Related Experiment Video
Updated: Aug 9, 2026
06:06
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Competence of pneumococcal isolates and bacterial transformations in man
1Department of Microbiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Infection and Immunity
|November 1, 1972
Summary
Pneumococci transformation occurs in vitro and potentially in natural environments. Capsule presence does not prevent transformation, suggesting other factors are involved in this genetic exchange process.
Area of Science:
- Microbiology
- Genetics
- Bacterial Transformation
Background:
- Bacterial transformation is a mechanism of horizontal gene transfer.
- Streptococcus pneumoniae (pneumococci) are significant human pathogens.
- Understanding transformation competence is crucial for studying bacterial evolution and pathogenicity.
Purpose of the Study:
- To investigate the transformation competence of pneumococci in healthy carriers and patients.
- To determine if bacterial capsules impede transformation.
- To explore the possibility of in vivo bacterial transformation in a natural setting.
Main Methods:
- In vitro transformation assays using soluble deoxyribonucleic acid (DNA).
- Enzymatic hydrolysis of pneumococcal capsules to assess their role in transformation.
- Inoculation of a human pharynx with streptomycin-resistant pneumococci to observe in vivo transformation.
Main Results:
- 25-30% of pneumococcal isolates from carriers and patients were competent for transformation in vitro.
- Hydrolyzing capsules of type 3 and type 8 pneumococci did not restore transformation competence.
- Transformation of type 9 pneumococci was observed in a human carrier after exposure to DNA from streptomycin-resistant donor bacteria.
Conclusions:
- Bacterial capsule presence is not the sole factor preventing transformation in all pneumococcal isolates.
- Natural environments, such as the human pharynx, may support bacterial transformation.
- Horizontal gene transfer in gram-positive cocci could occur in vivo, impacting bacterial adaptation and evolution.
More Related Videos
11:32Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria
Published on: February 23, 2014
06:05Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
Published on: September 30, 2014
Related Concept Videos
01:33Bacterial Transformation
In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
01:33Bacterial Transformation
In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
01:26Transformation
Microbial communities are dynamic environments where cell lysis releases free DNA into the surroundings. Other cells can take up this extracellular DNA through a process known as transformation.When a cell incorporates this foreign DNA into its genome, resulting in genetic modification, the process is known as transformation. Cells capable of this process are termed competent. Competence can be natural, as observed in certain bacteria and archaea, or artificially induced in the...
01:25Mechanism of Antibiotic Resistance in MRSA
Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
01:14Atypical Pneumonia
Atypical pneumonia, often caused by Mycoplasma pneumoniae, is a form of pulmonary infection that differs from the classical presentation of bacterial pneumonia in both its cause and clinical symptoms. Mycoplasma pneumoniae is a pleomorphic bacterium notable for its lack of a rigid cell wall. This structural characteristic imparts resistance to beta-lactam antibiotics and significantly influences the bacterium’s behavior within the human host.Other pathogens responsible for the disease include...
01:26Bacterial Meningitis II: Pathophysiology
Bacterial meningitis typically begins when pathogens such as Neisseria meningitidis and Streptococcus pneumoniae colonize the nasopharynx and invade the bloodstream. This process is facilitated by bacterial virulence factors, such as polysaccharide capsules, which resist phagocytosis and complement-mediated killing. Less commonly, bacteria reach the central nervous system via contiguous spread from infections like otitis media or sinusitis, through congenital or acquired dural defects, or...