Q.10 In nature, the horizontal gene transfer across bacteria is mediated by
(A) gene cloning followed by transformation (B)conjugation and transformation
(C) conjugation only (D) transformation only
Horizontal gene transfer (HGT) allows bacteria to rapidly acquire new genetic traits in nature, primarily through conjugation and transformation. The correct answer to the query is (B) conjugation and transformation.
Correct Answer
In nature, horizontal gene transfer across bacteria is mediated by (B) conjugation and transformation. These two natural processes enable bacteria to exchange genetic material without vertical inheritance from parent to offspring. Conjugation involves direct cell-to-cell DNA transfer, while transformation allows uptake of free environmental DNA.
Option Analysis
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(A) Gene cloning followed by transformation: Incorrect, as gene cloning is a laboratory technique using recombinant DNA methods, not a natural process in bacteria.
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(B) Conjugation and transformation: Correct, since both occur naturally; conjugation uses a pilus for plasmid transfer between cells, and transformation involves competent cells absorbing naked DNA from lysed bacteria.
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(C) Conjugation only: Incorrect, as it overlooks transformation, a key natural HGT mechanism alongside conjugation and transduction.
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(D) Transformation only: Incorrect, as conjugation is the most common natural HGT method, especially across species, while transformation is rarer and species-specific.
Key Mechanisms
Horizontal gene transfer drives bacterial evolution, antibiotic resistance, and virulence by enabling quick adaptation.
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Conjugation: Donor bacterium forms a sex pilus to connect with recipient, transferring plasmid DNA (e.g., F-plasmid) via a conjugation bridge; common across Gram-negative and some Gram-positive bacteria.
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Transformation: Recipient bacteria in competent state uptake free DNA from environment (often from dead cells); integrates via recombination, typically within same or related species.
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Note on Transduction: Bacteriophage-mediated, but not in options; completes natural HGT trio.
This knowledge aids biotechnology students in understanding microbial genetics for fermentation, enzyme kinetics, and genetic engineering applications.
