Cited by 94Antimicrobial Resistance in StaphylococcusBacterial Genetics and BiotechnologyBacterial biofilms and quorum sensing

Molecular analysis of the thymidine-auxotrophic small colony variant phenotype of Staphylococcus aureus

Besier, Silke, Ludwig, Albrecht, Ohlsen, Knut, Brade, Volker, Wichelhaus, Thomas A.·2007·International Journal of Medical Microbiology

Abstract

Thymidine-auxotrophic small colony variants (SCVs) of Staphylococcus aureus are frequently isolated from the chronically infected airways of patients suffering from cystic fibrosis. To date, little is known regarding the molecular mechanisms leading to the formation of this special phenotype, but the auxotrophism for thymidine suggests that impaired thymidine metabolism might play a major role. Sequence analysis of the thymidylate synthase-encoding thyA gene of six clinical thymidine-auxotrophic S. aureus SCVs revealed that all isolates had mutations within thyA. In five isolates the function of the thymidylate synthase was definitely impaired: three of them showed a truncation of the thyA coding sequence by nonsense or frame-shift mutations, in one further isolate the active site of the enzyme was affected by an internal 12-bp deletion, and another isolate had a 173-bp deletion spanning the 5'-terminal region of thyA and the preceding DNA sequence. The sixth isolate showed two amino acid substitutions within the thyA gene product. To confirm the importance of impaired thymidylate synthase synthesis or activity for the formation of the thymidine-auxotrophic SCV phenotype, we constructed a thyA knock-out mutant of a wild-type S. aureus strain. This mutant showed all characteristics of clinical SCVs, such as slow growth, decreased pigment production, reduced hemolytic activity, auxotrophism for thymidine, resistance to trimethoprim/sulfamethoxazol, and reduced plasma coagulase activity. Complementation of the thyA knock-out mutant with intact thyA in trans nearly restored the normal phenotype. In conclusion, these data confirm at the molecular level that impaired thymidylate synthase function is causative for the formation of the thymidine-auxotrophic SCV phenotype in S. aureus.

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Crossref · 10.1016/j.ijmm.2007.02.003

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Authors
Besier, S., Ludwig, A., Ohlsen, K., Brade, V., & Wichelhaus, T. A.
Affiliations
  • Goethe University Frankfurt (DE)
  • University of Würzburg (DE)
Corresponding author
Besier, Silke
Venue
International Journal of Medical Microbiology
Publisher
Elsevier BV
Published
2007-07
Volume
297
Issue
4
Pages
217-225
ISSN
1438-4221 (ISSN-L)
OpenAlex
W2055046588
Cited by
94
References
30
Citations by year
2026: 1 · 2025: 2 · 2024: 7 · 2023: 6 · 2022: 6 · 2021: 4 · 2020: 5 · 2019: 3 · 2018: 5 · 2017: 7 · 2016: 4 · 2015: 10 · 2014: 4 · 2013: 6 · 2012: 2
FWCI
3.36
Type
journal article
Language
en
Open access
closed
Locations
  • International Journal of Medical Microbiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Infectious Diseases › Antimicrobial Resistance in Staphylococcus
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Bacterial Genetics and Biotechnology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Bacterial biofilms and quorum sensing
Keywords
Staphylococcus aureus, small colony variants, thymidine auxotrophy, thymidylate synthase, cystic fibrosis, thymidine metabolism, complementation, trimethoprim-sulfamethoxazole resistance, hemolytic activity, pigment production
MeSH terms
Genetic Complementation Test, Humans, Mutation, Phenotype, Staphylococcus aureus, Thymidine, Trimethoprim, Sulfamethoxazole Drug Combination

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