-covalently with CD3 dimers (the &#949;&delta; and &#949;&gamma; heterodimers and the &zeta;&zeta; homodimer)1. Upon engagement of the receptor, the CD3 &zeta; chains are phosphorylated by the Src family kinase, Lck. This leads to the recruitment of the Syk family kinase, Zap70, which is then phosphorylated and activated by Lck. After that, Zap70 phosphorylates the adapter proteins LAT and SLP76, initiating the formation of the proximal signaling complex containing a large number of different signaling molecules2. 
The formation of this complex eventually results in calcium and Ras-dependent transcription factor activation and the consequent initiation of a complex series of gene expression programs that give rise to T cell differentiation2. TCR signals (and the resulting state of differentiation) are modulated by many other factors, including antigen potency and crosstalk with co-stimulatory/co-inhibitory, chemokine, and cytokine receptors 3-4. Studying the spatial and temporal organization of the proximal signaling complex under various stimulation conditions is, therefore, key to understanding the TCR signaling pathway as well as its regulation by other signaling pathways.
One very useful model system to study signaling initiated by the TCR at the plasma membrane in T cells is glass-supported lipid bilayers, as described previously5-6. They can be utilized to present antigenic pMHC complexes, adhesion, and co-stimulatory molecules to T cells-serving as artificial APCs. By imaging the T cells interacting with the lipid bilayer using total internal reflection fluorescence microscopy (TIRFM), we can restrict the excitation to within 100 nm of the space between the glass and the cell surface 7-8. This allows us to image primarily the signaling events occurring at the plasma membrane. As we are interested in imaging the recruitment of signaling proteins to the TCR complex, we describe a two-camera TIRF imaging system wherein the TCR, labeled with fluorescent Fab (fragment antigen binding) fragments of the H57 antibody (purified from hybridoma H57-597, ATCC, ATCC Number:HB-218) which is specific for TCR&beta;, and signaling proteins, tagged with GFP, may be imaged simultaneously and in real time. This strategy is necessary due to the highly dynamic nature of both the T cells and of the signaling events that are occurring at the TCR. This imaging modality has allowed researchers to image single ligands 9-11 as well as recruitment of signaling molecules to activated receptors and is an excellent system to study biochemistry in-situ12-16.

The compartmentalization of proteins either within the plasma membrane or into intracellular locations is one regulatory mechanism that can greatly influence signaling outcomes; hence, to understand signaling it is important to study the spatial and temporal behavior of the proteins involved. We describe here a TIRF microscopy based system to study signal transduction in T cells, but is broadly applicable.

Signaling is initiated through the T Cell Receptor (TCR) when it is engaged by antigenic peptide fragments bound by Major Histocompatibility Complex ...

Real-time Live Imaging of T-cell Signaling Complex Formation

Protection against infectious diseases is mediated by the immune system 1,2. T lymphocytes are the master coordinators of the immune system, regulating the activation and responses of multiple immune cells 3,4. T-cell activation is dependent on the recognition of specific antigens displayed by antigen presenting cells (APCs). The T-cell antigen receptor (TCR) is specific to each T-cell clone and determines antigen specificity 5. The binding of the TCR to the antigen induces the phosphorylation of components of the TCR complex. In order to promote T-cell activation, this signal must be transduced from the membrane to the cytoplasm and the nucleus, initiating various crucial responses such as recruitment of signaling proteins to the TCR;APC site (the immune synapse), their molecular activation, cytoskeletal rearrangement, elevation of intracellular calcium concentration, and changes in gene expression 6,7. The correct initiation and termination of activating signals is crucial for appropriate T-cell responses. The activity of signaling proteins is dependent on the formation and termination of protein-protein interactions, post translational modifications such as protein phosphorylation, formation of protein complexes, protein ubiquitylation and the recruitment of proteins to various cellular sites 8. Understanding the inner workings of the T-cell activation process is crucial for both immunological research and clinical applications.
Various assays have been developed in order to investigate protein-protein interactions; however, biochemical assays, such as the widely used co-immunoprecipitation method, do not allow protein location to be discerned, thus precluding the observation of valuable insights into the dynamics of cellular mechanisms. Additionally, these bulk assays usually combine proteins from many different cells that might be at different stages of the investigated cellular process. This can have a detrimental effect on temporal resolution. The use of real-time imaging of live cells allows both the spatial tracking of proteins and the ability to temporally distinguish between signaling events, thus shedding light on the dynamics of the process 9,10. We present a method of real-time imaging of signaling-complex formation during T-cell activation. Primary T-cells or T-cell lines, such as Jurkat, are transfected with plasmids encoding for proteins of interest fused to monomeric fluorescent proteins, preventing non-physiological oligomerization 11. Live T cells are dropped over a coverslip pre-coated with T-cell activating antibody 8,9, which binds to the CD3/TCR complex, inducing T-cell activation while overcoming the need for specific activating antigens. Activated cells are constantly imaged with the use of confocal microscopy. Imaging data are analyzed to yield quantitative results, such as the colocalization coefficient of the signaling proteins.

We describe a live-cell imaging method that provides insight into protein dynamics during the T-cell activation process. We demonstrate the combined usage of the T-cell spreading assay, confocal microscopy and imaging analysis to yield quantitative results to follow signaling complex formation throughout T-cell activation.

Protection against infectious diseases is mediated by the immune system 1,2. T lymphocytes are the master coordinators of the immune system, regulating ...

Real-time Imaging of Endothelial Cell-cell Junctions During Neutrophil Transmigration Under Physiological Flow

During inflammation, leukocytes leave the circulation and cross the endothelium to fight invading pathogens in underlying tissues. This process is known as leukocyte transendothelial migration. Two routes for leukocytes to cross the endothelial monolayer have been described: the paracellular route, i.e., through the cell-cell junctions and the transcellular route, i.e., through the endothelial cell body. However, it has been technically difficult to discriminate between the para- and transcellular route. We developed a simple in vitro assay to study the distribution of endogenous VE-cadherin and PECAM-1 during neutrophil transendothelial migration under physiological flow conditions. Prior to neutrophil perfusion, endothelial cells were briefly treated with fluorescently-labeled antibodies against VE-cadherin and PECAM-1. These antibodies did not interfere with the function of both proteins, as was determined by electrical cell-substrate impedance sensing and FRAP measurements. Using this assay, we were able to follow the distribution of endogenous VE-cadherin and PECAM-1 during transendothelial migration under flow conditions and discriminate between the para- and transcellular migration routes of the leukocytes across the endothelium.

Leukocytes cross the endothelial monolayer using the paracellular or the transcellular route. We developed a simple assay to follow the distribution of endogenous junctional VE-cadherin and PECAM-1 during leukocyte transendothelial migration under physiological flow to discriminate between the two transmigration routes.

During inflammation, leukocytes leave the circulation and cross the endothelium to fight invading pathogens in underlying tissues. This process is known ...

Imaging Neutrophils and Monocytes in Mesenteric Veins by Intravital Microscopy on Anaesthetized Mice in Real Time

Efficient immune response is dependent on rapid mobilization of blood leukocytes to the site of infection or injury. Investigating leukocyte migration in vivo is crucial for understanding the molecular basis of leukocyte transendothelial migration and interaction with vascular endothelium. One powerful approach involves intravital microscopy on transgenic mice expressing fluorescent proteins in cells of interest.
Here we present a protocol for imaging monocytes and neutrophils in the CX3CR1gfp/wt mouse i.v. injected with orange dye-labeled neutrophils with an inverted confocal microscope. Time-lapse movies gathered from 30 min&#160;to several hours of imaging allow the analysis of leukocyte behavior in mesenteric veins under both steady state and inflammatory conditions. We also describe the steps to locally induce blood vessel inflammation with TLR2/TLR1 agonist Pam3SK4 and monitor the subsequent recruitment of neutrophils and monocytes.
The presented technique can also be used to monitor other populations of leukocytes and investigate molecules implicated in leukocyte recruitment or trafficking using other stimuli or transgenic mice.

We detail a protocol to monitor the behavior of neutrophils and monocytes in mesenteric veins under steady state and inflammatory conditions using intravital confocal microscopy on anaesthetized mice.

Efficient immune response is dependent on rapid mobilization of blood leukocytes to the site of infection or injury. Investigating leukocyte migration in ...

Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the development and persistence of many health related infections. One of the most well described and studied biofilms in human disease occurs in chronic pulmonary infection of cystic fibrosis patients. When studying biofilms in the context of the host, many factors can impact biofilm formation and development. In order to identify how host factors may affect biofilm formation and development, we used a static chambered coverglass method to grow biofilms in the presence of host-derived factors in the form of sputum supernatants. Bacteria are seeded into chambers and exposed to sputum filtrates. Following 48 hr of growth, biofilms are stained with a commercial biofilm viability kit prior to confocal microscopy and analysis. Following image acquisition, biofilm properties can be assessed using different software platforms. This method allows us to visualize key properties of biofilm growth in presence of different substances including antibiotics.

This protocol describes the visualization of biofilm development following exposure to host-factors using a slide chamber model. This model allows for direct visualization of biofilm development as well as analysis of biofilm parameters using computer software programs.

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the ...

Qualitative and Quantitative Analysis of the Immune Synapse in the Human System Using Imaging Flow Cytometry

The immune synapse is the area of communication between T cells and antigen-presenting cells (APCs). T cells polarize surface receptors and proteins towards the immune synapse to assure a stable binding and signal exchange. Classical confocal, TIRF, or super-resolution microscopy have been used to study the immune synapse. Since these methods require manual image acquisition and time-consuming quantification, the imaging of rare events is challenging. Here, we describe a workflow that enables the morphological analysis of tens of thousands of cells. Immune synapses are induced between primary human T cells in pan-leukocyte preparations and Staphylococcus aureus enterotoxin B (SEB)-loaded Raji cells as APCs. Image acquisition is performed with imaging flow cytometry, also called In-Flow microscopy, which combines features of a flow cytometer and a fluorescence microscope. A complete gating strategy for identifying T cell/APC couples and analyzing the immune synapses is provided. As this workflow allows the analysis of immune synapses in unpurified pan-leukocyte preparations and hence requires only a small volume of blood (i.e., 1 mL), it can be applied to samples from patients. Importantly, several samples can be prepared, measured, and analyzed in parallel.

Here, we describe a complete workflow for the qualitative and quantitative analysis of immune synapses between primary human T cells and antigen-presenting cells. The method is based on imaging flow cytometry, which allows the acquisition and evaluation of several thousand cell images within a relatively short period of time.

The immune synapse is the area of communication between T cells and antigen-presenting cells (APCs). T cells polarize surface receptors and proteins ...