Which of the following statements is false?
a. E. coli never causes disease.
b. E. coli provides vitamin K for its host.
c. E. coli often exists in a mutualistic relationship with humans.
d. A disease-causing strain of E. coli causes bloody diarrhea.

Verified step by step guidance

1. Step 1: Understand the role of E. coli in the human body. E. coli is a common bacterium found in the intestines of humans and animals. It is known for its mutualistic relationship with humans, where it can provide benefits such as vitamin K production.
2. Step 2: Analyze statement a. Consider whether E. coli can cause disease. While many strains are harmless, some strains, like E. coli O157:H7, are pathogenic and can cause diseases such as food poisoning.
3. Step 3: Evaluate statement b. E. coli is known to synthesize vitamin K, which is essential for blood clotting, and this is a well-documented mutualistic benefit.
4. Step 4: Consider statement c. E. coli often exists in a mutualistic relationship with humans, providing benefits like vitamin K production and aiding in digestion.
5. Step 5: Examine statement d. Some strains of E. coli, particularly pathogenic ones, can cause severe symptoms such as bloody diarrhea, indicating that this statement is true.

Key Concepts

E. coli and Human Health

Escherichia coli (E. coli) is a bacterium commonly found in the intestines of humans and animals. While most strains are harmless and play a role in digestion, some can cause serious illnesses. Understanding the dual nature of E. coli is crucial for distinguishing between beneficial and pathogenic strains.

Mutualism in Microbiology

Mutualism is a type of symbiotic relationship where both organisms benefit. In the case of E. coli, it helps synthesize vitamin K, which is essential for blood clotting, while humans provide a nutrient-rich environment for the bacteria. This relationship exemplifies how certain microbes contribute positively to human health.

Pathogenic Strains of E. coli

Certain strains of E. coli, such as Enterohemorrhagic E. coli (EHEC), are pathogenic and can cause severe gastrointestinal diseases, including bloody diarrhea. These pathogenic strains often possess specific virulence factors that enable them to adhere to intestinal cells and produce toxins, leading to illness.