Bacterial Metabolism and Genetics: Gene Exchange
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What primary mechanism contributes to Vancomycin-Intermediate S. aureus (VISA) strains exhibiting reduced susceptibility to vancomycin?

  • Increased expression of efflux pumps that actively remove vancomycin from the bacterial cell.
  • Genetic mutations that alter the structure of the vancomycin molecule itself.
  • Decreased production of peptidoglycan precursors, reducing the binding sites for vancomycin.
  • Thickening of the cell wall, which hinders vancomycin's ability to reach its target. (correct)

What is the primary consequence of phages oversaturating a host cell?

  • The phage DNA integrates into the bacterial chromosome, forming a prophage.
  • The bacterial cell begins producing viral proteins for its own benefit.
  • A lytic event occurs, releasing phages and killing the host cell. (correct)
  • The host cell gains resistance to further phage infections.

The first clinical isolate of S. aureus with decreased susceptibility to vancomycin was reported in what country?

  • United Kingdom
  • Japan (correct)
  • United States
  • Germany

Under what circumstance might a phage within a bacterial cell undergo a lytic cycle?

<p>Upon exposure to certain inducing conditions. (A)</p> Signup and view all the answers

What is the minimum inhibitory concentration (MIC) value that defines Vancomycin-Intermediate S. aureus (VISA)?

<p>MIC ≤ 16 µg/mL (D)</p> Signup and view all the answers

What is a key characteristic of transposons?

<p>They are mobile genetic elements capable of moving within or between DNA molecules. (A)</p> Signup and view all the answers

In the case study mentioned, what underlying conditions did the patient with the high-level vancomycin-resistant S. aureus (VRSA) infection have?

<p>Hypertension, diabetes mellitus, peripheral vascular disease, and chronic renal failure (A)</p> Signup and view all the answers

What type of infection did the patient with high-level vancomycin-resistant S. aureus (VRSA) present with?

<p>Diabetic foot ulcer with gangrenous digit (D)</p> Signup and view all the answers

A researcher identifies a new insertion sequence in a bacterial genome. What two components would confirm its identity as an insertion sequence?

<p>Inverted repeats and a transposase gene. (B)</p> Signup and view all the answers

A plasmid in a bacterial cell contains a transposon. If this transposon moves from the plasmid to the bacterial chromosome, what is the most likely consequence?

<p>A change in the bacterial chromosome's genetic makeup. (C)</p> Signup and view all the answers

What is the MIC of the high level vancomycin resistant S. aureus?

<p>1024 µg/mL (A)</p> Signup and view all the answers

Methicillin-resistant Staphylococcus aureus (MRSA) exhibits resistance to which class of antibiotics?

<p>β-lactams (D)</p> Signup and view all the answers

The high level vancomycin resistant S. aureus sample in the case study was taken from a patient in what US state?

<p>Michigan (A)</p> Signup and view all the answers

According to the image, what is the implication of prolonged vancomycin use?

<p>It leads to the promotion of Vancomycin-Resistant <em>Staphylococcus aureus</em> (VRSA). (A)</p> Signup and view all the answers

Based on the image, which genetic transfer mechanisms are potentially involved in the spread of MrsA?

<p>Transformation or Conjugation (C)</p> Signup and view all the answers

What is the likely meaning of 'VRSA' in the context of the image?

<p>Vancomycin-Resistant <em>Staphylococcus aureus</em> (D)</p> Signup and view all the answers

If a patient has an infection with MrsA, what genetic mechanisms could have contributed to the bacteria acquiring a new resistance plasmid?

<p>Transformation or Conjugation (C)</p> Signup and view all the answers

How might the use of vancomycin influence the prevalence of VRSA in a hospital environment?

<p>Increased vancomycin use may promote the selection and spread of VRSA. (D)</p> Signup and view all the answers

What is the relationship between MrsA and the development of vancomycin resistance?

<p>MrsA picked up a plasmid either through transformation or conjugation. (B)</p> Signup and view all the answers

Which patient factor, included in the image, might increase the risk of VRSA infection?

<p>Diabetes. (A)</p> Signup and view all the answers

What is the primary significance of genetic transfer mechanisms like transformation and conjugation in the context of antibiotic resistance?

<p>They facilitate the horizontal transfer of resistance genes between bacteria. (C)</p> Signup and view all the answers

According to the information provided, what genetic mechanism is associated with the transfer of resistance genes?

<p>Conjugation facilitated by mutated progeny. (B)</p> Signup and view all the answers

In the experiment described, what genetic element facilitated the presence of resistance genes?

<p>A transposable element. (A)</p> Signup and view all the answers

What is the likely role of the probe used in the experiment by Weigel et al. (2003)?

<p>To identify the presence of a specific gene in VRSA. (D)</p> Signup and view all the answers

What can be deduced about the relationship between lanes 3 and 4?

<p>They have identical genetic content except for the presence of a specific gene in lane 4. (A)</p> Signup and view all the answers

Based on the information, what is the significance of the D-Ala (D-Alanine) mentioned?

<p>It is a modified form of alanine that confers resistance to vancomycin. (C)</p> Signup and view all the answers

What is the primary role of plasmids in bacterial cells?

<p>To offer a selective advantage, such as antibiotic resistance or virulence factors. (C)</p> Signup and view all the answers

A bacterium gains resistance to an antibiotic. Which mechanism would MOST likely lead to rapid spread of this resistance to other bacteria?

<p>Gene exchange via plasmids. (C)</p> Signup and view all the answers

How do episomes differ from other types of plasmids?

<p>Episomes can integrate into the host chromosome, while other plasmids cannot. (B)</p> Signup and view all the answers

What distinguishes the lytic cycle from the lysogenic cycle in bacteriophages?

<p>The lytic cycle results in host cell lysis, whereas the lysogenic cycle allows the host to survive. (D)</p> Signup and view all the answers

A researcher introduces a bacteriophage into a bacterial culture. After several generations, most of the bacteria die, but some survive and incorporate the phage DNA into their genome. What process has occurred?

<p>Lytic cycle followed by lysogenic conversion. (C)</p> Signup and view all the answers

Which of the following mechanisms of gene exchange in prokaryotes requires direct physical contact between two cells?

<p>Conjugation. (A)</p> Signup and view all the answers

How does the exchange of DNA contribute to the evolution and adaptation of bacteria?

<p>It generates new strains with altered characteristics, such as antibiotic resistance, which can be advantageous. (B)</p> Signup and view all the answers

If a bacterium contains a plasmid with a gene for a novel enzyme that degrades a toxic pollutant, under which conditions would this plasmid be MOST beneficial to the bacterium?

<p>In an environment heavily contaminated with the pollutant. (B)</p> Signup and view all the answers

Consider a bacterial population where some cells have become resistant to a particular antibiotic due to a gene located on a plasmid. What is the MOST likely outcome if the antibiotic is removed from their environment?

<p>The resistant cells will likely lose the plasmid over time if it is not needed, due to the metabolic burden. (C)</p> Signup and view all the answers

A researcher discovers a new bacteriophage that exclusively infects bacteria containing a specific plasmid. How could this bacteriophage be utilized in a biotechnology application?

<p>To selectively eliminate bacteria containing the specific plasmid in a mixed culture. (A)</p> Signup and view all the answers

A bacterial cell's mating type is determined by the presence or absence of what?

<p>A conjugative plasmid (F plasmid) (A)</p> Signup and view all the answers

What is the primary function of the sex pilus in bacterial conjugation?

<p>To attach to another bacterium and initiate DNA transfer (A)</p> Signup and view all the answers

In specialized transduction, a phage transfers which type of genes?

<p>Genes located near the prophage integration site (A)</p> Signup and view all the answers

What occurs during generalized transduction?

<p>Random fragments of host DNA are packaged into phage particles (B)</p> Signup and view all the answers

The diphtheria toxin produced by Corynebacterium diphtheriae is encoded by a gene carried by what?

<p>Corynephage beta (D)</p> Signup and view all the answers

What clinical manifestation is described by the term "Bull neck" in the context of a Corynebacterium diphtheriae infection?

<p>Massive swelling in the neck region (D)</p> Signup and view all the answers

A bacterium has acquired a new gene that provides resistance to a specific antibiotic. Which mechanism of genetic transfer is least likely to be responsible for this acquisition?

<p>Spontaneous mutation in the bacterial chromosome (C)</p> Signup and view all the answers

A researcher identifies a new bacterial strain that produces a novel toxin. Further analysis reveals that the gene encoding the toxin is located within a prophage integrated into the bacterial chromosome. Which of the following statements is most likely true?

<p>The toxin gene can be transferred to other bacteria via transduction. (A)</p> Signup and view all the answers

A bacterium gains the ability to produce a sex pilus. What is the most direct consequence of this acquisition?

<p>The ability to initiate conjugation (D)</p> Signup and view all the answers

Following an outbreak of diphtheria, public health officials are trying to determine the source. They culture Corynebacterium diphtheriae from multiple patients and analyze the bacterial strains. What genetic characteristic would be most important to examine to assess the virulence and potential for transmission?

<p>The presence of the corynephage beta (D)</p> Signup and view all the answers

Flashcards

Phage oversaturation

When phages replicate excessively in a host cell, leading to cell death.

Lytic cycle

The process where a virus replicates within a host cell and eventually causes the cell to burst.

Gene exchange in prokaryotes

The process by which genetic material is transferred between prokaryotic cells, enhancing genetic diversity.

Transposons

Mobile genetic elements that can move within a genome or between DNA molecules.

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Insertion Sequence

The simplest form of transposon, consisting only of inverted repeats and transposase.

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Gene Exchange

The process by which prokaryotic cells transfer DNA to one another.

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Promiscuous Bacteria

Bacteria that readily exchange genetic material with others.

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New Strains

Genetically different versions of bacteria resulting from gene exchange.

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Plasmids

Small, circular, extrachromosomal DNA that replicates independently.

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Episomes

Plasmids that can integrate into the host chromosome.

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Bacteriophages

Viruses that infect bacterial cells and can contain DNA or RNA.

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Lysogenic Cycle

The process where a virus integrates its genome into the host without killing it.

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Antibiotic Resistance

The ability of bacteria to survive despite antibiotic treatment.

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Virulence Factors

Traits that enhance a bacterium's ability to cause disease.

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Vancomycin Resistance

A type of antibiotic resistance that occurs in bacteria like S. aureus.

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Transposable Elements

DNA sequences that can change position within a genome, potentially altering gene function.

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Conjugation

A method of genetic transfer in bacteria where genetic material is exchanged through direct contact.

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VRE Plasmids

Plasmids containing genes that confer vancomycin resistance to bacteria.

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MRSA and VRSA

Types of Staphylococcus aureus: MRSA is resistant to methicillin; VRSA is resistant to vancomycin.

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MRSA

Methicillin-resistant Staphylococcus aureus, a type of bacteria resistant to common antibiotics.

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Vancomycin

An antibiotic used to treat serious bacterial infections, effective against Gram-positive bacteria.

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VISA

Vancomycin Intermediate Susceptible Staphylococcus aureus, showing decreased susceptibility to vancomycin.

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MIC

Minimum Inhibitory Concentration, the lowest concentration of an antibiotic that prevents bacterial growth.

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Gangrenous digit

A body part, usually a toe or finger, that has died due to lack of blood flow or infection.

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Diabetes mellitus

A chronic condition characterized by high blood sugar levels due to insufficient insulin.

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Peripheral vascular disease

A circulatory condition that narrows blood vessels, decreasing blood flow to limbs.

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Chronic renal failure

A long-term condition where the kidneys gradually lose function.

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Vancomycin-Resistant Enterococcus (VRE)

A type of bacteria that has developed resistance to the antibiotic vancomycin.

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Vancomycin-Resistant Staphylococcus aureus (VRSA)

A strain of Staphylococcus aureus that is resistant to vancomycin.

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Plasmid Transfer

The process by which genetic material is transferred from one bacterium to another via plasmids.

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Transformation

The uptake of foreign DNA by a bacteria from its surroundings.

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Genetic Manipulation

Techniques used to alter the genetic makeup of an organism.

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Molecular Resistance Mechanisms

The various ways bacteria become resistant to antibiotics at the molecular level.

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Antibiotic Resistance Promotion

Factors that encourage bacteria to develop resistance to antibiotics.

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F Plasmid

A plasmid carrying genes for its own transfer and the ability to make sex pilus.

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Transduction

A genetic transfer mechanism mediated by bacteriophages, transferring DNA between bacteria.

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Generalized Transduction

Random incorporation of host DNA into phage capsid, possibly transferring any bacterial gene.

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Specialized Transduction

Transfer of specific genes located near a phage's integration site into a host bacterium.

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Corynephage Beta

A lysogenic phage that carries the gene for the diphtheria toxin.

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Diphtheria Toxin

A toxin produced by Corynebacterium diphtheriae that causes respiratory issues.

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Prophage

A phage that is integrated into the bacterial genome and can remain dormant.

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Sex Pilus

A structure made by bacteria to connect during conjugation and transfer DNA.

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Vancomycin-Resistant Bacteria

Bacteria that have developed resistance to the antibiotic vancomycin, often requiring alternative treatments.

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Study Notes

Bacterial Metabolism and Genetics: Gene Exchange in Prokaryotic Cells

  • Pathogenic bacteria often exchange DNA, a trait called "promiscuous" DNA exchange.
  • This DNA exchange allows for the exchange of genes and characteristics between cells, generating new strains.
  • Gene exchange can be advantageous for the recipient, such as through antibiotic resistance.
  • Exchanged genes can be integrated into the recipient's chromosome or remain as an extrachromosomal element (like a plasmid) or bacteriophage. They're then passed to daughter cells.
  • Plasmids are small, circular DNA molecules replicating independently of the chromosome. They often carry genes for antibiotic resistance, toxins, and virulence factors. Replicate autonomously or can integrate into the host's chromosome (episomes).

Bacterial Gene Exchange: Plasmids

  • Plasmids are small genetic elements replicating independently of the chromosome.
  • Usually circular and double-stranded, ranging from 1500 to 400,000 base pairs.
  • Genetic information commonly isn't critical but can provide selective advantages, often carrying antibiotic resistance, bacteriocins, toxins, and virulence factors.
  • Plasmids replicate autonomously, acting as replicons.
  • Some plasmids can integrate into the host chromosome, becoming episomes.

Bacterial Gene Exchange: Bacteriophages

  • Bacteriophages (phages) are bacterial viruses, carrying DNA or RNA genomes shielded by protein coats.
  • They infect bacterial cells through a lytic or lysogenic cycle.
  • Lytic: phages replicate and cause the cell to burst (lyse).
  • Lysogenic: phages integrate into the host genome and are replicated without killing the cell (prophage).

Bacterial Gene Exchange: Transposons

  • Transposons, or "jumping genes," are mobile genetic elements.
  • They transfer DNA within a cell, or between different DNA molecules (e.g., plasmid to plasmid or plasmid to chromosome).
  • The simplest transposons are insertion sequences, which have inverted repeats and transposase genes. Complex transposons also contain genes for transposition and other genes (antibiotic resistance, toxins).

Mechanisms of Genetic Transfer Between Cells

  • Conjugation: One-way DNA transfer from a donor (male) cell to a recipient (female) cell through a conjugation pilus. Usually between similar or related species. Mating type depends on the presence (male) or absence (female) of a conjugative plasmid. Plasmids often carry genes essential to their own transfer.
  • Transduction: DNA transfer mediated by bacteriophages (bacterial viruses). Specialized transduction involves transfer of specific phage genes, often adjacent to their integration site in the host genome. Generalized transduction involves random incorporation of host DNA fragments into the phage capsid.
  • Transformation: Process where bacteria take up naked DNA, incorporating it into their genome. Gram-positive and Gram-negative bacteria can perform this process, with some species exhibiting natural competence.

Pathogenicity and Virulence Islands

  • Pathogenicity and virulence often involve coordinated gene expression within pathogenicity islands, segments of a bacteria's genome.
  • These islands can relocate within the chromosome and to other bacteria. Their expression is often triggered by environmental stimulation.

Generation of Vancomycin-Resistant S. aureus

  • MRSA (Methicillin-resistant Staphylococcus aureus) and VISA (Vancomycin-intermediate S. aureus) were clinically characterized. A high level of vancomycin-resistant S. aureus (VRSA) emerged from a dialysis patient in Michigan in 2002, demonstrating possible multiple genetic manipulations.

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Description

Pathogenic bacteria frequently exchange DNA, a trait called 'promiscuous' DNA exchange. This exchange allows for the transfer of genes and characteristics, leading to new strains. Plasmids are small, circular DNA molecules that replicate independently and commonly carry genes for antibiotic resistance.

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