Cels 33

What is the main aim of microbial genetics?

To understand how bacterial DNA is organized and transferred between organisms.

What is the typical structure of the bacterial genome?

A single circular chromosome.

Where is bacterial DNA located?

In the nucleoid region.

Do bacteria have a nuclear membrane?

No, bacteria do not have a nuclear membrane.

What is the nucleoid?

The defined region in the bacterial cell containing the chromosome.

What are plasmids?

Small circular self-replicating DNA molecules separate from the chromosome.

Where are plasmids found?

In the bacterial cytosol.

Why are plasmids important?

They often carry antibiotic resistance and virulence genes.

What is vertical gene transfer?

DNA transfer from parent to offspring.

When does vertical gene transfer occur?

During reproduction/binary fission.

What is horizontal gene transfer (HGT)?

Direct transfer of DNA between organisms.

What is the difference between vertical and horizontal gene transfer?

Vertical transfer is parent-to-offspring, while horizontal transfer is cell-to-cell DNA exchange.

Why is horizontal gene transfer important?

It allows rapid spread of useful traits between bacteria.

What is a de novo mutation?

A new spontaneous mutation.

What are the two major traits commonly transferred horizontally?

Virulence factors and antibiotic resistance genes.

What are virulence factors?

Traits that help bacteria survive in a host and cause disease.

What is an example of a virulence factor in Streptococcus pneumoniae?

The polysaccharide capsule.

Why is the capsule important in Streptococcus pneumoniae?

It increases virulence and protects the bacteria.

What is antibiotic resistance?

The ability of bacteria to survive antibiotic treatment.

What is beta-lactamase?

An enzyme that inactivates penicillin and other beta-lactam antibiotics.

Where are beta-lactamase genes commonly found?

On plasmids.

Why is plasmid-mediated antibiotic resistance dangerous?

A single plasmid can carry multiple resistance genes.

What are the three mechanisms of horizontal gene transfer?

Transformation, transduction, and conjugation.

What is transformation?

Uptake of naked DNA from the environment.

Where does naked DNA in transformation usually come from?

Dead lysed bacteria.

What classic experiment demonstrated transformation?

Griffith’s experiment.

Who performed the classic transformation experiment?

Fred Griffith.

What were the two strains used in Griffith’s experiment?

Smooth (S) and Rough (R) strains of Streptococcus pneumoniae.

Why was the Smooth (S) strain virulent?

It had a polysaccharide capsule.

Why was the Rough (R) strain non-virulent?

It lacked a capsule.

What happened when heat-killed S strain was mixed with live R strain?

The mice died because R cells acquired capsule genes.

What did Griffith’s experiment demonstrate?

Horizontal gene transfer by transformation.

What is transduction?

Virus-mediated transfer of bacterial DNA.

What type of virus carries out transduction?

Bacteriophages.

What are bacteriophages?

Viruses that infect bacteria.

How does transduction occur?

A phage accidentally transfers bacterial DNA to another bacterium.

What is conjugation?

Direct DNA transfer between bacteria through cell contact.

What structure is required for conjugation?

A pilus (sex pilus).

What is the function of the sex pilus?

It connects bacteria and transfers DNA/plasmids.

What type of DNA is commonly transferred during conjugation?

Plasmids.

Why is conjugation clinically important?

It spreads antibiotic resistance rapidly.

Which horizontal transfer mechanisms usually occur within the same species?

Transduction and conjugation.

What is phage therapy?

The use of bacteriophages to treat bacterial infections.

Why is phage therapy useful?

Phages specifically target and kill bacteria.

What is a major advantage of phage therapy?

It can kill antibiotic-resistant bacteria.

Why are bacteriophages considered highly specific?

They target specific bacterial species.

What is an advantage of phage replication during therapy?

Phages replicate at the infection site.

What is a disadvantage of phage therapy?

Bacteria may evolve resistance to phages.

What is another disadvantage of phage therapy?

Possible transfer of toxin genes between bacteria.

What is another limitation of phage therapy?

Limited research and difficult administration.

What is the relationship between bacteriophages and horizontal gene transfer?

Phages can transfer bacterial DNA through transduction.

What is the relationship between plasmids and antibiotic resistance?

Plasmids often carry resistance genes.

What is multidrug resistance?

Resistance to multiple antibiotics.

How can bacteria rapidly evolve?

Through mutation and horizontal gene transfer.

What is the key difference between transformation and conjugation?

Transformation uses naked DNA, while conjugation requires cell contact.

What is the key difference between transformation and transduction?

Transformation uses naked DNA, while transduction uses bacteriophages.

What is the key difference between transduction and conjugation?

Transduction uses viruses, while conjugation uses a pilus.

What bacterial structure mediates cell-to-cell DNA transfer?

The sex pilus.

Why is horizontal gene transfer important in medicine?

It spreads virulence and antibiotic resistance.

What type of DNA molecule is most associated with horizontal transfer?

Plasmids.

What is the major role of bacteriophages in microbial genetics?

Transfer DNA and kill bacteria.