Normally a commensal in the human intestine, this bacterium became pathogenic after acquiring a toxin gene from a Shigella bacterium.

Verified step by step guidance

1. Identify the bacterium that is normally a commensal in the human intestine. Common examples include Escherichia coli (E. coli).
2. Understand the concept of horizontal gene transfer, which is the movement of genetic material between organisms other than through vertical transmission (from parent to offspring).
3. Recognize that the bacterium acquired a toxin gene from Shigella, a process that can occur through mechanisms such as transformation, transduction, or conjugation.
4. Consider how the acquisition of a toxin gene can transform a commensal bacterium into a pathogenic one, as the new gene may encode for a virulence factor that causes disease.
5. Reflect on the implications of such genetic changes in bacteria, including the potential for increased virulence and the challenges it poses for treatment and prevention of infections.

Key Concepts

Commensal Bacteria

Commensal bacteria are microorganisms that normally inhabit the human body without causing harm. They play essential roles in maintaining gut health, aiding digestion, and protecting against pathogenic organisms. Understanding the balance between commensal and pathogenic bacteria is crucial for comprehending how certain bacteria can shift from harmless to harmful.

Horizontal Gene Transfer

Horizontal gene transfer is the process by which bacteria can exchange genetic material, including toxin genes, with one another. This mechanism allows for rapid adaptation and evolution, enabling commensal bacteria to acquire virulence factors from pathogenic strains, such as Shigella. This concept is vital for understanding how non-pathogenic bacteria can become pathogenic.

Pathogenicity

Pathogenicity refers to the ability of an organism to cause disease. It is determined by various factors, including the presence of virulence factors like toxins, which can disrupt host cellular functions. In the context of the question, the acquisition of a toxin gene transforms a normally harmless bacterium into a potential pathogen, highlighting the dynamic nature of microbial interactions.