Transformation in bacteria refers to the uptake of naked DNA from the environment. Among pathogenic bacteria, natural competence for genetic transformation is a key mechanism of antibiotic resistance dissemination. Which organism is classically used to demonstrate transformation and is naturally competent?
- A Escherichia coli — F factor transfer demonstrates transformation between donor and recipient cells
- B Streptococcus pneumoniae — Griffith's experiment (1928) demonstrated transformation of non-virulent R strain to virulent S strain ✓
- C Staphylococcus aureus — plasmid-mediated resistance transfer via transformation
- D Clostridium perfringens — spore germination triggers competence for environmental DNA uptake
Explanation
Streptococcus pneumoniae is the organism in Griffith's classic transformation experiment (1928). Griffith observed that heat-killed virulent S (smooth, encapsulated) strain mixed with live non-virulent R (rough) strain transformed R cells into live virulent S cells. This proved that a 'transforming principle' could transfer genetic information. The transforming principle was later identified as DNA by Avery, MacLeod, and McCarty (1944). S. pneumoniae is naturally competent due to its competence stimulating peptide (CSP) system. The natural competence of pneumococci is clinically relevant because it allows horizontal transfer of penicillin-binding protein genes (pbp1a, pbp2b, pbp2x) from related streptococci, generating mosaic PBPs that reduce penicillin affinity — a key mechanism of pneumococcal penicillin resistance.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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