Bacterial Genetics

What is horizontal gene transfer and its significance?

The process by which bacteria exchange genetic material allows rapid spread of antibiotic resistance and can convert harmless microbes into pathogenic ones.

What is bacterial transformation?

The uptake of 'naked' DNA from the environment by bacteria.

What regulates competence in bacterial transformation?

Competence is regulated by a quorum sensing mechanism.

What is the first step in the transformation process?

Double stranded DNA binds to surface proteins of the bacterial cell.

What happens to the DNA during the transformation process?

One strand is cleaved while the other strand is coated and brought into the cell.

What mechanism incorporates single-stranded DNA into the bacterial genome?

Homologous recombination.

What is homologous recombination?

The process where incoming DNA must have a long stretch of similar sequence to the host DNA for incorporation.

What role does RecA protein play in homologous recombination?

RecA coats the incoming strand and helps form a temporary triplex with the chromosomal DNA.

What is natural transformation?

A process allowing variation in surface antigens of microbes to evade the immune system.

What are plasmids?

Small circular DNA molecules that provide beneficial genes, such as antibiotic resistance, but are not essential for bacterial survival.

What is bacterial conjugation?

The direct exchange of plasmid DNA between bacterial cells requiring cell-to-cell contact.

What is an Hfr strain?

A bacterium with a plasmid integrated into its chromosome which allows for the transfer of chromosomal DNA during conjugation.

What happens during generalized transduction?

Viruses mistakenly package degraded chromosomal DNA into their capsids, which is then transferred to new hosts.

What is specialized transduction?

When a lysogenic phage incorrectly excises some chromosomal DNA from its host and transfers it to another bacterium.

What distinguishes prototrophic bacteria from auxotrophic bacteria?

Prototrophic bacteria can grow in minimal media while auxotrophic bacteria lack genes required for synthesizing certain nutrients.

What does DNAse treatment in a mixture indicate?

The addition of DNAse rules out the possibility of transformation if no colonies occur.

How can blocking cell-to-cell contact affect conjugation?

It prevents conjugation from occurring and allows for the study of other gene transfer mechanisms.

What criteria define a biological species according to bacteriologists?

A high degree of relatedness in housekeeping genes and a common ecological niche or habitat.

How can differences in Heliobacter pylori genomes affect species designation?

Despite genome differences, they can share identical ecotypes, complicating classification.

What is the significance of the F prime plasmid?

It carries extra chromosomal DNA that can be transferred during conjugation.

How does phage therapy interact with antibiotic resistance?

Phage therapy can be used to target multi-drug resistant plasmids, reducing antibiotic resistance.

What is the role of CRISPR in combating antibiotic resistance?

CRISPR targets and destroys antibiotic-resistant genes within bacterial plasmids.

What could happen to bacterial cells resistant to CRISPR/Cas phage?

They can be either killed by a second phage or lose their resistance plasmid, becoming susceptible to antibiotics.

What kind of genetic exchange occurs when plasmids are transferred?

The exchange of beneficial traits, such as antibiotic resistance, between bacterial strains.

Describe the significance of the quorum sensing mechanism.

It ensures that bacteria are likely to encounter DNA, thereby promoting transformation.

What is a heteroduplex in the context of transformation?

It is formed when the incoming strand differs from the original, and is resolved by replication or repair.

Why is it said that only parts of the chromosome are typically transferred in conjugation?

This is due to the nature of F plasmids inserting into chromosomes and initiating transfer from specific points.

What does the average nucleotide identity of orthologs being > 95% indicate?

A high genetic similarity between bacterial species, defining taxonomic relationships.