Role of the Tet38 Efflux Pump in Staphylococcus aureus Internalization and Survival in Epithelial Cells.
We previously identified the protein Tet38 as a chromosomally encoded efflux pump of Staphylococcus aureus that confers resistance to tetracycline and certain unsaturated fatty acids. Tet38 also contributes to mouse skin colonization. In this study, we discovered a novel regulator of tet38, named tetracycline regulator 21 (TetR21), that bound specifically to the tet38 promoter and repressed pump expression. A ΔtetR21 mutant showed a 5-fold increase in tet38 transcripts and an 8-fold increase in resistance to tetracycline and fatty acids. The global regulator MgrA bound to the tetR21 promoter and indirectly repressed the expression of tet38. To further assess the full role of Tet38 in S. aureus adaptability, we tested its effect on host cell invasion using A549 (lung) and HMEC-1 (heart) cell lines. We used S. aureus RN6390, its Δtet38, ΔtetR21, and ΔmgrA mutants, and a Δtet38 ΔtetR21 double mutant. After 2 h of contact, the Δtet38 mutant was internalized in 6-fold-lower numbers than RN6390 in A549 and HMEC-1 cells, and the ΔtetR21 mutant was internalized in 2-fold-higher numbers than RN6390. A slight increase of 1.5-fold in internalization was found for the ΔmgrA mutant. The growth patterns of RN6390 and the ΔmgrA and ΔtetR21 mutants within A549 cells were similar, while no growth was observed for the Δtet38 mutant. These data indicate that the Tet38 efflux pump is regulated by TetR21 and contributes to the ability of S. aureus to internalize and replicate within epithelial cells.
Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Truong-Bolduc
Massasoit Community College, Brockton, Massachusetts, USA.
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Bolduc
Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Medeiros
Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Vyas
Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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Wang
Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA dhooper@mgh.harvard.edu.
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Hooper
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D050296:Microbial Viability; D011401:Promoter Regions, Genetic; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013752:Tetracycline / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D013752:Tetracycline