The cleanup of various industrial wastes by living organisms is referred to as __________.

Correct Answer: C

Rationale: The correct answer is C: bioremediation. Bioremediation is the process of using living organisms to clean up environmental pollution, including industrial wastes. This method utilizes microorganisms, plants, or fungi to break down or neutralize pollutants. Biomining (A) is the process of extracting valuable metals from ores using biological organisms. Biosynthesis (B) refers to the production of complex molecules by living organisms. Bioengineering (D) involves the application of engineering principles to biological systems, not specifically related to cleaning up industrial wastes. Therefore, the most appropriate term for the cleanup of industrial wastes by living organisms is bioremediation.

Correct Answer: C

Rationale: The correct answer is C: Microaerophiles. These bacteria grow best in environments with low oxygen levels. They require oxygen for respiration but at lower concentrations than what is present in the atmosphere. This allows them to thrive in conditions where oxygen is limited but not completely absent. A: Facultative anaerobes can grow in both the presence and absence of oxygen. B: Obligate aerobes require oxygen for growth. D: Obligate anaerobes cannot survive in the presence of oxygen and typically grow in anaerobic environments. In summary, microaerophiles are the correct choice as they specifically thrive in low oxygen environments, distinguishing them from the other options.

Correct Answer: B

Rationale: The correct answer is B, Streptococcus pneumoniae. This bacterium is the classic causative agent of croupous pneumonia due to its ability to infect the lungs and cause inflammation. Streptococcus pneumoniae is a common pathogen known for causing pneumonia in both adults and children. It is characterized by the presence of a capsule that helps it evade the host immune system. Choice A, Chlamydia pneumoniae, is not the correct answer as it is more commonly associated with atypical pneumonia. Choice C, Mycoplasma pneumoniae, is also associated with atypical pneumonia and not croupous pneumonia. Choice D, Staphylococcus aureus, can cause pneumonia, but it is not the classic causative agent of croupous pneumonia.

Correct Answer: B

Rationale: The correct answer is B: Penicillin. Penicillin is the drug of first choice for treating syphilis due to its effectiveness in eradicating the bacterium Treponema pallidum, which causes syphilis. It is the most reliable treatment with well-established efficacy. Gentamicin (A), ciprofloxacin (C), and chloramphenicol (D) are not recommended for treating syphilis as they are not effective against the specific bacteria causing the infection. Penicillin remains the gold standard for syphilis treatment.

Correct Answer: D

Rationale: The correct answer is D: all of them. Malignant disease weakens the immune system, making individuals more susceptible to infections. Cytostatic therapy suppresses the immune system, increasing the risk of infections. Premature birth can lead to underdeveloped immune systems, making babies more prone to infections. Therefore, all three choices are risk factors for the development of infections. Other choices are incorrect because each individual risk factor listed contributes to an increased susceptibility to infections.

Correct Answer: D

Rationale: The correct answer is D: Trichomonas tenax. Trichomonas tenax is a flagellated protozoan that is commonly found in the oral cavity, specifically in dental plaque. The description provided in the question matches the characteristics of Trichomonas tenax, such as unicellular structure, distinct layers in the cytoplasm, wide pseudopodia, and barely visible core. Entamoeba gingivalis (choice A) and Entamoeba histolytica (choice B) are amoebas, not flagellated protozoa, and they do not exhibit the characteristics described in the question. Lamblia (choice C) is also an incorrect choice as it is a different type of protozoan that does not match the description provided.

Correct Answer: D

Rationale: The correct answer is D: complex. Bacteriophages are considered complex viruses because they have a complex structure consisting of a polyhedral head, a helical tail, and tail fibers. The head contains the viral genetic material, while the tail facilitates attachment to the host bacterial cell. This complexity distinguishes bacteriophages from simpler viruses like helical and icosahedral viruses. Helical viruses have a rod-like shape, while icosahedral viruses have a symmetrical, 20-sided structure. Enveloped viruses have a lipid bilayer envelope surrounding their capsid, which bacteriophages lack. Therefore, the unique and intricate structure of bacteriophages classifies them as complex viruses.

Correct Answer: A

Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria. Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation. Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar. Step 4: Therefore, the correct answer is A: Salmonella. Summary: B: Escherichia coli ferments lactose, producing pink colonies on Endo agar. C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar. D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.

Correct Answer: A

Rationale: Rationale: Shigella dysenteriae produces Shiga toxin, which inhibits protein synthesis by inactivating the 60S ribosomal subunit. This disrupts the translation process, leading to cell death. Escherichia coli (choice B) does not produce a toxin that inhibits protein synthesis. Clostridium tetani (choice C) produces tetanospasmin, which affects the nervous system. Staphylococcus aureus (choice D) produces toxins that cause food poisoning but do not inhibit protein synthesis.