| 1. |
- Le, Nguyen-Hung, et al.
(författare)
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Killing of Gram-negative and Gram-positive bacteria by a bifunctional cell wall-targeting T6SS effector
- 2021
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Science. - 0027-8424 .- 1091-6490. ; 118:40
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Tidskriftsartikel (refereegranskat)abstract
- The type VI secretion system (T6SS) is a powerful tool deployed by Gram-negative bacteria to antagonize neighboring organisms. Here, we report that Acinetobacter baumannii ATCC 17978 (Ab17978) secretes D-lysine (D-Lys), increasing the extracellular pH and enhancing the peptidoglycanase activity of the T6SS effector Tse4. This synergistic effect of D-Lys on Tse4 activity enables Ab17978 to out-compete Gram-negative bacterial competitors, demonstrating that bacteria can modify their microenvironment to increase their fitness during bacterial warfare. Remarkably, this lethal combination also results in T6SS-mediated killing of Gram-positive bacteria. Further characterization revealed that Tse4 is a bifunctional enzyme consisting of both lytic transglycosylase and endopeptidase activities, thus representing a family of modularly organized T6SS peptidoglycan-degrading effectors with an unprecedented impact in antagonistic bacterial interactions.
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| 2. |
- Le, Nguyen-Hung, et al.
(författare)
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Peptidoglycan editing provides immunity to Acinetobacter baumannii during bacterial warfare
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 6:30
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Tidskriftsartikel (refereegranskat)abstract
- Peptidoglycan (PG) is essential in most bacteria. Thus, it is often targeted by various assaults, including interbacterial attacks via the type VI secretion system (T6SS). Here, we report that the Gram-negative bacterium Acinetobacter baumannii strain ATCC 17978 produces, secretes, and incorporates the noncanonical D-amino acid D-lysine into its PG during stationary phase. We show that PG editing increases the competitiveness of A. baumannii during bacterial warfare by providing immunity against peptidoglycan-targeting T6SS effectors from various bacterial competitors. In contrast, we found that D-Lys production is detrimental to pathogenesis due, at least in part, to the activity of the human enzyme d-amino acid oxidase (DAO), which degrades D-Lys producing H2O2 toxic to bacteria. Phylogenetic analyses indicate that the last common ancestor of A. baumannii had the ability to produce D-Lys. However, this trait was independently lost multiple times, likely reflecting the evolution of A. baumannii as a human pathogen.
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