In 1928, Fred Griffith, a British pathologist was studying the pathogenicity of pneumococcal infections in mice that also causes pneumonia in humans. Based on the disease response, pneumococcal strains could be classified as virulent or disease-causing and avirulent or non-pathogenic. He observed that the virulent strains of the causative organism, Pneumococcus (Streptococcus) pneumoniae can be easily distinguished from the avirulent ones by the fact that they produced smooth glistening colonies on agar surfaces and thus were referred to as S strains. Several such S strains could be identified based on a polysaccharide capsule that carries antigenic properties. Such strains were labeled as SI, SII, SIII, etc., basically differing in the composition of their capsular polysaccharides, and thus, eliciting different antigenic responses.


Transformation Frequency Competence Development Deoxyribose Nucleic Acid Type Bacterium Autolytic Enzyme 
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Further Readings

  1. Avery OT, Macleod CM, McCarty M (1944) Studies on the chemical nature of the substance inducing transformation of pneumococcal types. I. Induction of transformation by a deoxyribonucleic acid fraction isolated from pneumococcus type III. J Exp Med 79:137–158PubMedCrossRefGoogle Scholar
  2. Bergmans HE, van Die IM, Hoekstra WP (1981) Transformation in Escherichia coli: stages in the process. J Bacteriol 146(2):564–570PubMedGoogle Scholar
  3. Campbell EA, Choi SY, Masure HR (1998) A competence regulon in Streptococcus pneumoniae revealed by genomic analysis. Mol Microbiol 27:929–939PubMedCrossRefGoogle Scholar
  4. Chen I, Dubnau D (2004) DNA uptake during bacterial transformation. Nat Rev Micrbiol 2:241–249CrossRefGoogle Scholar
  5. Etchuuya R, Ito M, Kitano S, Shigi F, Sobue R, Maeda S (2011) A novel type of natural transformation involving cell-derived DNA and a putative promoting pheromone. PLoS ONE 6(1):e16355PubMedCrossRefGoogle Scholar
  6. Kaufenstein M, van der Laan M, Graumann PL (2011) The three layered DNA uptake machinery at the cell pole in competent Bacillus subtilis cells is a stable complex. J Bacteriol 193(7):1633–1642PubMedCrossRefGoogle Scholar
  7. Lacks SA (2003) Rambling and scrambling in bacterial transformation—a historical and personal memoir. J Bacteriol 185(1):1–6PubMedCrossRefGoogle Scholar
  8. Lorenz MG, Wackemagel W (1994) Bacterial gene transfer by natural genetic transformation in the environment. Microbiol Rev 58(3):563–602PubMedGoogle Scholar
  9. Mercenier A, Chassy BM (1988) Strategies for the development of bacterial transformation systems. Biochimi 70(4):503–517CrossRefGoogle Scholar
  10. Petersen FC, Tao L, Scheie AA (2005) DNA binding-uptake system: a link between cell-to-cell communication and biofilm formation. J Bacteriol 187(13):4392–4400PubMedCrossRefGoogle Scholar
  11. Radfield RJ, Schrag MR, Dean AM (1997) The evolution of bacterial transformation: sex with poor relations. Genetics 146:27–38Google Scholar
  12. Steinmoen H, Knusten E, Havarstein LS (2002) Induction of natural competence in Streptococcus pneumoniae triggers lysis and DNA release from a subfraction of cell population. Proc Natl Acad Sci U S A 99:7681–7686PubMedCrossRefGoogle Scholar
  13. Wirth R, Friesenegger A, Fiedler S (1989) Transformation of various species of gram-negative bacteria belonging to 11 different genera by electroporation. Mol Gen Genet 216:175–177PubMedCrossRefGoogle Scholar

Copyright information

© Springer India 2013

Authors and Affiliations

  1. 1.Department of GeneticsUniversity of Delhi, South CampusNew DelhiIndia

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