Horizontal Gene Transfer and Antibiotic Resistance

These flashcards cover the primary mechanisms of horizontal gene transfer in bacteria, including transformation, transduction, and conjugation, as well as the mobile gene pool and antibiotic resistance.

Horizontal Gene Transfer (HGT)

Any process through which genes are transferred between organisms, also known as lateral gene transfer.

Vertical transfer

The transmission of genes from a parental generation to offspring.

Homologous recombination

An enzyme-catalyzed process where donor DNA integrates into the recipient's chromosome, often using enzymes involved in DNA repair.

Site-specific recombination

An enzymatic process that integrates DNA into a chromosome at a specific sequence.

DNA-mediated transformation

A mechanism of horizontal gene transfer where a cell takes up extracellular or naked DNA from the environment.

Frederick Griffith

The scientist who showed in $1928$ that the ability to synthesize a capsule could be transferred from heat-inactivated smooth strains to living rough strains of Streptococcus pneumoniae.

Avery-MacLeod-McCarty

Researchers who demonstrated in $1944$ that DNA alone, or naked DNA, was sufficient to cause transformation in bacteria.

Competence

The specific ability of a bacterial cell to take up extracellular or naked DNA from its environment.

Transduction

A method of horizontal gene transfer where DNA is transferred from one bacterium to another via a bacteriophage.

Generalized transduction

A process occurring in lytic or temperate phages where an error in packaging results in a transducing particle carrying bacterial DNA instead of phage DNA.

Specialized transduction

A process occurring only in temperate phages where an error in excision during the transition from a lysogenic to a lytic cycle causes flanking bacterial DNA to be taken with the phage DNA.

Lytic phage

A virus that can only replicate and lyse host cells.

Temperate phage

A virus that has the ability to choose between the lytic pathway and the lysogenic pathway.

Transducing particle

A viral protein coat that mistakenly carries bacterial DNA instead of phage DNA, created during an error in the packaging step of generalized transduction.

Defective phage

A phage produced during specialized transduction that lacks some phage genes and instead carries bacterial DNA from the region flanking the integration site.

Conjugation

A DNA transfer mechanism that requires direct cell-to-cell contact and typically involves a conjugative plasmid.

F plasmid

The fertility plasmid which serves as a model for understanding the process of conjugation.

R plasmids

Plasmids that encode resistance to one or more antibiotics; many of these are conjugative.

Core genome

The set of conserved genes that are present in all strains of a particular bacterial species.

Mobile gene pool

Also called the mobilome, this consists of various mobile genetic elements including plasmids, transposons, and genomic islands.

Origin of transfer

The specific site on a plasmid where one DNA strand is cut to initiate the transfer process during conjugation.

Hfr

One of the three types of donor cells involved in conjugation, alongside $F+$ and $F'$.

DNase sensitivity

A characteristic of DNA-mediated transformation, which can be inhibited or stopped by the addition of the enzyme DNase.

GC content

A genomic signature used to identify horizontally acquired genes because they often exhibit a different ratio of guanine and cytosine than the rest of the genome.

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