A microbe recovered from an environmental sample grows on a medium composed of agar and a mix of salts. The agar is not digested during incubation. The growth rate increases in high CO2 conditions. The organism is likely a(n)
heterotroph.
autotroph.
chemotroph.
halophile.
The Correct Answer is B
A. Heterotroph: Heterotrophs obtain carbon from organic compounds; if this organism were a heterotroph it would require organic carbon in the medium (or be able to digest agar or other organics), which the description does not indicate.
B. Autotroph: Autotrophs fix carbon dioxide as their carbon source; increased growth under high CO₂ and growth on a mineral salts medium with no digestible organics strongly suggest a CO₂-fixing autotroph.
C. Chemotroph: Chemotrophs obtain energy from chemical compounds rather than light; this term describes energy source rather than carbon source and can overlap with autotrophy or heterotrophy, so the information given points more directly to carbon fixation (autotrophy).
D. Halophile: Halophiles require or tolerate very high salt concentrations for growth; although the medium contains salts, nothing indicates extreme salinity preference, and the CO₂ response points toward autotrophy rather than halophily.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. High osmotic pressure: A hypertonic environment (high external solute concentration) causes water to move out of the cell by osmosis, leading to shrinkage of the cell membrane away from the cell wall (plasmolysis).
B. Protein denaturation: While extreme solute conditions can affect proteins, plasmolysis is primarily driven by osmotic water loss rather than direct denaturation of proteins.
C. DNA mutation: DNA mutation is unrelated to the immediate physical shrinking of the cell that occurs during plasmolysis.
D. Filtration: Filtration is a physical separation method and does not explain why high solute concentrations cause cells to plasmolyze.
Correct Answer is B
Explanation
A. The staff giving the steroid injections did not use proper aseptic technique: Improper aseptic technique at a single clinic could cause local infections, but widespread cases across the U.S. point to a source affecting multiple clinics or batches rather than isolated procedure lapses.
B. The steroid was contaminated at the production plant, so all batches of that drug made at that plant were contaminated with the bacterium: Contamination during manufacture or compounding that led to distribution of contaminated batches nationwide can explain many cases across broad geographic areas and rapid onset after administration.
C. The bacterium is normally on the skin of people, so can easily access the patient's blood during the needle stick: While skin flora can cause infections after injections, Pseudomonas is primarily environmental and widespread patient infections clustered nationally are less consistent with routine skin flora transmission.
D. The needles were re-used and already contaminated before being used on the patients: Reused needles can cause outbreaks but would more likely produce clusters tied to a particular clinic or practitioner rather than many unrelated patients across the country.
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