In Griffith's classical experiments on transformation, which of the following scenarios led to a dead mouse? Select all that apply. (NCLEX/HESI/TEAS)
a. Infecting the mouse with a living strain of S. pneumoniae that makes a capsule
b. Infecting the mouse with a heat-killed strain of S. pneumoniae that makes a capsule
c. Infecting the mouse with a heat-killed strain of S. pneumoniae that makes a capsule and a living strain of S. pneumoniae that cannot make a capsule
d. Infecting the mouse with a living strain of S. pneumoniae that cannot make a capsule

Verified step by step guidance

1. Understand the concept of transformation: Griffith's experiments demonstrated that genetic material could be transferred from one bacterium to another, transforming the recipient bacterium.
2. Identify the role of the capsule: The capsule is a protective layer that allows S. pneumoniae to evade the host's immune system, making it virulent.
3. Analyze scenario a: A living strain with a capsule is virulent and can cause disease, leading to a dead mouse.
4. Analyze scenario b: A heat-killed strain with a capsule is non-virulent because the bacteria are dead and cannot cause disease, leading to a live mouse.
5. Analyze scenario c: The heat-killed strain with a capsule can transfer genetic material to the living non-capsulated strain, transforming it into a virulent form, leading to a dead mouse.

Key Concepts

Transformation

Transformation is a process in microbiology where a bacterium takes up foreign DNA from its environment, leading to genetic changes. In Griffith's experiments, this phenomenon was demonstrated when non-virulent strains of Streptococcus pneumoniae became virulent after acquiring DNA from heat-killed virulent strains, illustrating how genetic material can influence bacterial characteristics.

Virulence Factors

Virulence factors are traits of a microorganism that enhance its ability to cause disease. In the context of S. pneumoniae, the presence of a capsule is a critical virulence factor that helps the bacteria evade the host's immune system. Understanding which strains possess this factor is essential for predicting the outcomes of infections in Griffith's experiments.

Experimental Controls

Experimental controls are essential in scientific experiments to ensure that the results are due to the variable being tested. In Griffith's experiments, controls included using heat-killed bacteria and non-virulent strains to compare against virulent strains. Recognizing the role of these controls helps in understanding how different combinations of bacterial strains affected the health of the mice.