This research was carried out as part of Projects TIN2015-68454-R and 20961/PI/18, financed by the Spanish Ministry of Economy and Competitiveness and the S&#233;neca Foundation of the Murcia Region. Irene Hern&#225;ndez Mart&#237;nez and Francisco Javier Ib&#225;&#241;ez L&#243;pez from the Statistical Support Section of the Scientific and Research Area of Murcia University (Secci&#243;n de Apoyo Estad&#237;stico (SAE), &#193;rea Cient&#237;fica y de Investigaci&#243;n (ACTI), Universidad de Murcia, (Figure 1 were drawn by using pictures from Servier Medical Art. Servier Medical Art by Servier is licensed with a Creative Commons Attribution 3.0 Unported License (https://creativecommons.org/licenses/by/3.0/)

The algal species Chroothece mobilis was used for the present study. The species was obtained from the Microalgae Edaphic SE Spain, MAESE 20.29 culture collection. An overview of the protocol is shown in Figure 1.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64533/64533fig01.jpg" /> 
Figure 1: Overview of the study. Chroothece mobilis is incubated under extreme habitat conditions, such as different monochromatic lights, for 2 weeks. The effect on Chroothece&#39;s physiology is evaluated by autofluorescence of the proteins contained in phycobilisome and photosystems using a confocal laser scanning microscope. <a href="https://www.jove.com/files/ftp_upload/64533/64533fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
1. Sample preparation
<ol>
	<li>Prepare the inoculum of Chroothece mobilis from the agar culture of the collection by transferring it to the SWES liquid medium (Table 2). 
	NOTE: SWES &#34;Seewasser + Erddekokt + Salze&#34; = seawater medium23.</li>
	<li>Maintain all the cultures for 2 weeks with a 16:8 light/dark photoperiod at 20 &#176;C under low white light intensity (LL: 80 &#181;M/m2/s) conditions and without shaking, until the desired cell density is obtained (see step 1.3). 
	NOTE: The growth light conditions are 80 &#181;M/m2/s light intensity (active photosynthetic radiation, PAR). These conditions are used as the low light conditions (control). The composition of the SWES medium is provided in Table 2.</li>
	<li>Carry out inoculations for the different experiments in the exponential culture phase with a cell density of 5 x 103 cells/mL in a 24-well plate, using 1 mL per well. 
	NOTE: Perform cell counting with a Neubauer chamber24, and dilute the culture with SWES whenever necessary.</li>
</ol>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td colspan="2">SWES medium composition</td>
		</tr>
		<tr>
			<td>Component</td>
			<td>Concentration</td>
		</tr>
		<tr>
			<td>KNO3</td>
			<td>1.98 mM</td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>115 &#181;M</td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>81 &#181;M</td>
		</tr>
		<tr>
			<td>ZnSO4, 7H2O</td>
			<td>17 nM</td>
		</tr>
		<tr>
			<td>MnSO4, 7H2O</td>
			<td>45 Nm</td>
		</tr>
		<tr>
			<td>H3BO3, 4H2O</td>
			<td>3.1 mM</td>
		</tr>
		<tr>
			<td>Co(NO3)2</td>
			<td>17 mM</td>
		</tr>
		<tr>
			<td>Na2MoO4, 6H2O</td>
			<td>21 nM</td>
		</tr>
		<tr>
			<td>CuSO4, 2H2O</td>
			<td>0.1 nM</td>
		</tr>
		<tr>
			<td>FeSO4, 5H2O</td>
			<td>13 &#181;M</td>
		</tr>
		<tr>
			<td>EDTA, 7H2O</td>
			<td>11 &#181;M</td>
		</tr>
		<tr>
			<td>Vit B12</td>
			<td>5 &#181;g</td>
		</tr>
		<tr>
			<td>Soil extract</td>
			<td>30 mL</td>
		</tr>
		<tr>
			<td>Filtered river water</td>
			<td>455 mL</td>
		</tr>
	</tbody>
</table>
Table 2: SWES medium composition.
2. Reproducing extreme algae habitat conditions: green and red monochromatic light effect
<ol>
	<li>Add 1 mL of the cell culture from the stock culture prepared at the aforementioned cell density (step 1.2) to inoculate each well of a 24-well plate.</li>
	<li>Keep the cell culture covered for 2 weeks to reproduce the monochromatic light effect.
	<ol>
		<li>Use the green filter that allows green light to pass through from 470 to 570 nm with a peak at the 506 nm wavelength (according to the manufacturer&#39;s specifications; see Table of Materials) and expose it to the culture25.</li>
		<li>Use the red filter that allows red light between 590 and 720 nm and peaks at 678 nm (according to the manufacturer&#39;s specifications; see Table of Materials) to expose it to the culture25. 
		NOTE: The low white light intensity (LL: 80 &#181;M/m2/s; see Table of Materials) condition is used as the light intensity control to compare the obtained effects. The employed light intensity units are micromole per second and square meter (&#181;mol m-2 s-1) or photosynthetic photon flux density (PPFD).</li>
	</ol>
	</li>
</ol>
3. Autofluorescence imaging
NOTE: The setup of the imaging software (see Table of Materials) is illustrated in Figure 2.
<ol>
	<li>Turn on all the components of the inverted confocal laser scanning microscope (CLSM; see Table of materials), including the laser.</li>
	<li>Mount the cells from each experimental well of the 24-well plate in SWES growth medium to a 35 mm glass bottom dish (see Table of Materials) for imaging.</li>
	<li>Choose the 63x/1.30 NA glycerol immersion objective and place glycerol over the lens (see Table of Materials).</li>
	<li>Place the well plate on the microscope stage and ensure the specimen does not move during image acquisition.</li>
	<li>Center the specimen in the light path and focus on the center of the cell by selecting the plane with the highest fluorescence intensity.</li>
	<li>Open the image acquisition software and choose xy&#955; from the drop-down list in the acquisition mode26.</li>
	<li>Select the excitation line of the laser to 561 nm DPSS, 8 bits of dynamic range, and 1024 x 1024 pixels. 
	NOTE: Ensure the confocal microscope has a 561 nm DPSS laser or a white light laser (WLL).</li>
	<li>Collect the fluorescence emission spectra in the 10 nm bandwidth and the lambda step size of 4 nm within the 570-760 nm range.</li>
	<li>Set the pinhole at 1 Airy unit and run the lambda scan acquisition.</li>
	<li>Repeat this process as many times as possible in different fields of view to collect an acceptable amount of data for statistical analysis (usually a standard deviation lower than 10%22).</li>
	<li>Repeat the last step under the different conditions (under red and green lights) and save the data. 
	NOTE: Use the same acquisition settings for the different samples and conditions to compare and conduct the statistical analysis.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64533/64533fig02.jpg" /> 
Figure 2: Software setup. Imaging software user interface to set up the lambda scan parameters. (A) From left to right, to select the acquisition mode xy&#955; from the drop-down list, that corresponds to step 3.6 in the protocol, and to select the right immersion lens type, corresponding to step 3.3 in the protocol. Ensure to remove any filter from the light path in step 3.9. (B) The panel for setting up the lambda scan parameters corresponds to step 3.8 in the protocol. (C) Run the lambda scan in step 3.10. <a href="https://www.jove.com/files/ftp_upload/64533/64533fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Parameters to evaluate Chroothece&#39;s physiology
<ol>
	<li>Once the lambda scan is acquired, click on the quantify window at the top of the software (as shown in Figure 3) to evaluate the collected fluorescence emission spectra. Go to the Open project window and select one xy&#955; file (Figure 3).</li>
	<li>Select Stack profile analysis in the imaging software.</li>
	<li>Define a region of interest (ROI) of 4 &#181;m2 in the center of a cell to analyze the mean fluorescence intensity (MFI). Export the data in CSV format. 
	NOTE: It is important to avoid the presence of black pixels (to ensure the pixels selected contain positive values) and always maintain a same sized ROI.</li>
	<li>Repeat this process with different cells under different conditions to produce enough data to perform statistical analysis.</li>
	<li>Open the CSV files to select the different fluorescence emission peaks from the phycobiliproteins and chlorophylls of all the measured ROIs.
	<ol>
		<li>Select the fluorescence data of phycoerythrin-phycocyanobilin (PE-PCB; 620 nm), C-phycocyanin (CPC; 648 nm), allophycocyanin (APC; 660 nm), and chlorophyll a (Chl a; 680 nm), respectively, in the csv file.</li>
	</ol>
	</li>
	<li>Create a new table with all the maximum fluorescence values obtained from each phycobiliprotein and chlorophyll peak and plot the data on a graph.</li>
	<li>Perform statistical analysis.
	<ol>
		<li>Analyze if the obtained data meets normality and homoscedasticity27.</li>
		<li>Proceed to the t-test analysis27,28 if the first condition is true. If not, run a Mann-Whitney U test29.</li>
		<li>Consider the differences significant at p values &#60;0.05.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64533/64533fig03.jpg" /> 
Figure 3: Evaluating Chroothece&#39;s autofluorescence. To perform the autofluorescence analysis, ensure to select the quantify window and one xy&#955; file in the open projects window (step 4.1); select stack profile visualization (step 4.2); select a 4 &#181;m2 ROI in the center of a cell and click on the report button to export the lambda scan data in CSV format (step 4.3). <a href="https://www.jove.com/files/ftp_upload/64533/64533fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<ol>
	<li>Vis, M. L., Necchi, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Freshwater Red Algae: Phylogeny, Taxonomy and Biogeography. , (2021).</li><li>Aboal, M., 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=Diversity+of+Chroothece+(Rhodophyta,+Stylonematales)+including+two+new+species.">Diversity of Chroothece (Rhodophyta, Stylonematales) including two new species.</a> European Journal of Phycology. 53 (2), 189-197 (2018).</li><li>Millach, L., Obiol, A., Sol&#233;, A., Esteve, 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+method+to+analyse+in+vivo+the+physiological+state+and+cell+viability+of+phototrophic+microorganisms+by+confocal+laser+scanning+microscopy+using+a+dual+laser.">A novel method to analyse in vivo the physiological state and cell viability of phototrophic microorganisms by confocal laser scanning microscopy using a dual laser.</a> Journal of Microscopy. 268 (1), 53-65 (2017).</li><li>Millach, L., Villagrasa, E., Sol&#233;, A., Esteve, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+confocal+laser+scanning+microscopy+techniques+for+a+rapid+assessment+of+the+effect+and+cell+viability+of+Scenedesmus+sp.+DE2009+under+metal+stress.">Combined confocal laser scanning microscopy techniques for a rapid assessment of the effect and cell viability of Scenedesmus sp. DE2009 under metal stress.</a> Microscopy and Microanalysis. 25 (4), 998-1003 (2019).</li><li>Poryvkina, L., Babichenko, S., Leeben, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+phytoplankton+pigments+by+excitation+spectra+of+fluorescence.">Analysis of phytoplankton pigments by excitation spectra of fluorescence.</a> Proceedings of EARSeL-SIG-Workshop LIDAR. , (2000).</li><li>Beutler, M., 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=A+fluorometric+method+for+the+differentiation+of+algal+populations+in+vivo+and+in+situ.">A fluorometric method for the differentiation of algal populations in vivo and in situ.</a> Photosynthesis Research. 72 (1), 39-53 (2002).</li><li>Grigoryeva, N., Chistyakova, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+microscopic+spectroscopy+for+investigation+and+monitoring+of+biological+diversity+and+physiological+state+of+cyanobacterial+cultures.">Fluorescence microscopic spectroscopy for investigation and monitoring of biological diversity and physiological state of cyanobacterial cultures.</a> Cyanobacteria. , (2018).</li><li>Grigoryeva, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fluorescence Methods for Investigation of Living Cells and Microorganisms. , (2020).</li><li>Roshchina, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vital+autofluorescence:+application+to+the+study+of+plant+living+cells.">Vital autofluorescence: application to the study of plant living cells.</a> International Journal of Spectroscopy. 2012, 5-18 (2012).</li><li>Rold&#225;n, M., Thomas, F., Castel, S., Quesada, A., Hern&#225;ndez-Marin&#233;, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+pigment+identification+in+single+cells+from+living+phototrophic+biofilms+by+confocal+imaging+spectrofluorometry.">Noninvasive pigment identification in single cells from living phototrophic biofilms by confocal imaging spectrofluorometry.</a> Applied and Environmental Microbiology. 70 (6), 3745-3750 (2004).</li><li>Hense, B. A., Gais, P., J&#252;tting, U., Scherb, H., Rodenacker, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+fluorescence+information+for+automated+phytoplankton+investigation+by+image+analysis.">Use of fluorescence information for automated phytoplankton investigation by image analysis.</a> Journal of Plankton Research. 30 (5), 587-606 (2008).</li><li>Millie, D. F., Schofield, O. M., Kirkpatrick, G. J., Johnsen, G., Evens, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+absorbance+and+fluorescence+spectra+to+discriminate+microalgae.">Using absorbance and fluorescence spectra to discriminate microalgae.</a> European Journal of Phycology. 37 (3), 313-322 (2002).</li><li>Richardson, T. 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=Spectral+fluorometric+characterization+of+phytoplankton+community+composition+using+the+Algae+Online+Analyser.">Spectral fluorometric characterization of phytoplankton community composition using the Algae Online Analyser.</a> Water Research. 44 (8), 2461-2472 (2010).</li><li>Kieleck, C., Bousquet, B., Le Brun, G., Cariou, J., Lotrian, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+induced+fluorescence+imaging:+application+to+groups+of+macroalgae+identification.">Laser induced fluorescence imaging: application to groups of macroalgae identification.</a> Journal of Physics D: Applied Physics. 34 (16), 2561-2571 (2001).</li><li>Coronado-Parra, T., Rold&#225;n, M., Aboal, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confocal+microscopy+in+ecophysiological+studies+of+algae:+a+door+to+understanding+autofluorescence+in+red+algae.">Confocal microscopy in ecophysiological studies of algae: a door to understanding autofluorescence in red algae.</a> Microscopy and Microanalysis. 28 (1), 218-226 (2022).</li><li>Mulec, J., Kosi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lampenflora+algae+and+methods+of+growth+control.">Lampenflora algae and methods of growth control.</a> Journal of Cave and Karst Studies. 71 (2), 109-115 (2009).</li><li>Nelissen, B., De Baere, R., Wilmotte, A., De Wachter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phylogenetic+relationships+of+nonaxenic+filamentous+cyanobacterial+strains+based+on+16S+rRNA+sequence+analysis.">Phylogenetic relationships of nonaxenic filamentous cyanobacterial strains based on 16S rRNA sequence analysis.</a> Journal of Molecular Evolution. 42 (2), 194-200 (1996).</li><li>Rold&#225;n, M., Oliva, F., G&#243;nzalez Del Valle, M. A., Saiz-Jimenez, C., Hern&#225;ndez-Marin&#233;, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Does+green+light+influence+the+fluorescence+properties+and+structure+of+phototrophic+biofilms.">Does green light influence the fluorescence properties and structure of phototrophic biofilms.</a> Applied and Environmental Microbiology. 72 (4), 3026-3031 (2006).</li><li>Topinka, J. A., Bellows, W. K., Yentsch, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+marine+macroalgae+by+fluorescence+signatures.">Characterization of marine macroalgae by fluorescence signatures.</a> International Journal of Remote Sensing. 11 (12), 2329-2335 (1990).</li><li>Rold&#225;n, M., Ascaso, C., Wierzchos, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+fingerprints+of+endolithic+phototrophic+cyanobacteria+living+within+halite+rocks+in+the+atacama+desert.">Fluorescent fingerprints of endolithic phototrophic cyanobacteria living within halite rocks in the atacama desert.</a> Applied and Environmental Microbiology. 80 (10), 2998-3006 (2014).</li><li>Sol&#233;, A., Diestra, E., Esteve, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confocal+laser+scanning+microscopy+image+analysis+for+cyanobacterial+biomass+determined+at+microscale+level+in+different+microbial+mats.">Confocal laser scanning microscopy image analysis for cyanobacterial biomass determined at microscale level in different microbial mats.</a> Microbial Ecology. 57 (4), 649-656 (2009).</li><li>Ram&#237;rez, O., Garc&#237;a, A., Rojas, R., Couve, A., H&#228;rtel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confined+displacement+algorithm+determines+true+and+random+colocalization+in+fluorescence+microscopy.">Confined displacement algorithm determines true and random colocalization in fluorescence microscopy.</a> Journal of Microscopy. 239 (3), 173-183 (2010).</li><li>Universität Gottingen-Georg-August. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SAG+Culture+Collection+of+Algae.">SAG Culture Collection of Algae.</a> Universität Gottingen-Georg-August. , (2022).</li><li>Zhang, M., 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=Improvement+of+cell+counting+method+for+Neubauer+counting+chamber.">Improvement of cell counting method for Neubauer counting chamber.</a> Journal of Clinical Laboratory Analysis. 34 (1), 23024 (2020).</li><li>Wolf, E., Sch&#252;&#223;ler, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phycobiliprotein+fluorescence+of+Nostoc+punctiforme+changes+during+the+life+cycle+and+chromatic+adaptation:+Characterization+by+spectral+confocal+laser+scanning+microscopy+and+spectral+unmixing.">Phycobiliprotein fluorescence of Nostoc punctiforme changes during the life cycle and chromatic adaptation: Characterization by spectral confocal laser scanning microscopy and spectral unmixing.</a> Plant, Cell and Environment. 28 (4), 480-491 (2005).</li><li>Zucker, R. M., Rigby, P., Clements, I., Salmon, W., Chua, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reliability+of+confocal+microscopy+spectral+imaging+systems:+Use+of+multispectral+beads.">Reliability of confocal microscopy spectral imaging systems: Use of multispectral beads.</a> Cytometry Part A. 71 (3), 174-189 (2007).</li><li>Field, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Discovering Statistics Using R. , (2013).</li><li>Linnet, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Limitations+of+the+paired+t-test+for+evaluation+of+method+comparison+data.">Limitations of the paired t-test for evaluation of method comparison data.</a> Clinical Chemistry. 45 (2), 314-315 (1999).</li><li>Rosner, B., Grove, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+Mann-Whitney+U-test+for+clustered+data.">Use of the Mann-Whitney U-test for clustered data.</a> Statistics in Medicine. 18 (11), 1387-1400 (1999).</li><li>Colin, 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=Imaging+the+living+plant+cell:+from+probes+to+quantification.">Imaging the living plant cell: from probes to quantification.</a> The Plant Cell. 34 (1), 247-272 (2022).</li><li>Borlinghaus, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+white+confical:+continuous+spectral+tuning+in+excitation+and+emission.">The white confical: continuous spectral tuning in excitation and emission.</a> Optical Fluorescence Microscopy. , (2011).</li></ol>

The authors have no conflicts of interest to declare.

Some unicellular or colonial red algae, such as Chroothece,&#160;grow slowly in vitro, but contain multiple autofluorescent compounds that can be analyzed by spectral analysis under a confocal microscope, where differences in pigment emission peaks can be detected. Spectral confocal fluorescence microscopy has allowed us to conduct in vivo studies to evaluate the adaptation or acclimation of photosynthetic organisms8,10,<sup ...

Red algae, such as the genus Chroothece, can grow in extreme habitats, where they frequently have to cope with marked environmental changes1. Floods and droughts are frequent in semi-arid regions where this genus can be found, and some species have been reported in creeks, cliffs, caves, or even thermal waters2. However, most of the time, biological variables, such as competition or grazing, relegate species to non-optimal conditions for their growth. As these organisms are often difficult to culture and either do not grow or grow very slowly under laboratory conditions, one major limitation is the available sample size. Therefore, it is very important to follow non-destructive methods or methods that involve minimal sample manipulation3,4.
The physiological skills needed to survive in these harsh environments can be monitored by following changes in their photosynthetic systems. Metabolic mechanisms, photosynthetic efficiency, and sensitivity to light or culture conditions can be revealed by pigment fluorescence emission profiles, due to accurate changes in their energy transfer or trapping5,6,7,8.
Autofluorescence of cellular compounds can be used as a marker for cytodiagnosis or as a natural indicator of cellular state or metabolism in response to external and internal signals through changes in emission9. It can also be used to discriminate taxonomically different groups of photosynthetic organisms10. Depending on the phylogenetic position of phototrophic microorganisms, one can find different in vivo fluorescence features. Therefore, a taxonomic identification based on the in vivo characteristics of phototrophic fluorescence (including fluorescence absorption and emission spectra) has been attempted on several occasions11,12. Because of the diversity in accessory pigments among phytoplankton taxa, differences in the wavelengths at which chlorophyll a (Chl a) fluorescence is stimulated, or differences in emission spectra, can be used to infer taxonomy13. The in vivo fluorescence excitation and emission spectra of these specimens rely not only on the phyla of algae, but also on photosystem adaptation14. The efficiency of energy transfer to Chl a, or the ratio of Chl a to accessory pigments, and the cellular pigment content are sensitive to growth conditions5.
Red algae, particularly Chroothece, have several accessory fluorescent pigments-phycobiliproteins and carotenoids; the former concentrate in phycobilisomes attached to the thylakoids of chloroplasts. Phycobiliproteins (phycocyanin, phycoerythrin, and allophycocyanin) can capture light at different wavelengths and transmit it to Chl a, which makes photosynthesis in very different light and culture conditions possible15. For instance, Chroothece species can grow inside caves or almost emerge in slightly saline calcareous streams2.
Monochromatic lights affect the growth and pigment composition of photosynthetic organisms, and have been studied to prevent or control the growth of photosynthetic organisms in caves. Mulec et al. showed that red enriched lighting promotes the growth of cyanobacteria, algae, and plants16. Previous studies have also reported that green light affects the pigment composition of cyanobacteria17, while others have revealed that green light prevents the growth of most photosynthetic organisms and some cyanobacteria exhibit a reduction in thylakoids and weaker mean fluorescence intensity18.
To understand the ability of Chroothece as a model organism to overcome harsh conditions, cultured cells have been exposed to increasing light intensities and monochromatic light (green or red)15, to see how it copes with the dim conditions of caves (where red light predominates). The protocol presented herein reproduces the effect of the abovementioned variables on Chroothece&#39;s phycobiliproteins at the cellular level using its own autofluorescence.
Nowadays, fluorescence is commonly used as a tool to study the physiological responses of vascular plants, microalgae, macroalgae, and cyanobacteria13,14,16. Spectral confocal fluorescence microscopy is a superb tool for in vivo studies to evaluate photosynthetic specimens&#39; physiology at the single-cell level10,17,18,19,20, by avoiding problems associated with the low growth rate in the laboratory and the difficulties with obtaining enough biomass for the associated extraction and biochemical methods8. Once cells are treated under different culture conditions for 2 weeks, the lambda scan profile can be measured in vivo. Although there are several publications in which different wavelengths of excitation by confocal imaging have been used3,4,10,17, most phycobiliproteins and Chl a can be detected using a 561 nm wavelength excitation line, and the detected emission ranges from 570 to 760 nm wavelength. These criteria have been based on an analysis previously performed10 with commercial pure pigments (Table 1) by confocal imaging and the obtained results in different algae species20,21,22.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="2">Pigments</td>
			<td rowspan="2">&#955;flmax (nm)</td>
			<td colspan="8">&#955; exc (nm)</td>
		</tr>
		<tr>
			<td>351</td>
			<td>364</td>
			<td>458</td>
			<td>476</td>
			<td>488</td>
			<td>514</td>
			<td>543</td>
			<td>633</td>
		</tr>
		<tr>
			<td>Chl a</td>
			<td>660.9-678.1</td>
			<td>43.4 &#177; 1.8</td>
			<td>11.2 &#177; 0.2</td>
			<td>1.8 &#177; 0.05</td>
			<td>2.0 &#177; 0.08</td>
			<td>12.2 &#177; 0.7</td>
			<td>6.0 &#177; 0.3</td>
			<td>4.2 &#177; 0.16</td>
			<td>80.7 &#177; 1.5</td>
		</tr>
		<tr>
			<td rowspan="2">R-PE</td>
			<td>569.2-583.3</td>
			<td>5.9 &#177; 0.6</td>
			<td>5.9 &#177; 0.16</td>
			<td>11.1 &#177; 0.04</td>
			<td>42.2 &#177; 0.3</td>
			<td>100.0 &#177; 0</td>
			<td>90.0 &#177; 0.3</td>
			<td>99.2 &#177; 0.08</td>
			<td>-</td>
		</tr>
		<tr>
			<td>652.1-668.6</td>
			<td>-</td>
			<td>-</td>
			<td>1.5 &#177; 0.01</td>
			<td>3.7 &#177; 0.04</td>
			<td>26.7 &#177; 0.5</td>
			<td>8.7 &#177; 0.16</td>
			<td>11.1 &#177; 0.16</td>
			<td>11.3 &#177; 0.2</td>
		</tr>
		<tr>
			<td>C-PC</td>
			<td>636.2-676.4</td>
			<td>2.3 &#177; 0.04</td>
			<td>1.0 &#177; 0.01</td>
			<td>0.6 &#177; 0.004</td>
			<td>0.7 &#177; 0.008</td>
			<td>2.0 &#177; 0.08</td>
			<td>2.0 &#177; 0.04</td>
			<td>3.3 &#177; 0.16</td>
			<td>33.6 &#177; 0.9</td>
		</tr>
		<tr>
			<td>APC-XL</td>
			<td>667.3-683.8</td>
			<td>15.1 &#177; 1.5</td>
			<td>9.6 &#177; 0.98</td>
			<td>1.0 &#177; 0.04</td>
			<td>1.2 &#177; 0.08</td>
			<td>5.9 &#177; 0.7</td>
			<td>4.1 &#177; 0.5</td>
			<td>23.2 &#177; 3.5</td>
			<td>91.4 &#177; 2.3</td>
		</tr>
	</tbody>
</table>
Table 1: The pure pigment information used to run the lambda scan analysis. This table shows emission peaks and shoulders/fluorescence band maxima of different fluorochromes/pigments by confocal imaging spectrophotometry for all the excitation wavelengths, and the percentage of light emission by pigments/fluorochromes. Values were calculated by the formula: = MFI*100/255. Each value is the mean &#177; SE (mean &#177; standard error from the mean). Pure pigments were used for calibrating the confocal scanning laser microscope as follows1,2,10. Chlorophyll a was obtained from Spinacia oleracea, R-phycoerythrin (R-PE) from Porphyra tenera, and C-phycocyanin (C-PE) from Spirulina sp. All the species were dissolved in filtered distilled water. Allophycocyanin-XL (APC-XL) was obtained from Mastigocladus laminosus, which was dissolved in ammonium sulfate (60%) and potassium phosphate (pH = 7) to achieve a concentration of 38 mM. The scans were performed with 400 &#181;L of each pigment solution (concentration of 1 mg/mL) using an 8-well covered-glass bottom chamber.
The study of a single excitation wavelength is quite a useful first approximation. In this case, however, it is necessary to elucidate the relative contribution of the different complexes in the fluorescence signal, which is recommended to perform a fluorescence ratio or spectrum analysis at several wavelengths, among other methods.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>&#181;-Dish 35 mm, high Glass Bottom</td>
			<td>Ibidi&#160;</td>
			<td>81158</td>
			<td>-</td>
		</tr>
		<tr>
			<td>24 black well plate</td>
			<td>Ibidi</td>
			<td>82406</td>
			<td>&#160;flat and clear bottom for high throughput microscopy</td>
		</tr>
		<tr>
			<td>Algae Incubator</td>
			<td>Panasonic</td>
			<td>MLR-352-PE</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal laser scanning microscope</td>
			<td>Leica Microsystems</td>
			<td>SP8 TCS</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Flask</td>
			<td>Fisher Scientific</td>
			<td>15380591</td>
			<td>Can be purchased in a local convenience store or online stores.</td>
		</tr>
		<tr>
			<td>green filter</td>
			<td>PNTA, LEE filters</td>
			<td>-</td>
			<td>Can be purchased in a local convenience store or online stores.</td>
		</tr>
		<tr>
			<td>HC PL APO 63X/1.30 GLYC CORR CS2</td>
			<td>Leica Microsystems</td>
			<td>506353</td>
			<td>Glycerol immersion lens</td>
		</tr>
		<tr>
			<td>Image acquisition software. LAS X</td>
			<td>Leica Microsystems</td>
			<td>SP8 TCS</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Light source</td>
			<td>Panasonic</td>
			<td>FL40SSENW/37MLR-352-PE</td>
			<td></td>
		</tr>
		<tr>
			<td>Quantum photoradiometer</td>
			<td>DeltaOhm&#160;</td>
			<td>DO 9721</td>
			<td>-</td>
		</tr>
		<tr>
			<td>R software</td>
			<td>R Core Team, 2020</td>
			<td>4.0.2.</td>
			<td>-</td>
		</tr>
		<tr>
			<td>red filter</td>
			<td>PNTA, LEE filters</td>
			<td>-</td>
			<td>Can be purchased in a local convenience store or online stores.</td>
		</tr>
		<tr>
			<td>SWES medium</td>
			<td>University of Murcia</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Type G Immersion liquid</td>
			<td>Leica Microsystems</td>
			<td>11513910</td>
			<td>Glycerol&#160;</td>
		</tr>
	</tbody>
</table>

autofluorescence imaging to evaluate red algae physiology

Red algae (Rhodophyta) contain phycobiliproteins and colonize habitats with dim light, however some (e.g., some Chroothece species) can also develop in full sunshine. Most rhodophytes are red, however some can appear bluish, depending on the proportion of blue and red biliproteins (phycocyanin and phycoerythrin). Different phycobiliproteins can capture light at diverse wavelengths and transmit it to chlorophyll a, which makes photosynthesis under very different light conditions possible. These pigments respond to habitat changes in light, and their autofluorescence can help to study biological processes. Using Chroothece mobilis as a model organism and the spectral lambda scan mode in a confocal microscope, the adaptation of photosynthetic pigments to different monochromatic lights was studied at the cellular level to guess the species' optimal growth conditions. The results showed that, even when the studied strain was isolated from a cave, it adapted to both dim and medium light intensities. The presented method is especially useful for studying photosynthetic organisms that do not grow or grow very slowly under laboratory conditions, which is usually the case for those living in extreme habitats.

Chlorophyll a generally absorbs blue and red wavelengths of visible light, whereas phycobiliproteins use green, yellow, and orange wavelengths7. The autofluorescence of these pigments makes the first approach to study phycobiliproteins and chlorophyll behavior under experimental and field conditions possible.
By comparing the obtained data and plotting on different graphs, significant changes in mean fluorescence intensity (MFI) can be distinguished (<strong class="xfig...

Watch this Scientific Journal Video about Autofluorescence Imaging to Evaluate Red Algae Physiology at JoVE.com

Autofluorescence Imaging to Evaluate Red Algae Physiology

The present protocol describes step-by-step autofluorescence imaging and evaluation of phycobiliprotein changes in red algae based on spectral analysis. This is a label-free and non-destructive method to evaluate cellular adaptation to extreme habitats, when only scarce material is available and cells grow slowly, or not at all, under laboratory conditions.

Red algae (Rhodophyta) contain phycobiliproteins and colonize habitats with dim light, however some (e.g., some Chroothece species) can also develop in ...

autofluorescence-imaging-to-evaluate-red-algae-physiology

Research

JoVE Journal

Biology

1.3K Views.  University of Murcia. The present protocol describes step-by-step autofluorescence imaging and evaluation of phycobiliprotein changes in red algae based on spectral analysis. This is a label-free and non-destructive method to evaluate cellular adaptation to extreme habitats, when only scarce material is available and cells grow slowly, or not at all, under laboratory conditions.

Video: Autofluorescence Imaging to Evaluate Red Algae Physiology

Imaging Exocytosis in Retinal Bipolar Cells with TIRF Microscopy

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective imaging of fluorescent molecules that are closest to a high refractive index substance such as glass1. In this article, we apply this technique to image exocytosis of synaptic vesicles in retinal bipolar cells isolated from the goldfish retina. These neurons are very suitable for this kind of study due to their large axon terminals. By simultaneously patch clamping the bipolar cells, it is possible to investigate the relationship between pre-synaptic voltage and synaptic release2,3. Synaptic vesicles inside the bipolar cell terminals are loaded with a fluorescent dye (FM 1-43&reg;) by co-puffing the dye and a ringer solution containing a high K+ concentration onto the synaptic terminals. This depolarizes the cells and stimulates endocytosis and consequent dye uptake into the glutamatergic vesicles. After washing the excess dye away for around 30 minutes, cells are ready for being patch clamped and imaged simultaneously with a 488 nm laser. The patch pipette solution contains a rhodamine-based peptide that binds selectively to the synaptic ribbon protein RIBEYE4, thereby labeling ribbons specifically when terminals are imaged with a 561 nm laser. This allows the precise localization of active zones and the separation of synaptic from extra-synaptic events.

In this video, we demonstrate how to label and visualize single synaptic vesicle exocytosis and trafficking in goldfish retinal bipolar cells using total internal reflectance fluorescence (TIRF) microscopy.

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective ...

Preparation of Developing and Adult Drosophila Brains and Retinae for Live Imaging

The Drosophila brain and visual system are widely utilized model systems to study neuronal development, function and degeneration. Here we show three preparations of the brain and visual system that cover the range from the developing eye disc-brain complex in the developing pupae to individual eye and brain dissection from adult flies. All protocols are optimized for the live culture of the preparations. However, we also present the conditions for fixed tissue immunohistochemistry where applicable. Finally, we show live imaging conditions for these preparations using conventional and resonant 4D confocal live imaging in a perfusion chamber. Together, these protocols provide a basis for live imaging on different time scales ranging from functional intracellular assays on the scale of minutes to developmental or degenerative processes on the scale of many hours.

Preparation of Developing and Adult Drosophila Brains and Retinae for Live Imaging

This protocol describes three Drosophila preparations: 1) adult brain dissection, 2) adult retina dissection and 3) developing eye disc- brain complexes dissection. Emphasis is laid on special preparation techniques and conditions for live imaging, although all preparations can be used for fixed tissue immunohistochemistry.

The Drosophila brain and visual system are widely utilized model systems to study neuronal development, function and degeneration. Here we show three ...

The Mouse Cremaster Muscle Preparation for Intravital Imaging of the Microcirculation

Throughout the body, the maintenance of homeostasis requires the constant supply of oxygen and nutrients concomitant with removal of metabolic by-products. This balance is achieved by the movement of blood through the microcirculation, which encompasses the smallest branches of the vascular supply throughout all tissues and organs. Arterioles branch from arteries to form networks that control the distribution and magnitude of oxygenated blood flowing into the multitude of capillaries intimately associated with parenchymal cells. Capillaries provide a large surface area for diffusional exchange between tissue cells and the blood supply. Venules collect capillary effluent and converge as they return deoxygenated blood towards the heart. To observe these processes in real time requires an experimental approach for visualizing and manipulating the living microcirculation.
The cremaster muscle of rats was first used as a model for studying inflammation using histology and electron microscopy post mortem1,2. 
The first in vivo report of the exposed intact rat cremaster muscle investigated microvascular responses to vasoactive drugs using reflected light3. However 
curvature of the muscle and lack of focused illumination limited the usefulness of this preparation. The major breakthrough entailed opening the muscle, 
detaching it from the testicle and spreading it radially as a flat sheet for transillumination under a compound microscope4. While shown to be a valuable 
preparation to study the physiology of the microcirculation in rats5 and hamsters6, the cremaster muscle in mice7 has proven particularly useful in dissecting 
cellular pathways involved in regulating microvascular function8-11 and real-time imaging of intercellular signaling12. 
The cremaster muscle is derived from the internal oblique and transverse abdominus muscles as the testes descend through the inguinal canal13. 
It serves to support (Greek: cremaster = suspender) and maintain temperature of the testes. As described here, the cremaster muscle is prepared as a thin flat sheet 
for outstanding optical resolution. With the mouse maintained at a stable body temperature and plane of anesthesia, surgical preparation involves freeing the muscle 
from surrounding tissue and the testes, spreading it onto transparent pedestal of silastic rubber and securing the edges with insect pins while irrigating it 
continuously with physiological salt solution. The present protocol utilizes transgenic mice expressing GCaMP2 in arteriolar endothelial cells. GCaMP2 is a 
genetically encoded fluorescent calcium indicator molecule12. Widefield imaging and an intensified charge-coupled device camera enable in vivo study of 
calcium signaling in the arteriolar endothelium.

A tissue preparation is described for visualization and experimental manipulation of the living microcirculation. In anesthetized male mice, the thin, highly vascularized cremaster muscle is prepared for intravital microscopy to study microvascular networks including arterioles, capillaries and venules. This preparation is readily adapted for rats and hamsters.

Throughout the body, the maintenance of homeostasis requires the constant supply of oxygen and nutrients concomitant with removal of metabolic ...

Fluorescence-based Measurement of Store-operated Calcium Entry in Live Cells: from Cultured Cancer Cell to Skeletal Muscle Fiber

Store operated Ca2+ entry (SOCE), earlier termed capacitative Ca2+ entry, is a tightly regulated mechanism for influx of extracellular Ca2+ into cells to replenish depleted endoplasmic reticulum (ER) or sarcoplasmic reticulum (SR) Ca2+ stores1,2. Since Ca2+ is a ubiquitous second messenger, it is not surprising to see that SOCE plays important roles in a variety of cellular processes, including proliferation, apoptosis, gene transcription and motility. Due to its wide occurrence in nearly all cell types, including epithelial cells and skeletal muscles, this pathway has received great interest3,4. However, the heterogeneity of SOCE characteristics in different cell types and the physiological function are still not clear5-7.
The functional channel properties of SOCE can be revealed by patch-clamp studies, whereas a large body of knowledge about this pathway has been gained by fluorescence-based intracellular Ca2+ measurements because of its convenience and feasibility for high-throughput screening. The objective of this report is to summarize a few fluorescence-based methods to measure the activation of SOCE in monolayer cells, suspended cells and muscle fibers5,8-10. The most commonly used of these fluorescence methods is to directly monitor the dynamics of intracellular Ca2+ using the ratio of F340nm and F380nm (510 nm for emission wavelength) of the ratiometric Ca2+ indicator Fura-2. To isolate the activity of unidirectional SOCE from intracellular Ca2+ release and Ca2+ extrusion, a Mn2+ quenching assay is frequently used. Mn2+ is known to be able to permeate into cells via SOCE while it is impervious to the surface membrane extrusion processes or to ER uptake by Ca2+ pumps due to its very high affinity with Fura-2. As a result, the quenching of Fura-2 fluorescence induced by the entry of extracellular Mn2+ into the cells represents a measurement of activity of SOCE9. Ratiometric measurement and the Mn+2 quenching assays can be performed on a cuvette-based spectrofluorometer in a cell population mode or in a microscope-based system to visualize single cells. The advantage of single cell measurements is that individual cells subjected to gene manipulations can be selected using GFP or RFP reporters, allowing studies in genetically modified or mutated cells. The spatiotemporal characteristics of SOCE in structurally specialized skeletal muscle can be achieved in skinned muscle fibers by simultaneously monitoring the fluorescence of two low affinity Ca2+ indicators targeted to specific compartments of the muscle fiber, such as Fluo-5N in the SR and Rhod-5N in the transverse tubules9,11,12.

The extent of store-operated Ca2+ entry (SOCE) can be monitored using fluorescent Ca2+ indicators. Mn2+ quenching of such indicators assays SOCE in cultured cells and skeletal muscle fibers. A technique allowing spatial and temporal resolution of SOCE by confocal imaging of mechanically skinned muscle fibers is also described.

Store operated Ca2+ entry (SOCE), earlier termed capacitative Ca2+ entry, is a tightly regulated mechanism for influx of extracellular Ca2+ into cells to ...

Giant Liposome Preparation for Imaging and Patch-Clamp Electrophysiology

The reconstitution of ion channels into chemically defined lipid membranes for electrophysiological recording has been a powerful technique to identify and explore the function of these important proteins. However, classical preparations, such as planar bilayers, limit the manipulations and experiments that can be performed on the reconstituted channel and its membrane environment. The more cell-like structure of giant liposomes permits traditional patch-clamp experiments without sacrificing control of the lipid environment.
Electroformation is an efficient mean to produce giant liposomes &gt;10 &mu;m in diameter which relies on the application of alternating voltage to a thin, ordered lipid film deposited on an electrode surface. However, since the classical protocol calls for the lipids to be deposited from organic solvents, it is not compatible with less robust membrane proteins like ion channels and must be modified. Recently, protocols have been developed to electroform giant liposomes from partially dehydrated small liposomes, which we have adapted to protein-containing liposomes in our laboratory.
We present here the background, equipment, techniques, and pitfalls of electroformation of giant liposomes from small liposome dispersions. We begin with the classic protocol, which should be mastered first before attempting the more challenging protocols that follow. We demonstrate the process of controlled partial dehydration of small liposomes using vapor equilibrium with saturated salt solutions. Finally, we demonstrate the process of electroformation itself. We will describe simple, inexpensive equipment that can be made in-house to produce high-quality liposomes, and describe visual inspection of the preparation at each stage to ensure the best results.

Reconstituting functional membrane proteins into giant liposomes of defined composition is a powerful approach when combined with patch-clamp electrophysiology. However, conventional giant liposome production may be incompatible with protein stability. We describe protocols for producing giant liposomes from pure lipids or small liposomes containing ion channels.

The reconstitution of ion channels into chemically defined lipid membranes for electrophysiological recording has been a powerful technique to identify ...

In Vitro Reconstitution of Light-harvesting Complexes of Plants and Green Algae

In plants and green algae, light is captured by the light-harvesting complexes (LHCs), a family of integral membrane proteins that coordinate chlorophylls and carotenoids. In vivo, these proteins are folded with pigments to form complexes which are inserted in the thylakoid membrane of the chloroplast. The high similarity in the chemical and physical properties of the members of the family, together with the fact that they can easily lose pigments during isolation, makes their purification in a native state challenging. An alternative approach to obtain homogeneous preparations of LHCs was developed by Plumley and Schmidt in 19871, who showed that it was possible to reconstitute these complexes in vitro starting from purified pigments and unfolded apoproteins, resulting in complexes with properties very similar to that of native complexes. This opened the way to the use of bacterial expressed recombinant proteins for in vitro reconstitution. The reconstitution method is powerful for various reasons: (1) pure preparations of individual complexes can be obtained, (2) pigment composition can be controlled to assess their contribution to structure and function, (3) recombinant proteins can be mutated to study the functional role of the individual residues (e.g., pigment binding sites) or protein domain (e.g., protein-protein interaction, folding). This method has been optimized in several laboratories and applied to most of the light-harvesting complexes. The protocol described here details the method of reconstituting light-harvesting complexes in vitro currently used in our laboratory, and examples describing applications of the method are provided.

In Vitro Reconstitution of Light-harvesting Complexes of Plants and Green Algae

This protocol details the reconstitution of light-harvesting complexes in vitro. These integral membrane proteins coordinate chlorophylls and carotenoids and are responsible for harvesting light in higher plants and green algae.

In plants and green algae, light is captured by the light-harvesting complexes (LHCs), a family of integral membrane proteins that coordinate chlorophylls ...

Physiology Lab Demonstration: Glomerular Filtration Rate in a Rat

Measurements of glomerular filtration rate (GFR), and the fractional excretion of sodium (Na) and potassium (K) are critical in assessing renal function in health and disease. GFR is measured as the steady state renal clearance of inulin which is filtered at the glomerulus, but not secreted or reabsorbed along the nephron. The fractional excretion of Na and K can be determined from the concentration of Na and K in plasma and urine. The renal clearance of inulin can be demonstrated in an anesthetized animal which has catheters in the femoral artery, femoral vein and bladder. The equipment and supplies used for this procedure are those commonly available in a research core facility, and thus makes this procedure a practical means for measuring renal function. The purpose of this video is to demonstrate the procedures required to perform a lab demonstration in which renal function is assessed before and after a diuretic drug. The presented technique can be utilized to assess renal function in rat models of renal disease.

The purpose of this protocol is to demonstrate the principles and techniques for measuring and calculating glomerular filtration rate, urine flow rate, and excretion of sodium and potassium in a rat. This demonstration can be used to provide students with an overall conceptual understanding of how to measure renal function.

Measurements of glomerular filtration rate (GFR), and the fractional excretion of sodium (Na) and potassium (K) are critical in assessing renal function ...

Imaging the Intracellular Trafficking of APP with Photoactivatable GFP

Beta-amyloid (A&#946;) is the major constituent of senile plaques found in the brains of Alzheimer&#8217;s disease patients. A&#946; is derived from the sequential cleavage of Amyloid Precursor Protein (APP) by &#946; and &#947;-secretases. Despite the importance of A&#946; to AD pathology, the subcellular localization of these cleavages is not well established. Work in our laboratory and others implicate the endosomal/lysosomal system in APP processing after internalization from the cell surface. However, the intracellular trafficking of APP is relatively understudied.
While cell-surface proteins are amendable to many labeling techniques, there are no simple methods for following the trafficking of membrane proteins from the Golgi. To this end, we created APP constructs that were tagged with photo-activatable GFP (paGFP) at the C-terminus. After synthesis, paGFP has low basal fluorescence, but it can be stimulated with 413 nm light to produce a strong, stable green fluorescence. By using the Golgi marker Galactosyl transferase coupled to Cyan Fluorescent Protein (GalT-CFP) as a target, we are able to accurately photoactivate APP in the trans-Golgi network. Photo-activated APP-paGFP can then be followed as it traffics to downstream compartments identified with fluorescently tagged compartment marker proteins for the early endosome (Rab5), the late endosome (Rab9) and the lysosome (LAMP1). Furthermore, using inhibitors to APP processing including chloroquine or the &#947;-secretase inhibitor L685, 458, we are able to perform pulse-chase experiments to examine the processing of APP in single cells.
We find that a large fraction of APP moves rapidly to the lysosome without appearing at the cell surface, and is then cleared from the lysosome by secretase-like cleavages. This technique demonstrates the utility of paGFP for following the trafficking and processing of intracellular proteins from the Golgi to downstream compartments.

While the transport of cell surface proteins is relatively easily studied, visualizing the trafficking of intracellular proteins is much more difficult. Here, we use constructs incorporating photoactivatable GFP and demonstrate a method to accurately follow the amyloid precursor protein from the Golgi apparatus to down-stream compartments and follow its clearance.

Beta-amyloid (A&#946;) is the major constituent of senile plaques found in the brains of Alzheimer&#8217;s disease patients. A&#946; is derived from the ...

Intracavernosal Pressure Recording to Evaluate Erectile Function in Rodents

Erectile dysfunction (ED) is defined as the inability to attain or keep an erection of the penis, and this has become a prevalent male sexual disorder. Rodents are employed by many studies to research the physiology/pathology of erectile function. Erectile function in rodents can be evaluated by measuring the intracavernosal pressure (ICP). In practice, ICP can be monitored following electrical stimulation of the cavernous nerves (CNs). The arterial pressure of the carotid artery (the mean arterial pressure) is used as the reference for ICP. Using ICP recording protocols, many key parameters of erectile function can be measured from the ICP response curve. The ICP measurement provides more information than the apomorphine-induced penile erection test, and is cheaper than telemetric monitoring of the corpus spongiosum penis, making this method the most popular one to evaluate erectile function. However, compared to the easily-performed APO-induced erectile function test, successful ICP recordings require attention to detail, practice, and adherence to the operation method. In this work, an introduction to ICP recording in rats is provided to complement the procedure efficiently.

Intracavernosal pressure recording (ICP) is an important method to evaluate the erectile function of experimental animals. Here, a detailed protocol is demonstrated for the recording procedure of ICP by catheterizing the crura penis and then electrically stimulating the cavernous nerves in rats.

Erectile dysfunction (ED) is defined as the inability to attain or keep an erection of the penis, and this has become a prevalent male sexual disorder. ...

Establishment of a Clonal Culture of Unicellular Conjugating Algae

It is essential to establish clonal cultures of microalgae for use in studies of various topics, such as physiology, genetics, taxonomy, and microbiology. Thus, it is extremely important to develop techniques to establish clonal cultures. In this article, we demonstrate the establishment of clonal cultures of a conjugating alga. Water samples are collected from the field. Subsequently, cells are isolated using a glass capillary pipette, placed in media, and grown under conditions suitable for generating a clonal culture.

In this article, we demonstrate the establishment of clonal cultures of unicellular conjugating algal species collected from a natural field site.

It is essential to establish clonal cultures of microalgae for use in studies of various topics, such as physiology, genetics, taxonomy, and microbiology. ...

Autofluorescence Imaging to Evaluate Red Algae Physiology

Summary

Explore More Videos

Chapters in this video

Imaging Exocytosis in Retinal Bipolar Cells with TIRF Microscopy

Preparation of Developing and Adult Drosophila Brains and Retinae for Live Imaging

The Mouse Cremaster Muscle Preparation for Intravital Imaging of the Microcirculation

Fluorescence-based Measurement of Store-operated Calcium Entry in Live Cells: from Cultured Cancer Cell to Skeletal Muscle Fiber

Giant Liposome Preparation for Imaging and Patch-Clamp Electrophysiology

In Vitro Reconstitution of Light-harvesting Complexes of Plants and Green Algae

Physiology Lab Demonstration: Glomerular Filtration Rate in a Rat

Imaging the Intracellular Trafficking of APP with Photoactivatable GFP

Intracavernosal Pressure Recording to Evaluate Erectile Function in Rodents

Establishment of a Clonal Culture of Unicellular Conjugating Algae