Nokea
Bacteria that prefer high levels of salt in their growing environment are referred to as:
- A. calciphiles
- B. halophiles
- C. osmophiles
- D. mesophiles
Correct Answer: B
Rationale: The correct answer is B: halophiles. Halophiles are bacteria that thrive in high salt environments. They have adapted to survive and grow in areas with high salt concentrations. This preference for high salt levels is what distinguishes halophiles from other types of bacteria.
A: Calciphiles are bacteria that prefer high levels of calcium.
C: Osmophiles are bacteria that thrive in environments with high sugar concentrations.
D: Mesophiles are bacteria that prefer moderate temperature ranges for growth.
In summary, the correct term for bacteria that prefer high levels of salt in their growing environment is halophiles, making choices A, C, and D incorrect in this context.
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A relationship in which two organisms benefit is referred to as __________.
- A. commensalism
- B. mutualism
- C. parasitism
- D. competition
Correct Answer: B
Rationale: The correct answer is B: mutualism. In mutualism, both organisms benefit from the relationship. This is because they provide each other with resources or services that help both parties. In contrast, commensalism (A) is a relationship where one organism benefits while the other is neither helped nor harmed. Parasitism (C) is a relationship where one organism benefits at the expense of the other. Competition (D) is a relationship where both organisms are negatively affected as they compete for limited resources. Therefore, mutualism is the correct answer as it describes a mutually beneficial relationship between two organisms.
Which of the following bacteria is known for producing a neurotoxin that causes paralysis?
- A. Clostridium botulinum
- B. Clostridium perfringens
- C. Escherichia coli
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the botulinum neurotoxin, which causes paralysis by blocking the release of acetylcholine at neuromuscular junctions. Clostridium perfringens causes gas gangrene, not paralysis. Escherichia coli is associated with gastrointestinal infections, not paralysis. Staphylococcus aureus produces enterotoxins causing food poisoning, not paralysis. Therefore, Clostridium botulinum is the correct choice based on its well-known association with paralysis due to botulinum neurotoxin production.
A patient with diarrhea had stool culture revealing non-lactose-fermenting, Gram-negative rods. The bacteria produced gas in a nutrient broth. What is the most likely causative agent?
- A. Salmonella typhi
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: D
Rationale: The correct answer is D: Proteus vulgaris. Non-lactose-fermenting, Gram-negative rods that produce gas in a nutrient broth are characteristic of Proteus species. Proteus vulgaris is known for its swarming motility and ability to produce hydrogen sulfide gas. Salmonella typhi and Shigella dysenteriae are Enterobacteriaceae that do not produce gas in a nutrient broth. Escherichia coli is a lactose-fermenting bacterium and would not be expected to produce gas in a nutrient broth.
Gram (+) bacteria ... MG-ribonucleate and Mg. deoxyribonucleate in:
- A. Proportion 4:1
- B. Proportion 2:1
- C. Proportion 8:1
- D. Proportion 1:1
Correct Answer: A
Rationale: The correct answer is A, proportion 4:1. Gram (+) bacteria have a higher ratio of MG-ribonucleate to Mg. deoxyribonucleate because ribosomal RNA is more abundant in actively growing bacterial cells. This higher proportion of MG-ribonucleate to Mg. deoxyribonucleate is essential for protein synthesis and growth. The other choices are incorrect because they do not reflect the higher ratio of ribosomal RNA to DNA in Gram (+) bacteria, which is crucial for their metabolic activities and cellular functions.
Examination of duodenal contents revealed some pyriform protozoa with twin nuclei and four pairs of flagella. There were two supporting filaments between the nuclei and a suctorial disc on the ventral side. What representative of protozoa was revealed in this patient?
- A. Lamblia
- B. Toxoplasma
- C. Leishmania
- D. Intestinal trichomonad
Correct Answer: D
Rationale: The correct answer is D: Intestinal trichomonad. This protozoan matches the description provided, with pyriform shape, twin nuclei, four pairs of flagella, supporting filaments, and a suctorial disc. Lamblia (A) lacks flagella and supporting filaments. Toxoplasma (B) is an intracellular parasite with different morphology. Leishmania (C) belongs to a different class with no flagella or supporting filaments. In summary, the unique combination of features described in the question points to an intestinal trichomonad, making it the correct answer.