Name: Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux&#45;Deficient Bacterial Strain and a Single&#45;Copy Gene Expression System
Uploaded: 2024-01-05T15:00:00
Description: Watch this Scientific Journal Video about Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System at JoVE.com

This work was supported by a Discovery Grant from the Natural Science and Engineering Council of Canada to AK. The schematics used in the figures are created with BioRender.com.

1. Experimental preparation
<ol>
	<li>Purify the plasmid pUC18T-mini-Tn7T-LAC-Gm9 (insertion plasmid, Figure 2A) with the gene of interest. 
	NOTE: Here, the gene of interest is adeIJK. The final plasmid concentration should be &#8805;100 ng/&#181;L.</li>
	<li>Purify the helper plasmid (pTNS2)9 and the excision plasmid (pFLP2ab)6 (Figure 2B...

Single&#45;Copy Gene Expression for Characterizing Multidrug Efflux Systems

<ol>
	<li>Prioritization of pathogens to guide research, discovery, research and development of new antibiotics for drug-resistant bacterial infections, including tuberculosis. World Health Organization Available from: <a target="_blank" href="https://www.who.int/publications/i/item/WHO-EMP-IAU-2017.12">https://www.who.int/publications/i/item/WHO-EMP-IAU-2017.12</a> (2017)</li><li>Kornelsen, V., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Update+on+multidrug+resistance+efflux+pumps+in+Acinetobacter+spp.">Update on multidrug resistance efflux pumps in Acinetobacter spp.</a> Antimicrob Agents Chemother. 65 (7), e00514-00521 (2021).</li><li>Sykes, E. M., Deo, S., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+genetic+tools+for+Acinetobacter+baumannii.">Recent advances in genetic tools for Acinetobacter baumannii.</a> Front Genet. 11, 601380 (2020).</li><li>Kumar, A., Chua, K. L., Schweizer, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+regulated+expression+of+single-copy+efflux+pump+genes+in+a+surrogate+Pseudomonas+aeruginosa+strain:+identification+of+the+BpeEF-OprC+chloramphenicol+and+trimethoprim+efflux+pump+of+Burkholderia+pseudomallei+1026b.">Method for regulated expression of single-copy efflux pump genes in a surrogate Pseudomonas aeruginosa strain: identification of the BpeEF-OprC chloramphenicol and trimethoprim efflux pump of Burkholderia pseudomallei 1026b.</a> Antimicrob Agents Chemother. 50 (10), 3460-3463 (2006).</li><li>Kumar, A., Dalton, C., Cortez-Cordova, J., Schweizer, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mini-Tn7+vectors+as+genetic+tools+for+single+copy+gene+cloning+in+Acinetobacter+baumannii.">Mini-Tn7 vectors as genetic tools for single copy gene cloning in Acinetobacter baumannii.</a> J Microbiol Methods. 82 (3), 296-300 (2010).</li><li>Ducas-Mowchun, K., 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=Next+generation+of+Tn7-based+single-copy+insertion+elements+for+use+in+multi-+and+pan-drug+resistant+strains+of+Acinetobacter+baumannii.">Next generation of Tn7-based single-copy insertion elements for use in multi- and pan-drug resistant strains of Acinetobacter baumannii.</a> Appl Environ Microbiol. 85 (11), e00066-00119 (2019).</li><li>Ducas-Mowchun, K., De Silva, P. M., Patidar, R., Schweizer, H. P., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tn7-based+single-copy+insertion+vectors+for+Acinetobacter+baumannii.">Tn7-based single-copy insertion vectors for Acinetobacter baumannii.</a> Methods Mol Biol. 1946, 135-150 (2019).</li><li>Schweizer, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+the+Saccharomyces+cerevisiae+Flp-FRT+system+in+bacterial+genetics.">Applications of the Saccharomyces cerevisiae Flp-FRT system in bacterial genetics.</a> J Mol Microbiol Biotechnol. 5 (2), 67-77 (2003).</li><li>Choi, K. H., 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+Tn7-based+broad-range+bacterial+cloning+and+expression+system.">A Tn7-based broad-range bacterial cloning and expression system.</a> Nat Methods. 2 (6), 443-448 (2005).</li><li>Choi, K. H., Schweizer, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mini-Tn7+insertion+in+bacteria+with+single+attTn7+sites:+example+Pseudomonas+aeruginosa.">Mini-Tn7 insertion in bacteria with single attTn7 sites: example Pseudomonas aeruginosa.</a> Nat Protoc. 1 (1), 153-161 (2006).</li><li>Kornelsen, V., Unger, M., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atorvastatin+does+not+display+an+antimicrobial+activity+on+its+own+nor+potentiates+the+activity+of+other+antibiotics+against+Acinetobacter+baumannii+ATCC+17978+or+A.+baumannii+AB030.">Atorvastatin does not display an antimicrobial activity on its own nor potentiates the activity of other antibiotics against Acinetobacter baumannii ATCC 17978 or A. baumannii AB030.</a> Access Microbiol. 3, 000288 (2021).</li><li>Reyrat, J. 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=Counterselectable+markers:+untapped+tools+for+bacterial+genetics+and+pathogenesis.">Counterselectable markers: untapped tools for bacterial genetics and pathogenesis.</a> Infect Immun. 66 (9), 4011-4017 (1998).</li><li>Gay, P., 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=Positive+selection+procedure+for+entrapment+of+insertion+sequence+elements+in+gram-negative+bacteria.">Positive selection procedure for entrapment of insertion sequence elements in gram-negative bacteria.</a> J Bacteriol. 164, 918-921 (1985).</li><li>Kyriakidis, I., Vasileiou, E., Pana, Z. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tragiannidis,+Acinetobacter+baumannii+antibiotic+resistance+mechanisms.">Tragiannidis, Acinetobacter baumannii antibiotic resistance mechanisms.</a> Pathogens. 10 (3), 373 (2021).</li><li>Clinical and Laboratory Standards Institute. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+standards+for+antimicrobial+susceptibility+testing.">Performance standards for antimicrobial susceptibility testing.</a> CLSI Supplement M100., 31st edn. , (2021).</li><li>Dijkshoorn, L., Nemec, A., Seifert, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+increasing+threat+in+hospitals:+multidrug-resistant+Acinetobacter+baumannii.">An increasing threat in hospitals: multidrug-resistant Acinetobacter baumannii.</a> Nature Reviews Microbiology. 5, 939-951 (2007).</li><li>Yildirim, S., Thompson, M. G., Jacobs, A. C., Zurawski, D. V., Kirkup, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+parameters+for+high+efficiency+transformation+of+Acinetobacter+baumannii.">Evaluation of parameters for high efficiency transformation of Acinetobacter baumannii.</a> Sci Rep. 25 (6), 22110 (2016).</li><li>Thompson, M. G., Yildirim, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transformation+of+Acinetobacter+baumannii:+electroporation.">Transformation of Acinetobacter baumannii: electroporation.</a> Methods Mol Biol. 1946, 69-74 (2019).</li><li>Choi, K. H., DeShazer, D., Schweizer, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mini-Tn7+insertion+in+bacteria+with+multiple+glmS-linked+attTn7+sites:+example+Burkolderia+mallei+ATCC+2334.">Mini-Tn7 insertion in bacteria with multiple glmS-linked attTn7 sites: example Burkolderia mallei ATCC 2334.</a> Nat Protoc. 1 (1), 162-169 (2006).</li><li>Jittawuttipoka, T., 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=Mini-Tn7+vectors+as+genetic+tools+for+gene+cloning+at+a+single+copy+number+in+an+industrially+important+and+phytopathogenic+bacteria,+Xanthomonas+spp.">Mini-Tn7 vectors as genetic tools for gene cloning at a single copy number in an industrially important and phytopathogenic bacteria, Xanthomonas spp.</a> FEMS Microbiol Lett. 298 (1), 111-117 (2009).</li><li>P&#233;rez-Varela, M., Tierney, A. R. P., Kim, J. S., V&#225;zquez-Torres, A., Rather, P. <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+RelA+in+Acinetobacter+baumannii.">Characterization of RelA in Acinetobacter baumannii.</a> J Bacteriol. 202 (12), e00045 (2020).</li><li>Williams, C. 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=Characterization+of+Acinetobacter+baumannii+copper+resistance+reveals+a+role+in+virulence.">Characterization of Acinetobacter baumannii copper resistance reveals a role in virulence.</a> Front Microbiol. 11, 16 (2020).</li></ol>

Even though this procedure for the chromosomal insertion of an inducible single-copy gene expression system in A. baumannii is technically straightforward and not labor-intensive, there are a few important steps that need to be emphasized. First, preparation of the competent cells needs to be done on ice as much as possible as the cells become fragile during the replacement of the media with ice-cold water. Ideally, the centrifugation steps are performed at 4 &#176;C, but centrifugation at room temperature is ac...

Acinetobacter baumannii is a World Health Organization top priority pathogen due to its encompassing resistance to all classes of antibiotics1. It is an opportunistic pathogen mostly affecting hospitalized, injured, or immunocompromised people. A. baumannii largely evades antibiotics via efflux pumps, the most relevant being the Resistance-Nodulation-Division (RND) family of exporters2. Understanding how these efflux pumps work mechanistically will allow one to develop targeted therapeutic options.
One common way that cellular processes can be specifically distinguished is through genetic manipulation. However, the tools available for A. baumannii genetic studies are limited, and to further confound experimental design, clinical isolates often are resistant to the antibiotics routinely used for selection in genetic manipulations3. A second hurdle encountered when studying efflux pumps specifically is that they are strictly regulated-often by unknown factors-making it difficult to accurately isolate and attribute function to a single pump4. Seeing this need to expand the research toolbox, we developed a mini-Tn7-based, single-copy-insertion, inducible expression system that incorporates a Flp recombinase target (FRT) cassette, which allows for the removal of the selection marker5,6,7 (Figure 1). First created for Pseudomonas8,9,10, this elegant cloning and expression system was used to generate single-copy efflux pump complements into an RND efflux pump-deficient strain of A. baumannii (ATCC 17978::&#916;adeIJK,&#916;adeFGH,&#916;adeAB: hereafter referred to as A. baumannii AB258) that we generated11. Being able to study one efflux pump at a time and not overwhelm the bacterial cells with high-copy expression (as generally seen with plasmid-based expression systems), one can better learn about the critical, physiological aspects of each efflux pump with minimal interference and reduced complications.
This article describes how to use the mini-Tn7 system to complement a deleted gene of interest, RND efflux pump adeIJK, into the chromosome of A. baumannii AB258 through a series of uncomplicated steps performed over the course of 9 days7. The first set of steps re-introduces the deleted efflux pump genes cloned into the mini-Tn7-based insertion plasmid (Figure 2A) at the single attTn7 insertion site downstream of the well-conserved glmS gene (Figure 3A). This process is facilitated by a non-replicative helper plasmid (Figure 2B) that encodes for the transposase genes needed for Tn7-driven insertion. The second set of steps uses an excision plasmid (Figure 2C) for Flp recombinase-mediated removal of the gentamicin gene flanked by FRT sites (Figure 3B) to create an unmarked strain. Though this system is used to elucidate the essential roles and possible inhibitors of RND efflux pumps with respect to antibiotic resistance, it can be used to investigate any gene of interest.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.2 mL PCR tube</td>
			<td>VWR</td>
			<td>20170-012</td>
			<td>For colony boil preparations and PCR reactions</td>
		</tr>
		<tr>
			<td>1.5 mL microfuge tubes</td>
			<td>Sarstedt</td>
			<td>72-690-301</td>
			<td>General use</td>
		</tr>
		<tr>
			<td>13-mL culture tubes, Pyrex</td>
			<td>Fisher</td>
			<td>14-957K</td>
			<td>Liquid culture vessels</td>
		</tr>
		<tr>
			<td>6x DNA loading buffer</td>
			<td>Froggabio</td>
			<td>LD010</td>
			<td>Agarose gel electrophoresis sample loading dye</td>
		</tr>
		<tr>
			<td>Acetic acid, glacial</td>
			<td>Fisher</td>
			<td>351271-212</td>
			<td>Agarose gel running buffer component</td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Bioshop</td>
			<td>AGR003</td>
			<td>Solid growth media</td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>BioBasic</td>
			<td>D0012</td>
			<td>Electrophoretic separation of PCR reaction products; used at a concentration of 0.8&#8211;2%</td>
		</tr>
		<tr>
			<td>Agarose gel electrophoresis unit</td>
			<td>Fisher</td>
			<td>29-237-54</td>
			<td>Agarose gel electrophoresis; separation of PCR reaction products</td>
		</tr>
		<tr>
			<td>Carbenicillin</td>
			<td>Fisher</td>
			<td>50841231</td>
			<td>Selective media</td>
		</tr>
		<tr>
			<td>Culture tube closures</td>
			<td>Fisher</td>
			<td>13-684-138</td>
			<td>Stainless steel closure for 13-mL culture tubes</td>
		</tr>
		<tr>
			<td>Deoxynucleotide triphosphate (dNTP) set</td>
			<td>Biobasic</td>
			<td>DD0058</td>
			<td>PCR reaction component; supplied as 100 mM each dATP, dCTP, dGTP, dTTP; mixed and diluted for 10 mM each dNTP</td>
		</tr>
		<tr>
			<td>Dry bath/block heater</td>
			<td>Fisher</td>
			<td>88860023</td>
			<td>Isotemp digital dry bath for boil preparations</td>
		</tr>
		<tr>
			<td>Electroporation cuvettes</td>
			<td>VWR</td>
			<td>89047-208</td>
			<td>2 mm electroporation cuvettes with round cap</td>
		</tr>
		<tr>
			<td>Electroporator</td>
			<td>Cole Parmer</td>
			<td>940000009</td>
			<td>110 VAC, 60 Hz electroporator</td>
		</tr>
		<tr>
			<td>Ethidium bromide</td>
			<td>Fisher</td>
			<td>BP102-1</td>
			<td>Visualization of PCR reaction products and DNA marker in agarose gel</td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (EDTA)</td>
			<td>VWR</td>
			<td>CA-EM4050</td>
			<td>Agarose gel running buffer component</td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>Biobasic</td>
			<td>GB0217</td>
			<td>For the preparation of selective media</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Fisher</td>
			<td>G33</td>
			<td>Preparation of bacterial stocks for long-term storage in an ultra-low freezer</td>
		</tr>
		<tr>
			<td>Incubator (shaking)</td>
			<td>New Brunswick Scientific</td>
			<td>M1352-0000</td>
			<td>Excella E24 Incubator Shaker for liquid culture growth</td>
		</tr>
		<tr>
			<td>Incubator (static)</td>
			<td>Fisher</td>
			<td>11-690-550D</td>
			<td>Isotemp Incubator Oven Model 550D for solid (LB agar) culture growth</td>
		</tr>
		<tr>
			<td>Inoculation loop</td>
			<td>Sarstedt</td>
			<td>86.1562.050</td>
			<td>Streaking colonies onto agar plates</td>
		</tr>
		<tr>
			<td>Inoculation spreader</td>
			<td>Sarstedt</td>
			<td>86.1569.005</td>
			<td>Spreading of culture onto agar plates</td>
		</tr>
		<tr>
			<td>Lysogeny broth (LB) broth, Lennox</td>
			<td>Fisher</td>
			<td>BP1427</td>
			<td>Liquid growth media (20 g/L: 5 g/L sodium chloride, 10 g/L tryptone, 5 g/L yeast extract)</td>
		</tr>
		<tr>
			<td>Microfuge</td>
			<td>Fisher</td>
			<td>75002431</td>
			<td>Sorvall Legend Micro 17 for centrifugation of samples</td>
		</tr>
		<tr>
			<td>Mini-centrifuge</td>
			<td>Fisher</td>
			<td>S67601B</td>
			<td>Centrifugation of 0.2 mL PCR tubes</td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>SPL Life Sciences</td>
			<td>10090</td>
			<td>For solid growth media (agar plates): 90 x 15 mm</td>
		</tr>
		<tr>
			<td>Pipettes&#160;</td>
			<td>Mandel</td>
			<td>Various</td>
			<td>Gilson single channel pipettes (P10, P20, P200, P1000)</td>
		</tr>
		<tr>
			<td>Power supply</td>
			<td>Biorad</td>
			<td>1645050</td>
			<td>PowerPac Basic power supply for electrophoresis</td>
		</tr>
		<tr>
			<td>Primers</td>
			<td>IDT</td>
			<td>NA</td>
			<td>PCR reaction component; specific to gene of interest; prepared at 100 &#956;M as directed on the product specification sheet</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>BioBasic</td>
			<td>SB0498</td>
			<td>For the preparation of counterselective media for removal of the pFLP2ab plasmid from transformed A. baumannii</td>
		</tr>
		<tr>
			<td>Taq DNA polymerase</td>
			<td>FroggaBio</td>
			<td>T-500</td>
			<td>PCR reaction component; polymerase supplied with a 10x buffer</td>
		</tr>
		<tr>
			<td>Thermal cycler</td>
			<td>Biorad</td>
			<td>1861096</td>
			<td>Model T100 for PCR</td>
		</tr>
		<tr>
			<td>Toothpicks</td>
			<td>Fisher</td>
			<td>S24559</td>
			<td>For patching colonies onto agar plates</td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td>Agarose gel running buffer component</td>
		</tr>
		<tr>
			<td>Ultrapure water</td>
			<td>Millipore Sigma</td>
			<td>ZLXLSD51040</td>
			<td>MilliQ water purification system: ultra pure water for media and solution preparation, and cell washing</td>
		</tr>
		<tr>
			<td>Wide range DNA marker</td>
			<td>Biobasic</td>
			<td>M103R-2</td>
			<td>Size determination of PCR products on an agarose gel</td>
		</tr>
		<tr>
			<td>Wooden inoculating sticks</td>
			<td>Fisher</td>
			<td>29-801-02</td>
			<td>Inoculating cultures with colonies from agar plates</td>
		</tr>
	</tbody>
</table>

characterizing multidrug efflux systems in acinetobacter baumannii using an efflux&#45;deficient bacterial strain and a single&#45;copy gene expression system

Acinetobacter baumannii is recognized as a challenging Gram-negative pathogen due to its widespread resistance to antibiotics. It is crucial to comprehend the mechanisms behind this resistance to design new and effective therapeutic options. Unfortunately, our ability to investigate these mechanisms in A. baumannii is hindered by the paucity of suitable genetic manipulation tools. Here, we describe methods for utilizing a chromosomal mini-Tn7-based system to achieve single-copy gene expression in an A. baumannii strain that lacks functional RND-type efflux mechanisms. Single-copy insertion and inducible efflux pump expression are quite advantageous, as the presence of RND efflux operons on high-copy number plasmids is often poorly tolerated by bacterial cells. Moreover, incorporating recombinant mini-Tn7 expression vectors into the chromosome of a surrogate A. baumannii host with increased efflux sensitivity helps circumvent interference from other efflux pumps. This system is valuable not only for investigating uncharacterized bacterial efflux pumps but also for assessing the effectiveness of potential inhibitors targeting these pumps.

Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux&#45;Deficient Bacterial Strain and a Single&#45;Copy Gene Expression System

The chromosomal insertion procedure takes only 2 h total across 3 days to see a result-colonies growing on a selective agar plate (Figure 1A-C). The expected number of colonies on the transformation plate is strain dependent: one may see 20-30 or even hundreds of colonies as insertion of Tn7 at attTn7 sites is specific and efficient9. Patching transformation plate colonies onto selective media (Figure 4A<...

Watch this Scientific Journal Video about Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System at JoVE.com

Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux&#45;Deficient Bacterial Strain and a Single&#45;Copy Gene Expression System

We describe a facile procedure for the single-copy chromosomal complementation of an efflux pump gene using a mini-Tn7-based expression system into an engineered efflux-deficient strain of Acinetobacter baumannii. This precise genetic tool allows for controlled gene expression, which is key for the characterization of efflux pumps in multidrug resistant pathogens.

Acinetobacter baumannii is recognized as a challenging Gram-negative pathogen due to its widespread resistance to antibiotics. It is crucial to comprehend ...

We study multi-drug resistance efflux systems in gram-negative bacteria. We are interested in learning about the natural functions of these pumps and how these pumps can be used as a potential drug target. Expression of multi-drug resistance efflux systems is tightly regulated, making it difficult to study their functions.Thus, an expression system that bypasses the regulatory system can be quite useful in the characterization of these pumps. This protocol allows for the expression of genes at levels usually seen in natural settings. Thus, the activity of the gene products mimics what is observed in nature.