To grow a newly discovered microbe in the lab, you realize that you must supplement the media with tyrosine, a required amino acid. One can assume the organism is ____________________________

Question

To grow a newly discovered microbe in the lab, you realize that you must supplement the media with tyrosine, a required amino acid.  One can assume the organism is ____________________________

BlackTom AI · Accepted Answer

An organism that cannot synthesize tyrosine and therefore requires it supplied in the growth medium is called an auxotroph.

1. Identify and explain the relevant knowledge points and concepts
- Prototroph vs auxotroph: a prototroph can synthesize all compounds needed for growth from basic nutrients; an auxotroph has lost the ability to synthesize one or more essential metabolites (e.g., an amino acid) and therefore requires that compound to be added to the medium.
- Minimal (defined) medium contains basic salts and a carbon source but not complex growth factors; supplemented media supply specific amino acids, vitamins, or cofactors.
- Genetic basis: auxotrophy usually results from mutations in a biosynthetic pathway (e.g., enzymes required to make tyrosine).

2. Step-by-step reasoning process
- Observation: the newly discovered microbe only grows in the lab when tyrosine is added to the medium.
- Interpretation: growth dependence on an externally supplied tyrosine indicates the organism cannot make tyrosine itself.
- Conclusion: inability to synthesize an essential metabolite (tyrosine) defines an auxotrophic phenotype for that metabolite.

3. Calculations / intermediate steps
- No numerical calculations are required. The logical intermediate step is: growth + tyrosine supplement → endogenous biosynthesis absent → auxotroph.

4. Why the correct answer is correct
- "An auxotroph" precisely names an organism that requires supplementation of a specific metabolite (here, tyrosine) because it cannot synthesize it. This matches the experimental observation.

5. Why the other options are incorrect
- "Lacking ribosomes": absence of ribosomes would prevent all protein synthesis and make growth impossible regardless of tyrosine supplementation.
- "Lacking the Kreb's cycle": impairment of the Krebs (TCA) cycle affects energy metabolism broadly; supplementing tyrosine would not restore central energy production and would not specifically rescue growth.
- "Anaerobic": being anaerobic means growth does not require oxygen; this has nothing to do with requiring a particular amino acid like tyrosine.

6. Conclusion confirming the final answer
- Therefore the organism is an auxotroph, which matches the provided correct answer: an auxotroph.

To grow a newly discovered microbe in the lab, you realize that you must supplement the media with tyrosine, a required amino acid. One can assume the organism is ____________________________单项选择题

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