Name: generation of marked and markerless mutants in model cyanobacterial species
Uploaded: 2016-05-29T15:00:00
Description: Watch this Scientific Journal Video about Generation of Marked and Markerless Mutants in Model Cyanobacterial Species at JoVE.com

We are grateful to the Environmental Services Association Education Trust, the Synthetic Biology in Cambridge SynBio fund and the Ministry of Social Justice and Empowerment, Government of India, for financial support.

1. Preparation of Culture Media
<ol>
	<li>Prepare BG11 medium according to Castenholz, 198817.
	<ol>
		<li>Prepare stock solutions of 100x BG11, trace elements and iron stock (Table 1).</li>
		<li>Prepare separate solutions of phosphate stock, Na2CO3 stock, N-[Tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid (TES) buffer and NaHCO3 (Table 1).</li>
		<li>Autoclave the phosphate and Na2CO3 stocks. Filter-ster...

<ol>
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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antialgal,+antibacterial+and+antifungal+activity+of+two+metabolites+produced+and+excreted+by+cyanobacteria+during+growth.">Antialgal, antibacterial and antifungal activity of two metabolites produced and excreted by cyanobacteria during growth.</a> Microbiol Res. 161, 180-186 (2006).</li><li>Scott, S. A., 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=Biodiesel+from+algae:+challenges+and+prospects.">Biodiesel from algae: challenges and prospects.</a> Curr Opin Biotechnol. 21, 277-286 (2010).</li><li>Lea-Smith, D. J., 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=Phycobilisome-deficient+strains+of+Synechocystis+sp.+PCC+6803+have+reduced+size+and+require+carbon-limiting+conditions+to+exhibit+enhanced+productivity.">Phycobilisome-deficient strains of Synechocystis sp. PCC 6803 have reduced size and require carbon-limiting conditions to exhibit enhanced productivity.</a> Plant Physiol. 165, 705-714 (2014).</li><li>Lea-Smith, D. J., 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=Thylakoid+terminal+oxidases+are+essential+for+the+cyanobacterium+Synechocystis+sp.+PCC+6803+to+survive+rapidly+changing+light+intensities.">Thylakoid terminal oxidases are essential for the cyanobacterium Synechocystis sp. PCC 6803 to survive rapidly changing light intensities.</a> Plant Physiol. 162, 484-495 (2013).</li><li>Liu, X., Sheng, J., Curtiss, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fatty+acid+production+in+genetically+modified+cyanobacteria.">Fatty acid production in genetically modified cyanobacteria.</a> Proc Natl Acad Sci U S A. 108, 6899-6904 (2011).</li><li>Xu, H., Vavilin, D., Funk, C., Vermaas, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+deletions+of+small+cab-like+proteins+in+the+cyanobacterium+Synechocystis+sp+PCC+6803+-+Consequences+for+pigment+biosynthesis+and+accumulation.">Multiple deletions of small cab-like proteins in the cyanobacterium Synechocystis sp PCC 6803 - Consequences for pigment biosynthesis and accumulation.</a> J Biol Chem. 279, 27971-27979 (2004).</li><li>Castenholz, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culturing+methods+for+Cyanobacteria.">Culturing methods for Cyanobacteria.</a> Method Enzymol. 167, 68-93 (1988).</li><li>Mitschke, J., 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=An+experimentally+anchored+map+of+transcriptional+start+sites+in+the+model+cyanobacterium+Synechocystis+sp+PCC6803.">An experimentally anchored map of transcriptional start sites in the model cyanobacterium Synechocystis sp PCC6803.</a> Proc Natl Acad Sci U S A. 108, 2124-2129 (2011).</li><li>Ried, J. L., Collmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+nptI-sacB-sacR+cartridge+for+constructing+directed,+unmarked+mutations+in+gram-negative+bacteria+by+marker+exchange-eviction+mutagenesis.">An nptI-sacB-sacR cartridge for constructing directed, unmarked mutations in gram-negative bacteria by marker exchange-eviction mutagenesis.</a> Gene. 57, 239-246 (1987).</li><li>Vieira, J., Messing, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pUC+plasmids,+an+M13mp7-derived+system+for+insertion+mutagenesis+and+sequencing+with+synthetic+universal+primers.">The pUC plasmids, an M13mp7-derived system for insertion mutagenesis and sequencing with synthetic universal primers.</a> Gene. 19, 259-268 (1982).</li><li>Vermaas, W. F. J., Williams, J. G. K., Rutherford, A. W., Mathis, P., Arntzen, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+Engineered+Mutant+of+the+Cyanobacterium+Synechocystis+6803+Lacks+the+Photosystem-Ii+Chlorophyll-Binding+Protein+Cp-47.">Genetically Engineered Mutant of the Cyanobacterium Synechocystis 6803 Lacks the Photosystem-Ii Chlorophyll-Binding Protein Cp-47.</a> Proc Natl Acad Sci U S A. 83, 9474-9477 (1986).</li><li>Westphal, S., Heins, L., Soll, J., Vothknecht, U. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vipp1+deletion+mutant+of+Synechocystis:+A+connection+between+bacterial+phage+shock+and+thylakoid+biogenesis?.">Vipp1 deletion mutant of Synechocystis: A connection between bacterial phage shock and thylakoid biogenesis?.</a> Proc Natl Acad Sci U S A. 98, 4243-4248 (2001).</li><li>Zhang, S. Y., Shen, G. Z., Li, Z. K., Golbeck, J. H., Bryant, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vipp1+Is+Essential+for+the+Biogenesis+of+Photosystem+I+but+Not+Thylakoid+Membranes+in+Synechococcus+sp+PCC+7002.">Vipp1 Is Essential for the Biogenesis of Photosystem I but Not Thylakoid Membranes in Synechococcus sp PCC 7002.</a> J Biol Chem. 289, 15904-15914 (2014).</li><li>Taroncher-Oldenberg, G., Nishina, K., Stephanopoulos, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+analysis+of+the+polyhydroxyalkanoate-specific+beta-ketothiolase+and+acetoacetyl+coenzyme+A+reductase+genes+in+the+cyanobacterium+Synechocystis+sp+strain+PCC6803.">Identification and analysis of the polyhydroxyalkanoate-specific beta-ketothiolase and acetoacetyl coenzyme A reductase genes in the cyanobacterium Synechocystis sp strain PCC6803.</a> Appl Environ Microbiol. 66, 4440-4448 (2000).</li><li>Hein, S., Tran, H., Steinbuchel, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synechocystis+sp.+PCC6803+possesses+a+two-component+polyhydroxyalkanoic+acid+synthase+similar+to+that+of+anoxygenic+purple+sulfur+bacteria.">Synechocystis sp. 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The most critical steps in generation of unmarked mutants are: 1) careful plasmid design to ensure only the targeted region is altered; 2) ensuring that samples remain axenic, especially when cultured on sucrose; 3) plating transformed cells for marked mutant generation initially on BG11 agar plates lacking antibiotics, followed by addition of agar plus antibiotics 24 hr later; 4) culturing marked mutants for 4 full days prior to plating on BG11 plus sucrose agar plates: 5) ensuring that marked mutants are fully segregat...

Cyanobacteria are an evolutionarily ancient and diverse phylum of bacteria found in nearly every natural environment on Earth. In marine ecosystems they are particularly abundant and play a key role in many nutrient cycles, accounting for approximately half of carbon fixation1, the majority of nitrogen fixation2 and hundreds of millions of tons of hydrocarbon production3 in the oceans annually. Chloroplasts, the organelle responsible for photosynthesis in eukaryotic algae and plants, are likely to have evolved from a cyanobacterium that was engulfed by a host organism4. Cyanobacteria have proved useful model organisms for the study of photosynthesis, electron transport5 and biochemical pathways, many of which are conserved in plants. In addition cyanobacteria are increasingly being used for production of food, biofuels6, electricity7 and industrial compounds8, due to their highly efficient conversion of water and CO2 to biomass using solar energy9. Many species can be cultivated on non-arable land with minimal nutrients and seawater, suggesting that cyanobacteria could potentially be grown at large scale without affecting agricultural production. Certain species are also sources of natural products, including antifungal, antibacterial and anti-cancer compounds10,11.
The ability to generate mutants is key to understanding cyanobacterial photosynthesis, biochemistry and physiology, and essential for development of strains for industrial purposes. The majority of published studies generate genetically modified strains by insertion of an antibiotic resistance cassette into the site of interest. This limits the number of mutations that can be introduced into a strain, as only a few antibiotic resistance cassettes are available for use in cyanobacteria. Strains containing genes conferring antibiotic resistance cannot be used for industrial production in open ponds, which is likely to be the only cost-effective means to produce biofuels and other low value products12. The generation of unmarked mutants overcomes these limitations. Unmarked mutants contain no foreign DNA, unless intentionally included, and can be manipulated multiple times. Therefore it is possible to generate as many alterations in a strain as desired. In addition, polar effects on genes downstream of the modification site can be minimized, allowing more precise modification of the organism13.
To generate mutant strains, suicide plasmids containing two DNA fragments identical to regions in the cyanobacterial chromosome flanking the gene to be deleted (termed the 5&#39; and 3&#39; flanking regions) are first constructed. Two genes are then inserted between these flanking regions. One of these encodes an antibiotic resistance protein; the second encodes SacB, which produces levansucrase, a compound conferring sensitivity to sucrose. In the first stage of the process, marked mutants, i.e. strains containing some foreign DNA, are generated. The plasmid construct is mixed with the cyanobacterial cells and the DNA is taken up naturally by the organism. Transformants are selected by growth on agar plates containing the appropriate antibiotic and the mutant genotype verified by PCR. Suicide plasmids cannot replicate within the strain of interest. Therefore any antibiotic resistant colonies will result from a recombination event whereby the gene of interest in inserted into the chromosome. To generate unmarked mutants, the marked mutant is then mixed with a second suicide plasmid containing just the 5&#39; and 3&#39; flanking regions. However, if insertion of foreign DNA is required, a plasmid consisting of the 5&#39; and 3&#39; flanking regions with a cassette containing the genes of interest inserted between these DNA fragments, can be used. Selection is via growth on agar plates containing sucrose. As sucrose is lethal to cells when the sacB gene product is expressed, the only cells that survive are those in which a second recombination event has occurred, whereby the sucrose sensitivity gene, in addition to the antibiotic resistance gene, has been recombined out of the chromosome and onto the plasmid. As a consequence of the recombinational exchange, the flanking regions and any DNA between them are inserted into the chromosome.
We have successfully used these methods to generate multiple chromosomal mutations in the same strain of Synechocystis sp. PCC6803 (hereafter referred to as Synechocystis)13,14, to introduce single point mutations into a gene of interest13 and for expression of gene cassettes. While generation of unmarked knockouts has been demonstrated prior to our work in Synechocystis15,16, a detailed method, aided by a visual presentation of the critical steps, is not publicly available. We have also applied the same method for generation of marked knockouts in another model cyanobacterium, Synechococcus sp. PCC7002 (hereafter referred to as Synechococcus). This protocol provides a clear, simple method for generating mutants and a rapid protocol for validating and storing these strains.

<table border="0" cellpadding="0" cellspacing="0" width="645">
	<tbody>
		<tr height="25">
			<td height="25" style="height:25px;width:237px;">NaNO3</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">S5506</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">MgSO4.7H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">230391</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CaCl2</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">C1016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">citric acid</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">C0759</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2EDTA</td>
			<td style="width:123px;">Fisher</td>
			<td style="width:119px;">EDT002</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">H3BO3</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">339067</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">MnCl2.4H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">M3634</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">ZnSO4.7H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">Z4750</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2MoO4.2H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">331058</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CuSO4.5H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">209198</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Co(NO3)2.6H2O</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">239267</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ferric ammonium citrate</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">F5879</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">K2HPO4</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">P3786</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2CO3</td>
			<td style="width:123px;">Fisher</td>
			<td style="width:119px;">SODC001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TES</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">T1375</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">NaHCO3</td>
			<td style="width:123px;">Fisher</td>
			<td style="width:119px;">SODH001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HEPES</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">H3375</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">cyanocobalamin</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">47869</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2S2O3</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">72049</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Bacto agar</td>
			<td style="width:123px;">BD</td>
			<td style="width:119px;">214010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Sucrose</td>
			<td style="width:123px;">Fisher</td>
			<td style="width:119px;">SUC001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Petri dish 90 mm triple vented</td>
			<td style="width:123px;">Greiner</td>
			<td style="width:119px;">633185</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.2 &#181;m filters</td>
			<td style="width:123px;">Sartorius</td>
			<td style="width:119px;">16534</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">100 mL conical flasks</td>
			<td style="width:123px;">Pyrex</td>
			<td style="width:119px;">CON004</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Parafilm M 100 mm x38 m</td>
			<td style="width:123px;">Bemis</td>
			<td style="width:119px;">FIL003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phusion high fidelity DNA polymerase&#160;</td>
			<td style="width:123px;">Phusion</td>
			<td style="width:119px;">F-530</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Agarose</td>
			<td style="width:123px;">Melford</td>
			<td style="width:119px;">MB1200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNA purification kit&#160;</td>
			<td style="width:123px;">MoBio</td>
			<td style="width:119px;">12100-300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Restriction endonucleases</td>
			<td style="width:123px;">NEB</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">T4 ligase</td>
			<td style="width:123px;">Thermo Scientific</td>
			<td style="width:119px;">EL0011</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Luria Bertani broth</td>
			<td style="width:123px;">Invitrogen</td>
			<td style="width:119px;">12795-027</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">MES</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">M8250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Kanamycin sulfate</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">60615</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Ampicillin</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">A9518</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">GeneJET plasmid miniprep kit</td>
			<td style="width:123px;">Thermo Scientific</td>
			<td style="width:119px;">K0503</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">14 mL round-bottom tube</td>
			<td style="width:123px;">BD falcon</td>
			<td style="width:119px;">352059</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">GoTaq G2 Flexi DNA polymerase</td>
			<td style="width:123px;">Promega</td>
			<td style="width:119px;">M7805</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">425-600 &#181;m glass beads</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">G8772</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Glycerol</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">G5516</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">DMSO</td>
			<td style="width:123px;">Sigma</td>
			<td style="width:119px;">D8418</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Fluorescent bulbs</td>
			<td style="width:123px;">Gro-Lux</td>
			<td style="width:119px;">69</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">HT multitron photobioreactor</td>
			<td style="width:123px;">Infors</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

generation of marked and markerless mutants in model cyanobacterial species

Cyanobacteria are ecologically important organisms and potential platforms for production of biofuels and useful industrial products. Genetic manipulation of cyanobacteria, especially model organisms such as Synechocystis sp. PCC6803 and Synechococcus sp. PCC7002, is a key tool for both basic and applied research. Generation of unmarked mutants, whereby chromosomal alterations are introduced into a strain via insertion of an antibiotic resistance cassette (a manipulatable fragment of DNA containing one or more genes), followed by subsequent removal of this cassette using a negative selectable marker, is a particularly powerful technique. Unmarked mutants can be repeatedly genetically manipulated, allowing as many alterations to be introduced into a strain as desired. In addition, the absence of genes encoding antibiotic resistance proteins in the mutated strain is desirable, as it avoids the possibility of 'escape' of antibiotic resistant organisms into the environment. However, detailed methods for repeated rounds of genetic manipulation of cyanobacteria are not well described in the scientific literature. Here we provide a comprehensive description of this technique, which we have successfully used to generate mutants with multiple deletions, single point mutations within a gene of interest and insertion of novel gene cassettes.

Plasmid design is critical for successful generation of both marked and unmarked mutants. Figure 1 gives an example of plasmid A and B used to generate a deletion mutant in the Synechocystis genes cpcC1 and cpcC213. In each case the 5&#39; and 3&#39; flanking regions are approximately 900-1,000 bp. Reduced flanking regions can be used although the smallest we have successfully trialed has been approximately 500 bp. Plasmid B can also ...

Watch this Scientific Journal Video about Generation of Marked and Markerless Mutants in Model Cyanobacterial Species at JoVE.com

Generation of Marked and Markerless Mutants in Model Cyanobacterial Species

Introducing multiple genomic alterations into cyanobacteria is an essential tool in the development of strains for industrial and basic research purposes. We describe a system for generating unmarked mutants in the model cyanobacterial species Synechocystis sp. PCC6803 and marked mutants in Synechococcus sp. PCC7002.

Cyanobacteria are ecologically important organisms and potential platforms for production of biofuels and useful industrial products. Genetic manipulation ...

The overall goal of this procedure is to demonstrate a system for generating unmarked mutants in the cyanobacterial Synechocystis species PCC6803 and marked mutants in Synechococcus species PCC7002. This method can help answer key questions in the cyanobacterial genetics field. Such as how to introduce chromosomal alterations into a strain.By insertion of an antibiotic resistance gene, followed by a subsequent removal of this cassette, using a negative selectable marker. The main advantage of this technique is that strains can be repeatedly genetically manipulated. Allowing as many alternations to be introduced into a strain as desired.After preparing media, cyanobacterial strains and plasmids, according to the text protocol. Set up a fresh culture by inoculating a loop full of cyanobacterial cells, into 30 to 50 mililiters of BG11 medium. Grow the culture in the light at 30 degrees Celsius for two to three days, to an OD7500, equal to 0.2 to 0.6.Following the incubation, centrifuge one to two milliliters of the culture at 2, 300g's for five minutes. Then after discarding the supernatant, use BG11 medium to wash the pellets once, gently pipetting to resuspend the cells. As vortexing may result in the loss of pili, which are essential for DNA uptake.After pelleting the cells again, and removing the supernatant, add BG11 medium to a final volume of 100 microliters, and transfer the cells to a 14 milliliter round bottom tube. Next, add 1 microgram of previous prepared plasmid A to the cells. And gently tap to mix.Then lay the tubes down horizontally in the incubator at 30 degrees Celsius, and incubate for four to six hours. Following the incubation, spread aliquots of the cell culture plasmid DNA mixture on BG11 agar plates without antibiotics. And incubate at 30 degrees Celsius.Approximately 24 hours later, prepare a 0.6%agar solution, in water containing kanamycin. And allow it to cool to 42 degress Celsius. Then add 2.5 to three milliliters to the edges of the culture plates and tilt the plate, so the solution forms an even top agar layer on the surface.Incubate the plates approximately seven days for colonies to be visible. Then divide a fresh BG11 agar plus kanamycin plate into six sectors. And use a blunt end toothpick to streak out individual colonies.To carry out PCR, to confirm marked knockout, transfer a small amount of cells into a tube containing 50 microliters of water, and approximately 20 425 to 600 micrometer glass beads. Shake the cells and beads at approximately 2, 000 rpm for five minutes, before spinning at 15, 700 g's for five minutes. Then use five microliters of the supernatant to prepare 50 microliter PCR reactions with tack DNA preliminaries.To validate the mutants, after designing primers according to the text protocol, amplified product using the following program, and include a wild-type control. Through gelelektroforeses, verify the genotype of knockout transformants. Showing a band of approximately four kilobase pairs and lacking the wild-type band.Refer to the text protocol for further details. If a wild-type band is still present, re-streak the strain on the fresh plate and repeat the PCR. Repeat the validation process until the mutant is segregated, and no wild-type band is observed in the PCR reaction.For a strain that shows marked mutant profile, re-streak on a fresh plate for use in generating an unmarked knockout. To generate unmarked Synechocystis mutants, set up a fresh culture of the marked knockout by inoculating the loop full of cells into 30 to 50 milliliters of BG11 medium. Grow the culture for two to three days to and OD750, equal to 0.2 to 0.6.Centrifuge 10 milliliters of the culture at 2, 300 g's for five minutes and discard the supernatant. Then us BG11 medium to gently wash the cells. After adding BG11 to a final volume of 200 microliters, and transferring the cells to a 14 milliliter round bottom tube, add 1 microgram of plasmid B DNA to the cells, and gently tap to mix.Then lay the tubes down horizontally in the incubator, and incubate for four to six hours. Following the incubation, add 1.8 milliliters of BG11 medium and incubate the samples for a total of four days with shaking. This is a sufficient time to allow recombination to occur in the multiple chromosomal copies.Plate 50, 10, and 1 microliter aliquots of the transformed culture onto BG11 plus 5%sucrose agar plates and incubate for approximately seven days to generate single colonies. Next, using a blunt end toothpick, hatch 30 to 50 individual colonies on BG11 plus kanamycin plates. Then patch onto BG11 plus 5%sucrose.Colonies that grow on BG11 plus sucrose, but not on plates with kanamycin are potential unmarked knockouts. Colonies that grow on both plates are likely to be sucrose resistant due to a mutation in the sacB gene. Following the PCR method, demonstrated earlier in this video, verify unmarked knockouts, which will produce a gel band corresponding to the wild-type size minus the deleted region.If the strain shows an unmarked mutant profile, then re-streak it on fresh BG11 agar without antibiotics. To store the strains long term, set up a fresh culture of the strain by inoculating a loop full of cells into 30 to 50 milliliters of BG11 medium. Grow the culture for three to four days to and OD750 equal to 0.4 to 0.7.After using BG11 to wash the cells once, resuspend the pellet in approximately two milliliters of BG11. Add 0.8 milliliters of the concentrated cells to one tube. Then add 0.2 milliliters of 80%filter sterilized glycerol.To another tube, add 0.93 milliliters of concentrated cells and 0.07 milliliters of DMSO. Store both tubes at negative 80 degrees Celsius. To revive the strains, remove the tube and use a blunt end toothpick to scrape off some cells onto an agar plate without antibiotics.Then use a sterile loop to streak out as normal. This figure shows examples of plasmids A and B used to generate deletion mutants. In each case, the five prime and three prime planking regions are approximately 900 to 1, 000 base pairs.Plasmid B, can also contain a gene cassette between the five prime and three prime approximately one kilobase pair flanking regions. Or a modified version of the native gene sequence. Upon transformation with plasmid A, several hundred colonies will appear on a plate after seven to 10 days.If genes are non-essential and mutants demonstrate growth, similar to the wild-type strain, then all of the chromosomes should contain a copy npt1/sacB inserted sequence, as determined via PCR. If genes are non-essential, and mutants grow slow, then several rounds of re-streaking with increasing concentrations of kanamycin, are necessary to obtain a segregated marked mutant. If upon re-streaking, a marked mutant is not obtained, the gene is likely essential for survival.The majority of individual colonies, obtained from transformation with plasmid B, will be kanamycin sensitive and sucrose resistant. As demonstrated here, PCR amplification of the target region in these colonies, shows that nearly 100%of the unmarked mutant profile. Once mastered, this technique can be done in hours over a six week period if it is performed properly.While attempting this procedure it's important to remember to use sterile technique. Following this procedure, other methods like measuring oxygen production, or gas chromatography mass spectrometry, can be performed in order to answer additional questions, like measuring photosynthetic rates or metabolite production. After its development, this technique paved the way for researchers in the field of cyanobacterial genetics.To explore key biochemical and physiological processes in this phylum, and developmental strains for industrial purposes. After watching this video, you should have a good understanding of how to generate unmarked knockouts in Synechococcus species PCC6803.

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Research

JoVE Journal

Biology

Neurocircuit Assays for Seizures in Epilepsy Mutants of Drosophila

Drosophila melanogaster is a useful tool for studying seizure like activity. A variety of mutants in which seizures can be induced through either physical shock or electrical stimulation is available for study of various aspects of seizure activity and behavior. All flies, including wild-type, will undergo seizure-like activity if stimulated at a high enough voltage. Seizure like activity is an all-or-nothing response and each genotype has a specific seizure threshold. The seizure threshold of a specific genotype of fly can be altered either by treatment with a drug or by genetic suppression or enhancement. The threshold is easily measured by electrophysiology. Seizure-like activity can be induced via high frequency electrical stimulation delivered directly to the brain and recorded through the dorsal longitudinal muscles (DLMs) in the thorax. The DLMs are innervated by part of the giant fiber system. Starting with low voltage, high frequency stimulation, and subsequently raising the voltage in small increments, the seizure threshold for a single fly can be measured.

Neurocircuit Assays for Seizures in Epilepsy Mutants of Drosophila

Using high frequency electrical stimulation, seizure-like activity can be induced in Drosophila. This activity is easily recorded from the giant fiber system.

Drosophila melanogaster is a useful tool for studying seizure like activity. A variety of mutants in which seizures can be induced through either physical ...

Lens Transplantation in Zebrafish and its Application in the Analysis of Eye Mutants

The lens plays an important role in the development of the optic cup[1,2]. Using the zebrafish as a model organism, questions regarding lens development can be addressed. The zebrafish is useful for genetic studies due to several advantageous characteristics, including small size, high fecundity, short lifecycle, and ease of care. Lens development occurs rapidly in zebrafish. By 72 hpf, the zebrafish lens is functionally mature [3]. Abundant genetic and molecular resources are available to support research in zebrafish. In addition, the similarity of the zebrafish eye to those of other vertebrates provides basis for its use as an excellent animal model of human defects[4-7]. Several zebrafish mutants exhibit lens abnormalities, including high levels of cell death, which in some cases leads to a complete degeneration of lens tissues [8]. To determine whether lens abnormalities are due to intrinsic causes or to defective interactions with the surrounding tissues, transplantation of a mutant lens into a wild-type eye is performed. Using fire-polished metal needles, mutant or wild-type lenses are carefully dissected from the donor animal, and transferred into the host. To distinguish wild-type and mutant tissues, a transgenic line is used as the donor. This line expresses membrane-bound GFP in all tissues, including the lens. This transplantation technique is an essential tool in the studies of zebrafish lens mutants.

Lens development involves interactions with other tissues. Several zebrafish eye mutants are characterized by an abnormally small lens size. Here we demonstrate a lens transplantation experiment to determine whether this phenotype is due to intrinsic causes or defective interactions with tissues that surround the lens.

The lens plays an important role in the development of the optic cup[1,2]. Using the zebrafish as a model organism, questions regarding lens development ...

A Noninvasive Hair Sampling Technique to Obtain High Quality DNA from Elusive Small Mammals

Noninvasive genetic sampling approaches are becoming increasingly important to study wildlife populations. A number of studies have reported using noninvasive sampling techniques to investigate population genetics and demography of wild populations1. This approach has proven to be especially useful when dealing with rare or elusive species2. While a number of these methods have been developed to sample hair, feces and other biological material from carnivores and medium-sized mammals, they have largely remained untested in elusive small mammals. In this video, we present a novel, inexpensive and noninvasive hair snare targeted at an elusive small mammal, the American pika (Ochotona princeps). We describe the general set-up of the hair snare, which consists of strips of packing tape arranged in a web-like fashion and placed along travelling routes in the pikas&#x2019; habitat. We illustrate the efficiency of the snare at collecting a large quantity of hair that can then be collected and brought back to the lab. We then demonstrate the use of the DNA IQ system (Promega) to isolate DNA and showcase the utility of this method to amplify commonly used molecular markers including nuclear microsatellites, amplified fragment length polymorphisms (AFLPs), mitochondrial sequences (800bp) as well as a molecular sexing marker. Overall, we demonstrate the utility of this novel noninvasive hair snare as a sampling technique for wildlife population biologists. We anticipate that this approach will be applicable to a variety of small mammals, opening up areas of investigation within natural populations, while minimizing impact to study organisms.

We present a noninvasive sampling approach to efficiently collect hair samples from elusive small mammals, as shown for the American pika. We demonstrate the utility of this method by extracting DNA from sampled hair and amplifying several types of molecular markers commonly used in studies of wildlife ecology and conservation.

Noninvasive genetic sampling approaches are becoming increasingly important to study wildlife populations. A number of studies have reported using ...

Generation, Purification, and Characterization of Cell-invasive DISC1 Protein Species

Protein aggregation is seen as a general hallmark of chronic, degenerative brain conditions like, for example, in the neurodegenerative diseases Alzheimer's disease (A&beta;, tau), Parkinson's Disease (&alpha;-synuclein), Huntington's disease (polyglutamine, huntingtin), and others. Protein aggregation is thought to occur due to disturbed proteostasis, i.e. the imbalance between the arising and degradation of misfolded proteins. Of note, the same proteins are found aggregated in sporadic forms of these diseases that are mutant in rare variants of familial forms.
Schizophrenia is a chronic progressive brain condition that in many cases goes along with a permanent and irreversible cognitive deficit. In a candidate gene approach, we investigated whether Disrupted-in-schizophrenia 1 (DISC1), a gene cloned in a Scottish family with linkage to chronic mental disease1, 2, could be found as insoluble aggregates in the brain of sporadic cases of schizophrenia3. Using the SMRI CC, we identified in approximately 20 % of cases with CMD but not normal controls or patients with neurodegenerative diseases sarkosyl-insoluble DISC1 immunoreactivity after biochemical fractionation. Subsequent studies in vitro revealed that the aggregation propensity of DISC1 was influenced by disease-associated polymorphism S704C4, and that DISC1 aggresomes generated in vitro were cell-invasive5, similar to what had been shown for A&beta;6, tau7-9, &alpha;-synuclein10, polyglutamine11, or SOD1 aggregates12. These findings prompted us to propose that at least a subset of cases with CMD, those with aggregated DISC1 might be protein conformational disorders.
 Here we describe how we generate DISC1 aggresomes in mammalian cells, purify them on a sucrose gradient and use them for cell-invasiveness studies. Similarly, we describe how we generate an exclusively multimeric C-terminal DISC1 fragment, label and purify it for cell invasiveness studies. Using the recombinant multimers of DISC1 we achieve similar cell invasiveness as for a similarly labeled synthetic &alpha;-synuclein fragment. We also show that this fragment is taken up in vivo when stereotactically injected into the brain of recipient animals.

The generation, purification and cell invasion of intracellular, cytoplasmic full length DISC1 protein aggresomes from cell cultures and of a labeled, multimeric recombinant DISC1 protein fragment in E. coli are described. Cell invasiveness is shown for recipient cells in cell culture and for neurons in vivo after stereotactical brain inoculation.

Protein aggregation is seen as a general hallmark of chronic, degenerative brain conditions like, for example, in the neurodegenerative diseases ...

Detecting, Visualizing and Quantitating the Generation of Reactive Oxygen Species in an Amoeba Model System

Reactive oxygen species (ROS) comprise a range of reactive and short-lived, oxygen-containing molecules, which are dynamically interconverted or eliminated either catalytically or spontaneously. Due to the short life spans of most ROS and the diversity of their sources and subcellular localizations, a complete picture can be obtained only by careful measurements using a combination of protocols. Here, we present a set of three different protocols using OxyBurst Green (OBG)-coated beads, or dihydroethidium (DHE) and Amplex UltraRed (AUR), to monitor qualitatively and quantitatively various ROS in professional phagocytes such as Dictyostelium. We optimised the beads coating procedures and used OBG-coated beads and live microscopy to dynamically visualize intraphagosomal ROS generation at the single cell level. We identified lipopolysaccharide (LPS) from E. coli as a potent stimulator for ROS generation in Dictyostelium. In addition, we developed real time, medium-throughput assays using DHE and AUR to quantitatively measure intracellular superoxide and extracellular H2O2 production, respectively.

We adapted a set of protocols for the measurement of reactive oxygen species (ROS) that can be applied in various amoeba and mammalian cellular models for qualitative and quantitative studies.

Reactive oxygen species (ROS) comprise a range of reactive and short-lived, oxygen-containing molecules, which are dynamically interconverted or ...

Rapid and Efficient Zebrafish Genotyping Using PCR with High-resolution Melt Analysis

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic tools have been introduced, including multiple strategies for inducing mutations and generating transgenic lines. However, large-scale screening is limited by traditional genotyping methods, which are time-consuming and labor-intensive. Here we describe a technique to analyze zebrafish genotypes by PCR combined with high-resolution melting analysis (HRMA).&#160;This approach is rapid, sensitive, and inexpensive, with lower risk of contamination artifacts.&#160;Genotyping by PCR with HRMA can be used for embryos or adult fish, including in high-throughput screening protocols.

PCR combined with high-resolution melt analysis (HRMA) is demonstrated as a rapid and efficient method to genotype zebrafish.

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic ...

Efficient Generation Human Induced Pluripotent Stem Cells from Human Somatic Cells with Sendai-virus

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs include modeling pathogenesis of human genetic diseases, autologous cell therapy after gene correction, and personalized drug screening by providing a source of patient-specific and symptom relevant cells. However, there are several hurdles to overcome, such as eliminating the remaining reprogramming factor transgene expression after human iPSCs production. More importantly, residual transgene expression in undifferentiated human iPSCs could hamper proper differentiations and misguide the interpretation of disease-relevant in vitro phenotypes. With this reason, integration-free and/or transgene-free human iPSCs have been developed using several methods, such as adenovirus, the piggyBac system, minicircle vector, episomal vectors, direct protein delivery and synthesized mRNA. However, efficiency of reprogramming using integration-free methods is quite low in most cases.
Here, we present a method to isolate human iPSCs by using Sendai-virus (RNA virus) based reprogramming system. This reprogramming method shows consistent results and high efficiency in cost-effective manner.

Here, we present our established method to reprogram human somatic cells into transgene-free human iPSCs with Sendai virus, which shows consistent outcome and enhanced efficiency.

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs ...

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and temporal resolution to study in vivo hematopoiesis using the murine bone marrow transplant experimental model. Genetic combinatorial marking using lentiviral vectors encoding fluorescent proteins (FPs) enabled cell fate mapping through advanced microscopy imaging. Vectors encoding five different FPs: Cerulean, EGFP, Venus, tdTomato, and mCherry were used to concurrently transduce HSPCs, creating a diverse palette of color marked cells. Imaging using confocal/two-photon hybrid microscopy enables simultaneous high resolution assessment of uniquely marked cells and their progeny in conjunction with structural components of the tissues. Volumetric analyses over large areas reveal that spectrally coded HSPC-derived cells can be detected non-invasively in various intact tissues, including the bone marrow (BM), for extensive periods of time following transplantation. Live studies combining video-rate multiphoton and confocal time-lapse imaging in 4D demonstrate the possibility of dynamic cellular and clonal tracking in a quantitative manner.

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

Combinatorial 5 fluorescent proteins marking of hematopoietic stem and progenitor cells allows in vivo clonal tracking via confocal and two-photon microscopy, providing insights into bone marrow hematopoietic architecture during regeneration. This method allows non-invasive fate mapping of spectrally-coded HSPCs-derived cells in intact tissues for extensive periods of time following transplantation.

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and ...

Microbiota Analysis Using Two-step PCR and Next-generation 16S rRNA Gene Sequencing

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the immune system. Perturbation of the healthy gut microbiome has been suggested to play a role in the development of inflammatory diseases, including multiple sclerosis (MS). Environmental and genetic factors can influence the composition of the microbiome; therefore, identification of microbial communities linked with a disease phenotype has become the first step towards defining the microbiome&#8217;s role in health and disease. Use of 16S rRNA metagenomic sequencing for profiling bacterial community has helped in advancing microbiome research. Despite its wide use, there is no uniform protocol for 16S rRNA-based taxonomic profiling analysis. Another limitation is the low resolution of taxonomic assignment due to technical difficulties such as smaller sequencing reads, as well as use of only forward (R1) reads in the final analysis due to low quality of reverse (R2) reads. There is need for a simplified method with high resolution to characterize bacterial diversity in a given biospecimen. Advancements in sequencing technology with the ability to sequence longer reads at high resolution have helped to overcome some of these challenges. Present sequencing technology combined with a publicly available metagenomic analysis pipeline such as R-based Divisive Amplicon Denoising Algorithm-2 (DADA2) has helped advance microbial profiling at high resolution, as DADA2 can assign sequence at the genus and species levels. Described here is a guide for performing bacterial profiling using two-step amplification of the V3-V4 region of the 16S rRNA gene, followed by analysis using freely available analysis tools (i.e., DADA2, Phyloseq, and METAGENassist). It is believed that this simple and complete workflow will serve as an excellent tool for researchers interested in performing microbiome profiling studies.

Described here is a simplified standard operating procedure for microbiome profiling using 16S rRNA metagenomic sequencing and analysis using freely available tools. This protocol will help researchers who are new to the microbiome field as well as those requiring updates on methods to achieve bacterial profiling at a higher resolution.

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the ...

Preparing Irradiated and Marked Male Aedes aegypti Mosquitoes for Release in an Operational Sterile Insect Technique Program

The control of such human diseases as dengue, Zika, and chikungunya relies on the control of their vector, the Aedes aegypti mosquito, because there is no prevention. Control of mosquito vectors can rely on chemicals applied to the immature and adult stages, which can contribute to the mortality of non-targets and more importantly, lead to insecticide resistance in the vector. The sterile insect technique (SIT) is a method of controlling populations of pests through the release of sterilized adult males that mate with wild females to produce non-viable offspring. This paper describes the process of producing sterile males for use in an operational SIT program for the control of Aedes aegypti mosquitoes. Outlined here are the steps used in the program including rearing and maintaining a colony, separating male and female pupae, irradiating and marking adult males, and shipping Aedes aegypti males to the release site. Also discussed are procedural caveats, program limitations, and future objectives.

Preparing Irradiated and Marked Male Aedes aegypti Mosquitoes for Release in an Operational Sterile Insect Technique Program

The sterile insect technique (SIT) is used to control specific, medically important mosquito populations that may be resistant to chemical controls. Here, we describe a method of mass rearing and preparation of sterile male mosquitoes for release in an operational SIT program targeting the Aedes aegypti mosquito.

The control of such human diseases as dengue, Zika, and chikungunya relies on the control of their vector, the Aedes aegypti mosquito, because there is no ...