Herbicide detoxification gene identity — nitrilase is encoded by which bacterial gene source?

Introduction / Context:
Nitrilases are enzymes that hydrolyze nitriles to corresponding acids and ammonia. In plant biotechnology, bacterial nitrilase genes have been used to detoxify specific herbicides (e.g., bromoxynil) by converting them into less harmful products.

Given Data / Assumptions:

• bxn is historically associated with bromoxynil detoxification.
• bar/pat genes encode phosphinothricin acetyltransferase and are unrelated to nitrilase.
• Question seeks the gene that encodes a nitrilase.

Concept / Approach:

The bxn gene, originally described from Klebsiella (commonly reported as Klebsiella pneumoniae or closely related taxa), encodes a nitrilase that degrades bromoxynil. In contrast, the bar (or pat) genes from Streptomyces encode enzymes that detoxify phosphinothricin (glufosinate) by acetylation, not by nitrile hydrolysis.

Step-by-Step Solution:

Verification / Alternative check:

Engineering bromoxynil resistance in crops has employed bxn to confer the ability to degrade the herbicide, consistent with nitrilase activity.

Why Other Options Are Wrong:

bar (and pat) encode phosphinothricin acetyltransferase, not nitrilase; “Both” is incorrect since bar is not a nitrilase gene; “None” is incorrect because bxn is a valid nitrilase gene.

Common Pitfalls:

Confusing herbicide resistance strategies: nitrilase (nitrile hydrolysis) vs. acetyltransferase (glufosinate detoxification).

Final Answer:

gene bxn in Klebsiella pneumoniae