Antibiotic production by Brevibacillus (Bacillus) brevis — This organism is exploited commercially to produce which of the following peptide antibiotics?
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Agramicidin A
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Btyrothricin(bacitracin tyrocidin complex)
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Ctyrocidin
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Dall of the above
Answer
Correct Answer: all of the above
Explanation
Introduction / Context:Bacillus brevis (now Brevibacillus brevis) is historically important in antibiotic discovery. It produces several membrane-active peptides used as topical agents and research tools. Recognizing these products aids in linking microbial taxonomy to natural product chemistry.
Given Data / Assumptions:
- Tyrothricin is a mixture of tyrocidines and gramicidins.
- Gramicidin A and tyrocidin are classic products from B. brevis.
- The question asks whether one or all apply.
Concept / Approach:Since B. brevis produces both gramicidin (notably gramicidin A) and tyrocidin, and tyrothricin refers to the combined preparation, the most inclusive correct choice is “all of the above.”
Step-by-Step Solution:
Identify gramicidin A as a linear peptide ionophore from B. brevis.Recognize tyrocidin as a cyclic decapeptide from the same organism.Recall tyrothricin is a mixture (gramicidin + tyrocidin), historically obtained from B. brevis.Verification / Alternative check:Classic antibiotic catalogs and microbiology texts attribute these peptides to B. brevis.
Why Other Options Are Wrong:They are not wrong individually, but each is incomplete relative to the full set the organism produces.
Common Pitfalls:Confusing tyrothricin with bacitracin; bacitracin is from B. subtilis group, whereas tyrothricin is the B. brevis mixture of tyrocidin and gramicidin.
Final Answer:all of the above