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Mutation of the Carboxy-Terminal Processing Protease in Acinetobacter baumannii Affects Motility, Leads to Loss of Membrane Integrity, and Reduces Virulence

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Institute of Medical Sciences, Tzu Chi University, Hualien 97004, Taiwan
2
Institute of Medical Biotechnology, Tzu Chi University, Hualien 97004, Taiwan
3
Department of Molecular Biology and Human Genetics, Tzu Chi University, Hualien 97004, Taiwan
4
Department of Microbiology, School of Medicine, Tzu Chi University, Hualien 97004, Taiwan
*
Author to whom correspondence should be addressed.
Pathogens 2020, 9(5), 322; https://doi.org/10.3390/pathogens9050322
Received: 26 March 2020 / Revised: 13 April 2020 / Accepted: 24 April 2020 / Published: 26 April 2020
(This article belongs to the Section Human Pathogens)
Motility plays an essential role in the host–parasite relationship of pathogenic bacteria, and is often associated with virulence. While many pathogenic bacteria use flagella for locomotion, Acinetobacter baumannii strains do not have flagella, but have other features that aid in their motility. To study the genes involved in motility, transposon mutagenesis was performed to construct A. baumannii mutant strains. Mutant strain MR14 was found to have reduced motility, compared to wild-type ATCC 17978. NCBI BLAST analysis revealed that the Tn10 transposon in the MR14 genome is integrated into the gene that encodes for carboxy-terminal processing protease (Ctp). Additionally, MR14 exhibits a mucoidy, sticky phenotype as the result of increased extracellular DNA (eDNA) caused by bacterial autolysis. Transmission and scanning electron microscopy revealed cytoplasmic content leaving the cell and multiple cell membrane depressions, respectively. MR14 showed higher sensitivity to environmental stressors. Mutation of the ctp gene reduced invasion and adhesion of A. baumannii to airway epithelial cells, potentially due to increased hydrophobicity. In the zebrafish model of infection, MR14 increased the survival rate by 40% compared to the wild-type. Taken together, the ctp gene in A. baumannii has a pivotal role in maintaining membrane integrity, adaptation to environmental stress, and controlling virulence. View Full-Text
Keywords: Acinetobacter baumannii; Tn10 transposon; carboxy-terminal processing protease (Ctp); motility; mucoidy; adhesion; invasion Acinetobacter baumannii; Tn10 transposon; carboxy-terminal processing protease (Ctp); motility; mucoidy; adhesion; invasion
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Roy, R.; You, R.-I.; Lin, M.-D.; Lin, N.-T. Mutation of the Carboxy-Terminal Processing Protease in Acinetobacter baumannii Affects Motility, Leads to Loss of Membrane Integrity, and Reduces Virulence. Pathogens 2020, 9, 322.

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