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>

The authors have nothing to disclose.

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.

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Immunology and Infection

5.4K Views.  University at Buffalo. Questo metodo può aiutare a rispondere a domande chiave nel campo della microbiologia, come il modo in cui il flusso di fluido altera la crescita e lo sviluppo del biofilm fungino. Il principale vantaggio di questa tecnica è che ci permette di valutare quantitativamente gli effetti del flusso sulla crescita e lo sviluppo del biofilm in tempo reale. Iniziate questo esperimento con l'assemblaggio dell'apparato di flusso, come descritto nel protocollo di testo.Il giorno dell'esperimento...