microbiology a systems approach test bank

Correct Answer: C

Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during Gram staining. This thick layer is a key characteristic feature that helps differentiate Gram-positive bacteria from Gram-negative bacteria. Rationale: 1. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer. 2. This thick layer provides structural support and protection to the cell. 3. Gram-positive bacteria lack an outer membrane, which is a feature of Gram-negative bacteria (Choice A). 4. Thin peptidoglycan layer is a characteristic of Gram-negative bacteria, not Gram-positive (Choice B). 5. Presence of LPS (lipopolysaccharide) is a feature of Gram-negative bacteria, not Gram-positive (Choice D). In summary, the presence of a thick peptidoglycan layer is a characteristic feature of Gram-positive

Correct Answer: C

Rationale: The correct answer is C: Vibrio. Cholera is caused by Vibrio cholerae bacteria. These bacteria produce a toxin that causes severe diarrhea and dehydration. Escherichia (choice A) and Salmonella (choice B) are known for causing other types of gastrointestinal infections but not cholera. Acinetobacter (choice D) typically causes respiratory infections, not gastrointestinal illnesses like cholera. Therefore, the correct choice is Vibrio as it is specifically associated with cholera.

Correct Answer: A

Rationale: The correct answer is A because enteropathogenic E. coli (EPEC) have fimbrial adhesins that help them bind to enterocytes in the intestines, leading to colonization and infection. This is a key virulence factor of EPEC. Explanation for why other choices are incorrect: B: EPEC typically cause watery diarrhea in infants, not bloody diarrhea similar to shigellosis. C: EPEC are not part of the normal intestinal flora; they are pathogenic bacteria. D: EPEC are not invasive and do not typically produce enterotoxin; they primarily adhere to the intestinal epithelium.

Correct Answer: D

Rationale: The correct answer is D: Blastospores. Blastospores are a type of fungal spore that requires a moist environment to survive. They are commonly found in water bodies like ponds, streams, lakes, and oceans. Mycorrhizae (A) are symbiotic associations between fungi and plant roots, not solely dependent on a moist environment. Armillaria gallica (B) is a type of fungus that can survive in various environmental conditions, not specifically reliant on a moist environment. Choice C is a duplicate of Blastospores, making it incorrect.

Correct Answer: D

Rationale: The correct answer is D: endemic. Endemic refers to a disease that is consistently present in a particular population or region at a relatively stable level. This means the disease is always present in that specific area. Pandemic (A) refers to a disease that spreads across multiple countries or continents. Epidemic (B) refers to a sudden increase in the number of cases of a disease above what is normally expected in that population. Sporadic (C) refers to occasional cases of a disease occurring irregularly in a population. Therefore, the correct choice is D as it specifically describes a disease that is generally present in a given population.