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

Bacterial HGT Mechanisms: Conjugation + Transformation

Horizontal gene transfer (HGT) drives bacterial evolution by shuttling genetic material between cells, fueling antibiotic resistance and virulence. This MCQ distinguishes natural HGT pathways from lab techniques, crucial for microbiology and biotech curricula.

Correct Answer

(B) conjugation and transformation mediate natural HGT across bacteria. Conjugation transfers plasmids via direct cell-cell contact through sex pili, while transformation involves uptake of naked DNA from lysed cells by competent recipients.

Option Breakdown

(A) Gene Cloning Followed by Transformation

Gene cloning requires artificial restriction digestion, ligation, and electroporation/heat shock—lab manipulation, not natural HGT observed in wild bacterial populations.

(C) Conjugation Only

Conjugation dominates plasmid spread (F-plasmid, R-plasmids), but excludes transformation (e.g., Streptococcus pneumoniae competence) and transduction (phage-mediated), underrepresenting HGT diversity.

(D) Transformation Only

Transformation occurs naturally in competent species (Bacillus, Neisseria), but misses conjugation’s efficiency for large plasmids and interspecies transfer.

Natural HGT Pathways

• Conjugation: Type IV secretion systems pump ssDNA; relaxase resolves hairpin to dsDNA in recipient.

• Transformation: Competence proteins (ComEA/B) bind/import ssDNA; RecA integrates via homologous recombination.

• Transduction: Though unlisted, generalized/specialized phage transfer complements these mechanisms.