AP-Micro (Microbiology) Microbial Ecology and Pathogenesis 1 — Questions and Answers
Question 1: What is the term for a mutually beneficial relationship between a microorganism and its host?
- Parasitism
- Commensalism
- Mutualism (Correct answer)
- Predation
Correct answer: Mutualism
Mutualism describes a symbiotic relationship where both the microorganism and its host benefit from their interaction. For example, gut bacteria that aid in digestion and nutrient absorption while receiving a stable environment and nutrients from the host exemplify mutualism. This contrasts with parasitism (one benefits, one harmed) or commensalism (one benefits, other unaffected).
Question 2: Which of the following is a key factor in microbial pathogenicity?
- Ability to form endospores
- Presence of ribosomes
- Production of virulence factors (Correct answer)
- Speed of DNA replication
Correct answer: Production of virulence factors
Microbial pathogenicity, the ability of a microbe to cause disease, is primarily determined by its virulence factors. These are molecules produced by pathogens that enable them to colonize the host, evade immune defenses, and cause damage to host tissues. Examples include toxins, adhesins, and enzymes that degrade host components.
Question 3: What role do microbes play in nitrogen cycling in the environment?
- Produce nitrogen gas
- Fix nitrogen into usable forms (Correct answer)
- Release carbon dioxide
- Break down proteins
Correct answer: Fix nitrogen into usable forms
Microbes play a critical role in the nitrogen cycle, particularly in nitrogen fixation. Certain bacteria and archaea convert atmospheric nitrogen gas (N2), which is unusable by most organisms, into ammonia (NH3) or other nitrogenous compounds. This 'fixed' nitrogen is then available for plants and other organisms to synthesize essential biomolecules like proteins and nucleic acids.
Question 4: Which microorganism is most likely to cause an opportunistic infection?
- Escherichia coli (E. coli) in the gut
- Streptococcus pyogenes on the skin
- Candida albicans in immunocompromised patients (Correct answer)
- Mycobacterium tuberculosis in healthy lungs
Correct answer: Candida albicans in immunocompromised patients
An opportunistic infection is caused by pathogens that take advantage of a weakened immune system or a disruption in the normal microbiota. Candida albicans is a yeast that is part of the normal human flora but can cause infections (like thrush or candidiasis) when the host is immunocompromised, such as in HIV patients or those undergoing chemotherapy.
Question 5: What is the first line of defense against microbial pathogens in the human body?
- Antibodies
- White blood cells
- Skin and mucous membranes (Correct answer)
- Fever
Correct answer: Skin and mucous membranes
The skin and mucous membranes constitute the body's first line of defense against microbial pathogens. They act as physical barriers, preventing entry, and also possess chemical defenses like antimicrobial peptides and enzymes. If these barriers are breached, then internal defenses like white blood cells and antibodies come into play.
AP-Micro (Microbiology) Microbial Ecology and Pathogenesis 1
What is the term for a mutually beneficial relationship between a microorganism and its host?