Name: photobleaching enables super-resolution imaging of the ftsz ring in the cyanobacterium prochlorococcus
Uploaded: 2018-11-06T15:00:00
Description: Watch this Scientific Journal Video about Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus at JoVE.com

The authors thank Daiying Xu for her technical assistance and comments on the manuscript. This study is supported by grants from the National Natural Science Foundation of China (Project number 41476147) and the Research Grants Council of the Hong Kong Special Administrative Region, China (project numbers 689813 and 16103414).

1. Sample Preparation and Fixation
<ol>
	<li>Inoculate 1 mL of axenic Prochlorococcus MED4 to 5 mL of the seawater-based Pro99 medium12. Grow Prochlorococcus cultures at 23 &#176;C under the light with an intensity of 35 &#181;mol photons/m2s. Five days later, collect 1 mL of culture into a 1.5-mL tube. 
	NOTE: Five days after the inoculation, Prochlorococcus MED4 will reach the late log phase, with approximately 108 cell/mL, which is appropr...

<ol>
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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+photobleaching+necessary+for+Raman+imaging+of+bone+tissue+using+a+green+laser?.">Is photobleaching necessary for Raman imaging of bone tissue using a green laser?.</a> Biochimica et Biophysica Acta. 1758 (7), 868-873 (2006).</li><li>Haxo, F. T., Blinks, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photosynthetic+Action+Spectra+of+Marine+Algae.">Photosynthetic Action Spectra of Marine Algae.</a> The Journal of General Physiology. 33 (4), 389-422 (1950).</li><li>Bryant, D. 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In this protocol, we described a procedure to significantly reduce the autofluorescence of the cyanobacterium Prochlorococcus (Figure 3C) and, then, immunostain the proteins in the cells, which enabled us to utilize STORM to study the 3-D FtsZ ring morphologies in Prochlorococcus (Figure 4). This protocol might be adopted for super-resolution imaging in other photosynthetic organisms.
Previous studies on photosynthet...

Super-resolution microscopies can break the diffraction limit of light and provide images within sub-diffraction resolutions (&#60; 200 nm). They have been widely used in many organisms to study protein localization and subcellular structures. Major super-resolution microscopy methods include structured illumination microscopy (SIM), stimulated emission depletion microscopy (STED), STORM, and photoactivated localization microscopy (PALM). The mechanisms and applications of these super-resolution microscopes have been reviewed elsewhere1,2.
STORM can achieve a resolution as high as 10 nm by spatial separation3,4. For STORM, only one molecule within a diffraction-limited region is activated (&#34;on&#34;) and the rest of the molecules are kept inactivated (&#34;off&#34;). By an accumulation of rapid switch-on and -off of single molecules, a &#34;diffraction-unlimited&#34; image can be generated3. Meanwhile, many kinds of organic dyes and fluorescent proteins are applicable in STORM, allowing an easy upgrade from regular fluorescence microscopy to high-resolution microscopy5,6.
STORM has not been widely applied in photosynthetic cells, such as cyanobacteria, algae, and plant cells with chloroplasts7,8, which is due to the fact that STORM requires high laser intensity to drive photoswitching. The high-intensity laser unfavorably excites strong autofluorescence background in photosynthetic cells and interferes with the single-molecule localization in STORM imaging. In order to use STORM to investigate the subcellular structures or protein interactions in photosynthetic cells, we developed a photobleaching protocol to quench the background autofluorescence signals9. In a routine immunofluorescent staining procedure, specimens are exposed to white light of a high intensity during the blocking step, which lowers the autofluorescence of photosynthetic cells to meet the requirements for STORM. Thus, this protocol makes it feasible to investigate pigmented organisms with STORM.
Here, we describe the protocol to use STORM to image the FtsZ ring organization in the unicellular picocyanobacterium Prochlorococcus. FtsZ is a highly conserved tubulin-like cytoskeletal protein which polymerizes to form a ring structure (the Z ring) around the circumference of a cell10 and is essential for the cell division11. Preserved Prochlorococcus cells are first photobleached to reduce the autofluorescent background and immunostained with a primary anti-FtsZ antibody, and then a secondary anti-Rabbit IgG (H+L) antibody is conjugated with a fluorophore (e.g., Alexa Fluor 750). Eventually, STORM is used to observe the detailed FtsZ ring organizations in Prochlorococcus during different cell cycle stages.

<table>
	<tbody>
		<tr>
			<td>Polystyrene particles</td>
			<td>Spherotech</td>
			<td>PP-20-10</td>
			<td>2.0-2.4 &#181;m</td>
		</tr>
		<tr>
			<td>Coverslip</td>
			<td>Marienfeld</td>
			<td>0111580</td>
			<td>18 mm &#8709;, Thickness No. 1</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Scharlau</td>
			<td>ET00021000</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-lysine hydrobromide</td>
			<td>Sigma-Aldrich</td>
			<td>P9155</td>
			<td>mol wt 70,000-150,000</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutaraldehyde solution, 50%</td>
			<td>Sigma-Aldrich</td>
			<td>340855</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma</td>
			<td>P3813</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA Disodium Salt, 2-hydrate</td>
			<td>Gold biotechnology</td>
			<td>E-210-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Sigma</td>
			<td>L6876</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat serum</td>
			<td>Sigma</td>
			<td>G9023</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Anabaena FtsZ antibody</td>
			<td>Agrisera</td>
			<td>AS07217</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Cross-Adsorbed Secondary Antibody</td>
			<td>Life Technologies</td>
			<td>A-21039</td>
			<td>conjugated with Alexa Fluor 750</td>
		</tr>
		<tr>
			<td>D-Glucose Anhydrous</td>
			<td>Fisher Scientific</td>
			<td>D16-1</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Ascorbic Acid</td>
			<td>Sigma-Aldrich</td>
			<td>A5960</td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl Viologen</td>
			<td>Sigma-Aldrich</td>
			<td>856177</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclooctatetraene</td>
			<td>Sigma-Aldrich</td>
			<td>138924</td>
			<td></td>
		</tr>
		<tr>
			<td>tris(2-carboxyethyl)phosphine (TCEP)</td>
			<td>Sigma-Aldrich</td>
			<td>646547</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose Oxidase</td>
			<td>Sigma-Aldrich</td>
			<td>G2133</td>
			<td></td>
		</tr>
		<tr>
			<td>Catalase</td>
			<td>Sigma-Aldrich</td>
			<td>C9322</td>
			<td></td>
		</tr>
		<tr>
			<td>XD-300 Xenon light source</td>
			<td></td>
			<td></td>
			<td>250 W</td>
		</tr>
		<tr>
			<td>STORM microscope</td>
			<td>NBI</td>
			<td>SRiS microscope</td>
			<td></td>
		</tr>
		<tr>
			<td>Rohdea</td>
			<td>NBI</td>
			<td>SRiS 3.0</td>
			<td>software for imaging acquisition</td>
		</tr>
		<tr>
			<td>Luna</td>
			<td>NBI</td>
			<td>SRiS 3.0</td>
			<td>software for drifting correction</td>
		</tr>
		<tr>
			<td>QuickPALM</td>
			<td></td>
			<td></td>
			<td>https://code.google.com/archive/p/quickpalm/wikis</td>
		</tr>
		<tr>
			<td>3D Viewer</td>
			<td></td>
			<td></td>
			<td>http://132.187.25.13/ij3d/?page=Home&#38;category=Home</td>
		</tr>
	</tbody>
</table>

photobleaching enables super-resolution imaging of the ftsz ring in the cyanobacterium prochlorococcus

Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, however, the lateral resolution of super-resolution imaging is only ~100 nm. The low resolution is mainly due to the high autofluorescence background of photosynthetic cells caused by high-intensity lasers that are required for super-resolution imaging, such as stochastic optical reconstruction microscopy (STORM). Here, we describe a photobleaching-assisted STORM method which was developed recently for imaging the marine picocyanobacterium Prochlorococcus. After photobleaching, the autofluorescence of Prochlorococcus is effectively reduced so that STORM can be performed with a lateral resolution of ~10 nm. Using this method, we acquire the in vivo three-dimensional (3-D) organization of the FtsZ protein and characterize four different FtsZ ring morphologies during the cell cycle of Prochlorococcus. The method we describe here might be adopted for the super-resolution imaging of other photosynthetic organisms.

STORM achieves super-resolution imaging by activating individual photoswitchable fluorophores stochastically. The location of every fluorophore is recorded and a super-resolution image is then constructed based on these locations4. Therefore, the precision of the fluorophore location is important for the super-resolution image reconstruction. The absorption spectra of Prochlorococcus peak at 447 nm and 680 nm,and Prochlorococcus has a minimum abso...

Watch this Scientific Journal Video about Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus at JoVE.com

Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus

Here we describe a photobleaching method to reduce the autofluorescence of cyanobacteria. After photobleaching, stochastic optical reconstruction microscopy is used to obtain three-dimensional super-resolution images of the cyanobacterial FtsZ ring.

Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus

Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, ...

This method can help answer key questions on protein localization and the dynamics in photosynthetic organisms. By combining the photobleaching method with super-resolution microscope, we are able to detect the protein dynamics of photosynthetic organisms in a remarkable detail. This method not only provides insight into the protein dynamics of Prochlorococcus.It can also be applied to many other organisms containing radio-re-dop-sing and bacteriochlorophyll. Demonstrating this procedure will be Yanxin Liu, a graduate student from my laboratory. To begin, add five milliliters of seawater-based Pro99 medium to a culture flask and inoculate it with one milliliter of Prochlorococcus MED4.Grow the Prochlorococcus at 23 degrees Celsius under a light with an intensity of 35 micromole photons per square meter. After five days, collect one milliliter of the culture into a 1.5 milliliter tube. Add 100 microliters of freshly prepared formaldehyde to the tube to fix the culture.Incubate in the dark at room temperature for 20 minutes. Then, spin down the sample at 13, 500 times G for one minute. Remove the supernatant and resuspend the cells in 100 microliters of Pro99 medium.Store the sample at four degrees Celsius in the dark until ready to perform immunostaining. First, vortex the vial of polystyrene beads. Using 50%ethanol, prepare a one-to-20, 000 dilution as a working slurry.Turn on the hotplate and set the temperature to 120 degrees Celsius. Next, place the coverslips onto the hot plate. Load 100 microliters of the working slurry onto each coverslip and incubate the coverslips on the hotplate for 10 minutes.Then carefully transfer the coverslips to Petri dishes bead-side up for storage at room temperature. When ready to coat the coverslips, retrieve one, making sure that it is bead-side up. Add 100 microliters of a one milligram per milliliter poly-L-lysine solution to the center of the coverslip and let it sit at room temperature for 30 minutes.After this, use a pipette to carefully aspirate any unattached poly-L-lysine and transfer it to a 1.5 milliliter tube. Store this poly-L-lysine at four degrees Celsius for later use. Rinse the coverslip with 10 milliliters of ultra filtered water in a 60-millimeter Petri dish and then briefly dry it with a paper towel.Transfer the coated coverslip to a new Petri dish with Parafilm at the bottom, which will be used as the staining dish. Load 100 microliters of the fixed sample onto the coverslip and let it sit for 30 minutes to allow cell attachment. Next, use a paper towel to absorb the remaining solution and then transfer the coverslip to a well in a 12-well plate for washing.Add one milliliter of PBS buffer to the well to wash the coverslip. Then remove the PBS and add one milliliter of fresh PBS to wash the coverslip a second time. Use a pipette to remove the PBS and replace it with one milliliter of freshly prepared permeabilization buffer.Incubate the washing dish at 37 degrees Celsius for 20 minutes. Then remove the permeabilization buffer. Begin the washing process by adding one milliliter of fresh PBS buffer.Place the washing dish on a shaker to gently agitate the dish for five minutes. After this, remove the PBS and repeat the washing process three times. Transfer the washed coverslip to the staining dish.Add 50 microliters of blocking buffer on the top of the coverslip. Place the entire staining dish on ice and then move it under the xenon light source for photobleaching for at least 60 minutes. After photobleaching and blocking, use the edge of a paper towel to remove the blocking buffer.First, dilute one microliter of anti-FtsZ antibody into 99 microliters of blocking buffer. Place 50 microliters of the diluted primary antibody onto the coverslip and incubate it at room temperature for 30 minutes. Transfer the coverslip to a well of the washing dish.To begin the wash, add one milliliter of PBS. Then transfer the washing dish to a shaker and gently shake it for five minutes. Remove the PBS and repeat the entire washing process three times.Next, transfer the coverslip to the staining dish. Place 50 microliters of the diluted secondary antibody onto the coverslip and incubate it in the dark and at room temperature for 30 minutes. Transfer the coverslip back to the washing dish.To begin the wash, add one milliliter of PBS. Wrap the washing dish in aluminum foil to protect it from light. Transfer the plate to the shaker and gently shake it for five minutes.Remove the PBS and repeat the entire washing process three times. Immediately before the STORM imaging, prepare one milliliter of imaging buffer as outlined in the text protocol. Load the coverslip into the loading chamber.Add the freshly prepared imaging buffer, being gentle to avoid washing off the cyanobacterial cells. After this, place a rectangular coverslip on top of the imaging buffer to prevent it from reacting with the oxygen in the air. Turn on the camera, the LED light, and the laser, and open the STORM software.Add half a drop of immersion oil on top of the lens. Load the chamber, making sure that the objective lens is making contact with the coverslip. And examine the signal with a 750-nanometer laser.Identify a sample area that contains both cells and fiducial markers. Then start the software for sample drifting correction. Acquire one wide-filed images as a reference, with the camera electron multiplication gain at 300 and an exposure time of 30 milliseconds.Increase the 750-nanometer excitation laser intensity to approximately 4.5 kilowatts per square centimeter. Once the fluorophores have transitioned into a sparse blinking pattern, acquire one super-resolution image by collecting 10, 000 frames at 33 hertz. Then reconstruct the super-resolution images from the raw data as outlined in the text protocol.In this study, STORM is used to achieve super-resolution imaging by activating individual photo-switchable fluorophores stochastically. The location of every fluorophore is recorded, and a super-resolution image is then constructed based on these locations. While the absorption spectra of Prochlorococcus peaks at 447 and 680 nanometers and has minimum absorption above 700 nanometers, Prochlorococcus MED4 cells still emit high autofluorescence when exposed to an extremely high intensity of the 750-nanometer laser, which is required for STORM imaging.After using the photobleaching method described here for 30 minutes, the cells'autofluorescence is seen to decrease, although several cells with autofluorescence are still detected. Elongating the photobleaching to 60 minutes results in the majority of the cells losing their autofluorescence. These results indicate that the developed photobleaching method is capable of greatly reducing the autofluorescence of photosynthetic organisms.After photobleaching, STORM is used to visualize the cell division protein, FtsZ, in the cells. Using STORM, a detailed morphology of the FtsZ ring is revealed. By rotating the 3D STORM images, four different types of morphologies were identified, clusters, an incomplete ring, a complete ring, and double rings.It is important to remember that the light intensity and duration of the photobleach may differ for different organisms. After its development, this method paves the way for researchers who want to study protein organization and potential function in photosynthetic cells in detail.

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JoVE Journal

Immunology and Infection

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most common forms of disease are visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). Mouse models of leishmaniasis are widely used, but quantification of parasite burdens during murine disease requires mice to be euthanized at various times after infection. Parasite loads are then measured either by microscopy, limiting dilution assay, or qPCR amplification of parasite DNA. The in vivo imaging system (IVIS) has an integrated software package that allows the detection of a bioluminescent signal associated with cells in living organisms. Both to minimize animal usage and to follow infection longitudinally in individuals, in vivo models for imaging Leishmania spp. causing VL or CL were established. Parasites were engineered to express luciferase, and these were introduced into mice either intradermally or intravenously. Quantitative measurements of the luciferase driving bioluminescence of the transgenic Leishmania parasites within the mouse were made using IVIS. Individual mice can be imaged multiple times during longitudinal studies, allowing us to assess the inter-animal variation in the initial experimental parasite inocula, and to assess the multiplication of parasites in mouse tissues. Parasites are detected with high sensitivity in cutaneous locations. Although it is very likely that the signal (photons/second/parasite) is lower in deeper visceral organs than the skin, but quantitative comparisons of signals in superficial versus deep sites have not been done. It is possible that parasite numbers between body sites cannot be directly compared, although parasite loads in the same tissues can be compared between mice. Examples of one visceralizing species (L. infantum chagasi) and one species causing cutaneous leishmaniasis (L. mexicana) are shown. The IVIS procedure can be used for monitoring and analyzing small animal models of a wide variety of Leishmania species causing the different forms of human leishmaniasis.

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

An in vivo imaging system is used to generate quantitative measurements of murine infection with the Trypanosomatid protozoan Leishmania. This is a non-invasive and non-lethal method for detecting parasites expressing luciferase within many tissues throughout the course of chronic Leishmania spp. infection.

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most ...

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

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 ...

Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging

Continuous advancements in noninvasive imaging modalities such as magnetic resonance imaging (MRI) have greatly improved our ability to study physiological or pathological processes in living organisms. MRI is also proving to be a valuable tool for capturing transplanted cells in vivo. Initial cell labeling strategies for MRI made use of contrast agents that influence the MR relaxation times (T1, T2, T2*) and lead to an enhancement (T1) or depletion (T2*) of signal where labeled cells are present. T2* enhancement agents such as ultrasmall iron oxide agents (USPIO) have been employed to study cell migration and some have also been approved by the FDA for clinical application. A drawback of T2* agents is the difficulty to distinguish the signal extinction created by the labeled cells from other artifacts such as blood clots, micro bleeds or air bubbles. In this article, we describe an emerging technique for tracking cells in vivo that is based on labeling the cells with fluorine (19F)-rich particles. These particles are prepared by emulsifying perfluorocarbon (PFC) compounds and then used to label cells, which subsequently can be imaged by 19F MRI. Important advantages of PFCs for cell tracking in vivo include (i) the absence of carbon-bound 19F in vivo, which then yields background-free images and complete cell selectivityand(ii) the possibility to quantify the cell signal by 19F MR spectroscopy.

Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging

Tracking of cells using MRI has gained remarkable attention in the past years. This protocol describes the labeling of dendritic cells with fluorine (19F)-rich particles, the in vivo application of these cells, and monitoring the extent of their migration to the draining lymph node with 19F/1H MRI and 19F MRS.

Continuous  advancements in noninvasive imaging modalities such as magnetic resonance  imaging (MRI) have greatly improved our ability to study ...

Super-resolution Imaging of the Natural Killer Cell Immunological Synapse on a Glass-supported Planar Lipid Bilayer

The glass-supported planar lipid bilayer system has been utilized in a variety of disciplines. One of the most useful applications of this technique has been in the study of immunological synapse formation, due to the ability of the glass-supported planar lipid bilayers to mimic the surface of a target cell while forming a horizontal interface. The recent advances in super-resolution imaging have further allowed scientists to better view the fine details of synapse structure. In this study, one of these advanced techniques, stimulated emission depletion (STED), is utilized to study the structure of natural killer (NK) cell synapses on the supported lipid bilayer. Provided herein is an easy-to-follow protocol detailing: how to prepare raw synthetic phospholipids for use in synthesizing glass-supported bilayers; how to determine how densely protein of a given concentration occupies the bilayer's attachment sites; how to construct a supported lipid bilayer containing antibodies against NK cell activating receptor CD16; and finally, how to image human NK cells on this bilayer using STED super-resolution microscopy, with a focus on distribution of perforin positive lytic granules and filamentous actin at NK synapses. Thus, combining the glass-supported planar lipid bilayer system with STED technique, we demonstrate the feasibility and application of this combined technique, as well as intracellular structures at NK immunological synapse with super-resolution.

We describe here a combination of the glass-supported lipid bilayer technique of forming immunological synapses with the super-resolution imaging technique of stimulated emission depletion (STED) microscopy. The goal of this protocol is to provide users with the instructions necessary to successfully carry out these two techniques.

The glass-supported planar lipid bilayer system has been utilized in a variety of disciplines. One of the most useful applications of this technique has ...

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 ...

Highly Multiplexed, Super-resolution Imaging of T Cells Using madSTORM

Imaging heterogeneous cellular structures using single molecule localization microscopy has been hindered by inadequate localization precision and multiplexing ability. Using fluorescent nano-diamond fiducial markers, we describe the drift correction and alignment procedures required to obtain high precision in single molecule localization microscopy. In addition, a new multiplexing strategy, madSTORM, is described in which multiple molecules are targeted in the same cell using sequential binding and elution of fluorescent antibodies. madSTORM is demonstrated on an activated T cell to visualize the locations of different components within a membrane-bound, multi-protein structure called the T cell receptor microcluster. In addition, application of madSTORM as a general tool for visualization of multi-protein structures is discussed.

We demonstrate a method to image multiple molecules within heterogeneous nano-structures at single molecule accuracy using sequential binding and elution of fluorescently labeled antibodies.

Imaging heterogeneous cellular structures using single molecule localization microscopy has been hindered by inadequate localization precision and ...

High-throughput Measurement of Plasma Membrane Resealing Efficiency in Mammalian Cells

In their physiological environment, mammalian cells are often subjected to mechanical and biochemical stresses that result in plasma membrane damage. In response to these damages, complex molecular machineries rapidly reseal the plasma membrane to restore its barrier function and maintain cell survival. Despite 60 years of research in this field, we still lack a thorough understanding of the cell resealing machinery. With the goal of identifying cellular components that control plasma membrane resealing or drugs that can improve resealing, we have developed a fluorescence-based high-throughput assay that measures the plasma membrane resealing efficiency in mammalian cells cultured in microplates. As a model system for plasma membrane damage, cells are exposed to the bacterial pore-forming toxin listeriolysin O (LLO), which forms large 30-50 nm diameter proteinaceous pores in cholesterol-containing membranes. The use of a temperature-controlled multi-mode microplate reader allows for rapid and sensitive spectrofluorometric measurements in combination with brightfield and fluorescence microscopy imaging of living cells. Kinetic analysis of the fluorescence intensity emitted by a membrane impermeant nucleic acid-binding fluorochrome reflects the extent of membrane wounding and resealing at the cell population level, allowing for the calculation of the cell resealing efficiency. Fluorescence microscopy imaging allows for the enumeration of cells, which constitutively express a fluorescent chimera of the nuclear protein histone 2B, in each well of the microplate to account for potential variations in their number and allows for eventual identification of distinct cell populations. This high-throughput assay is a powerful tool expected to expand our understanding of membrane repair mechanisms via screening for host genes or exogenously added compounds that control plasma membrane resealing.

Here we describe a high-throughput fluorescence-based assay that measures the plasma membrane resealing efficiency through fluorometric and imaging analyses in living cells. This assay can be used for screening drugs or target genes that regulate plasma membrane resealing in mammalian cells.

In their physiological environment, mammalian cells are often subjected to mechanical and biochemical stresses that result in plasma membrane damage. In ...

Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a striking increase in life expectancy around the globe. Nonetheless, determining vaccine efficacy remains a challenge. Emerging evidence suggests that the current acellular vaccine (aPV) for Bordetella pertussis (B. pertussis) induces suboptimal immunity. Therefore, a major challenge is designing a next-generation vaccine that induces protective immunity without the adverse side effects of a whole-cell vaccine (wPV). Here we describe a protocol that we used to test the efficacy of a promising, novel adjuvant that skews immune responses to a protective Th1/Th17 phenotype and promotes a better clearance of a B. pertussis challenge from the murine respiratory tract. This article describes the protocol for mouse immunization, bacterial inoculation, tissue harvesting, and analysis of immune responses. Using this method, within our model, we have successfully elucidated crucial mechanisms elicited by a promising, next-generation acellular pertussis vaccine. This method can be applied to any infectious disease model in order to determine vaccine efficacy.

Here we present an elegant protocol for in vivo evaluation of vaccine effectiveness and host immune responses. This protocol can be adapted for vaccine models that study viral, bacterial, or parasitic pathogens.

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a ...

Imaging of In Situ Interferon Gamma Production in the Mouse Spleen following Listeria monocytogenes Infection

Cytokines are small proteins secreted by cells, mediating cell-cell communications that are crucial for effective immune responses. One characteristic of cytokines is their pleiotropism, as they are produced by and can affect a multitude of cell types. As such, it is important to understand not only which cells are producing cytokines, but also in which environment they do so, in order to define more specific therapeutics. Here, we describe a method to visualize cytokine production in situ following bacterial infection. This technique relies on imaging cytokine-producing cells in their native environment by confocal microscopy. To do so, tissue sections are stained for markers of multiple cell types together with a cytokine stain. Key to this method, cytokine secretion is blocked directly in vivo before harvesting the tissue of interest, allowing for detection of the cytokine that accumulated inside the producing cells. The advantages of this method are multiple. First, the microenvironment in which cytokines are produced is preserved, which could ultimately inform on the signals required for cytokine production and the cells affected by those cytokines. In addition, this method gives an indication of the location of the cytokine production in vivo, as it does not rely on artificial in vitro re-stimulation of the producing cells. However, it is not possible to simultaneously analyze cytokine downstream signaling in cells that receive the cytokine. Similarly, the cytokine signals observed correspond&#160;only to the time-window during which cytokine secretion was blocked. While we describe the visualization of the cytokine Interferon (IFN) gamma in the spleen following mouse infection by the intracellular bacteria Listeria monocytogenes, this method could potentially be adapted to the visualization of any cytokine in most organs.

Imaging of In Situ Interferon Gamma Production in the Mouse Spleen following Listeria monocytogenes Infection

Here, we describe a simple confocal imaging method to visualize the in situ localization of cells secreting the cytokine Interferon gamma in murine secondary lymphoid organs. This protocol can be extended for the visualization of other cytokines in diverse tissues.

Cytokines are small proteins secreted by cells, mediating cell-cell communications that are crucial for effective immune responses. One characteristic of ...