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. 2017 Apr;6(2):e00418.
doi: 10.1002/mbo3.418. Epub 2016 Oct 19.

Multiple roles for a novel RND-type efflux system in Acinetobacter baumannii AB5075

Kyle A Tipton  1 , Marjan Farokhyfar  2 , Philip N Rather  1   2   3
Affiliations

Multiple roles for a novel RND-type efflux system in Acinetobacter baumannii AB5075

Kyle A Tipton et al. Microbiologyopen. 2017 Apr.

Abstract

Colony opacity phase variation in Acinetobacter baumannii strain AB5075 is regulated by a reversible high-frequency switch. Transposon mutagenesis was used to generate mutations that decreased the opaque to translucent switch and a gene encoding a predicted periplasmic membrane fusion component of a resistance-nodulation-cell division (RND)-type efflux system was isolated. This gene was designated arpA and immediately downstream was a gene designated arpB that encodes a predicted membrane transporter of RND-type systems. A nonpolar, in-frame deletion in arpA resulted in a 70-fold decrease in the opaque to translucent switch. An arpB::Tc mutant exhibited a 769-fold decrease in the opaque to translucent switch. However, the translucent to opaque switch was largely unchanged in both the arpA and arpB mutants. The arpA and arpB mutants also exhibited increased surface motility in the opaque form and the arpB mutant exhibited increased susceptibility to aminoglycosides. The arpA and arpB mutants were both attenuated in a Galleria mellonella model of virulence. A divergently transcribed TetR-type regulator ArpR was capable of repressing the arpAB operon when this TetR regulator was overexpressed. The arpR gene was also involved in regulating the opaque to translucent switch as an in-frame arpR mutation decreased this switch by 1,916-fold.

Keywords: Acinetobacter; RND efflux system; phase variation.

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Figures

Figure 1
Figure 1
Decreased phase variation in an arpA mutant. (a) A typical wild‐type opaque colony variant of AB5075 is shown compared to 5075.8B arpA:: EZ‐Tn5 <Tet‐1> after 36 hr of growth on a 0.5× LB, 0.8% agar plate. The mottled appearance at the outside edge of the wild type is due to translucent variants arising within the opaque colony. (b) The organization of the arpAB region and the site of the arpA:: EZ‐Tn5 <Tet‐1> insertion that blocks phase variation is depicted by an arrow. Proteins exhibiting the closest match to ArpA and ArpB are shown below each gene
Figure 2
Figure 2
Surface motility. (a) The motility of opaque (left panel) and translucent (right panel) variants of wild‐type AB5075, the ∆arpA mutant KT2, and arpB::Tc mutant AB00075 are shown after 12 hr of growth on 0.35% Eiken agar plates incubated at 37°C. (b) Quantitation of surface motility. The values shown represent the average of three separate motility assays for each strain. Conditions for the motility assays were the same as shown in A
Figure 3
Figure 3
arpA and arpB mutants exhibit decreased virulence in a Galleria mellonella model. The ability of wild‐type AB5075 and the isogenic ∆arpA and arpB::Tc mutants to kill G. mellonella waxworms is shown on the Kaplan–Meier plots. The data shown represent the average of three independent experiments with a total of 30 worms per strain
Figure 4
Figure 4
Effect of ArpR on arpA expression. The levels of arpA expression were determined by quantitative RT‐PCR and the values shown are relative to the control gene clpX. The values for the left side represent the levels of arpA expression in the arpR mutant relative to wild type. The values on the right side represent the levels of arpA expression in cells overexpressing arpR from a plasmid relative to cells containing the vector alone
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References

    1. Alvarez‐Ortega, C. , Olivares, J. , & Martinez, J. L. (2013). RND multidrug efflux pumps: What are they good for? Frontiers in Microbiology, 4, 7. - PMC - PubMed
    1. Anes, J. , McCusker, M. P. , Fanning, S. , & Martins, M. (2015). The ins and outs of RND efflux pumps in Escherichia coli . Frontiers in Microbiology, 6, 587. - PMC - PubMed
    1. Antunes, L. C. , Visca, P. , & Towner, K. J. (2014). Acinetobacter baumannii: Evolution of a global pathogen. Pathogens and Disease, 71, 292–301. - PubMed
    1. Bergogne‐Berezin, E. , & Towner, K. J. (1996). Acinetobacter spp. as nosocomial pathogens: Microbiological, clinical, and epidemiological features. Clinical Microbiology Reviews, 9, 148–165. - PMC - PubMed
    1. Casadesus, J. , & Low, D. A. (2013). Programmed heterogeneity: Epigenetic mechanisms in bacteria. The Journal of Biological Chemistry, 288, 13929–13935. - PMC - PubMed

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