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Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus
Published on: March 10, 2017
Extracellular DNA released by glycine-auxotrophic Staphylococcus epidermidis small colony variant facilitates
Junlan Liu1, Zhen Shen1, Jin Tang2
1Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China.
Abstract:
Though a definitive link between small colony variants (SCVs) and implant-related staphylococcal infections has been well-established, the specific underlying mechanism remains an ill-explored field. The present study analyzes the role SCVs play in catheter infection by performing genomic and metabolic analyses, as well as analyzing biofilm formation and impacts of glycine on growth and peptidoglycan-linking rate, on a clinically typical Staphylococcus epidermidis case harboring stable SCV, normal counterpart (NC) and nonstable SCV. Our findings reveal that S. epidermidis stable SCV carries mutations involved in various metabolic processes. Metabolome analyses demonstrate that two biosynthetic pathways are apparently disturbed in SCV. One is glycine biosynthesis, which contributes to remarkable glycine shortage, and supplementation of glycine restores growth and peptidoglycan-linking rate of SCV. The other is overflow of pyruvic acid and acetyl-CoA, leading to excessive acetate. SCV demonstrates higher biofilm-forming ability due to rapid autolysis and subsequent eDNA release. Despite a remarkable decline in cell viability, SCV can facilitate in vitro biofilm formation and in vivo survival of NC when co-infected with its normal counterparts. This work illustrates an intriguing strategy utilized by a glycine-auxotrophic clinical S. epidermidis SCV isolate to facilitate biofilm-related infections, and casts a new light on the role of SCV in persistent infections.
Insights
Small colony variants (SCVs) in Staphylococcus epidermidis infections are linked to biofilm formation. Glycine supplementation restores SCV growth, revealing a strategy for persistent, implant-related infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Biochemistry
Background:
- Small colony variants (SCVs) are linked to persistent Staphylococcus epidermidis infections, particularly those involving medical implants.
- The precise mechanisms by which SCVs contribute to infection pathogenesis remain incompletely understood.
Purpose of the Study:
- To elucidate the role of SCVs in catheter-related Staphylococcus epidermidis infections.
- To investigate the genomic, metabolic, and biofilm-forming characteristics of a clinical SCV isolate and its normal counterpart (NC).
Main Methods:
- Genomic and metabolomic analyses were performed on stable SCV, non-stable SCV, and normal counterpart (NC) strains of Staphylococcus epidermidis.
- Biofilm formation assays were conducted.
- The impact of glycine supplementation on SCV growth and peptidoglycan linking was assessed.
Main Results:
- Stable SCVs exhibited mutations affecting metabolic pathways, notably glycine biosynthesis, leading to glycine auxotrophy.
- SCVs showed enhanced biofilm formation due to increased autolysis and extracellular DNA (eDNA) release.
- Glycine supplementation rescued SCV growth and peptidoglycan linking.
- SCVs promoted in vitro biofilm formation and in vivo survival of NC strains during co-infection.
Conclusions:
- Clinical Staphylococcus epidermidis SCVs employ a strategy involving glycine auxotrophy and enhanced biofilm formation to facilitate persistent, implant-related infections.
- SCVs play a crucial role in establishing and maintaining staphylococcal infections, even with reduced viability.
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