19. The F⁺ segment of bacterta may be transferred to F bacteria by the process of
(1) Conjugation             (2) Transduction
(3) Transformation        (4) Fragmentation

The correct answer is (1) Conjugation, as the F+ plasmid (often called the F+ segment or fertility factor) transfers directly from F+ donor bacteria to F- recipient bacteria through cell-to-cell contact via a sex pilus.​

Option Analysis

• (1) Conjugation: F+ bacteria produce a pilus that forms a bridge with F- cells, allowing single-stranded F plasmid DNA to transfer; the recipient becomes F+ after replication. This process spreads the plasmid rapidly across populations.​

• (2) Transduction: Involves bacteriophages (viruses) packaging and transferring bacterial DNA fragments between cells, unrelated to F+ plasmid or direct contact.​

• (3) Transformation: Bacteria uptake free environmental DNA (e.g., from lysed cells) without donors or pili; F+ plasmid requires conjugation, not naked DNA.​

• (4) Fragmentation: Not a recognized bacterial gene transfer mechanism; lacks biological basis for F+ plasmid movement.​

Bacterial Conjugation Process

F+ cells carry the extrachromosomal F plasmid, enabling pilus formation for mating pair stabilization and DNA transfer initiation. The plasmid nicks, transfers one strand through the pilus conduit, and replicates in both cells, converting F- to F+. This horizontal gene transfer promotes antibiotic resistance spread in bacterial communities.