If an archaeal species thrives in a pool containing 0.01 M HCl(aq), which term best describes this organism?

• A. Acidophile
• B. Methanogen
• C. Thermophile
• D. Halophile

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the environmental condition described. The pool contains 0.01 M HCl, which means it is acidic due to the presence of hydrochloric acid.
2. Step 2: Recall the definitions of the terms: - Acidophile: an organism that thrives in acidic environments (low pH). - Methanogen: an organism that produces methane, typically anaerobic archaea. - Thermophile: an organism that thrives at high temperatures. - Halophile: an organism that thrives in high salt concentrations.
3. Step 3: Determine the pH of the environment. Since HCl is a strong acid, 0.01 M HCl corresponds to a pH of approximately 2 (pH = -\log_{10}[H^+]).
4. Step 4: Match the organism's preferred environment to the options. Because the environment is acidic (low pH), the organism that thrives here is best described as an acidophile.
5. Step 5: Conclude that the term 'acidophile' best fits an archaeal species thriving in 0.01 M HCl, as it indicates adaptation to acidic conditions.