Bacterial Conjugation and Plasmids
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Questions and Answers

What is the primary function of the F plasmid in bacterial conjugation?

  • To facilitate DNA transfer from a donor to a recipient cell. (correct)
  • To encode pathogenic traits in bacteria.
  • To replicate bacterial chromosomal DNA.
  • To encode antibiotic resistance genes.

What is the consequence of the successful transfer of the F plasmid to an F- cell?

  • The recipient cell dies due to the plasmid transfer.
  • The recipient cell becomes resistant to antibiotics.
  • The recipient cell becomes an R+ cell.
  • The recipient cell becomes an F+ cell. (correct)

Which of the following best describes the process by which the F plasmid is replicated during conjugation?

  • Rolling-circle replication at the binding point. (correct)
  • Conservative replication where the original DNA is preserved.
  • Replication by homologous recombination with the host chromosome.
  • Bidirectional replication from a single origin.

Besides the F plasmid, what other kind of plasmid is mentioned in the text?

<p>R (resistance) plasmids (A)</p> Signup and view all the answers

What is the role of transposable elements in the context of R (resistance) plasmids?

<p>They contribute to the acquisition of antibiotic resistance genes. (C)</p> Signup and view all the answers

Which process is exclusively performed by archaea?

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

What is the primary structural component of bacterial cell walls?

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

How does genetic recombination primarily occur in prokaryotes?

<p>Horizontal gene transfer (C)</p> Signup and view all the answers

What type of linkages joins fatty acid chains to glycerol in bacterial membrane lipids?

<p>Ester linkages (C)</p> Signup and view all the answers

Which of the following describes the flagella of archaea, compared to bacteria?

<p>They evolved independently (C)</p> Signup and view all the answers

Which characteristic is NOT typical of prokaryotic cells?

<p>Membrane-bound organelles (B)</p> Signup and view all the answers

What is the difference between glycerol stereoisomers in bacteria versus archaea?

<p>Bacteria use glycerol-3-phosphate, archaea use glycerol-1-phosphate (C)</p> Signup and view all the answers

What is a common function of plasmids found in prokaryotes?

<p>Carry extra genes (A)</p> Signup and view all the answers

How does the process of DNA replication in archaea compare to that in eukaryotes?

<p>Both use the same single replication origin (B)</p> Signup and view all the answers

Which of the following shapes is NOT a typical bacterial cell shape?

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

What is the primary function of plasmids found within bacteria?

<p>To provide a selective advantage under certain conditions. (A)</p> Signup and view all the answers

Why are bacterial ribosomes a target for some antibiotics?

<p>Because their unique protein and RNA content allows for selective inhibition. (D)</p> Signup and view all the answers

Which of the following characteristics was NOT traditionally used for early classification of bacteria?

<p>The sequencing of their whole genome. (C)</p> Signup and view all the answers

What is a key principle behind the nucleic acid hybridization technique used for bacterial classification?

<p>Closely related species will have more base pairing between their single-stranded DNA. (C)</p> Signup and view all the answers

Which of the following best describes the current understanding of bacterial diversity?

<p>The majority of bacteria have never been cultured or studied in detail. (D)</p> Signup and view all the answers

What is a common mechanism of horizontal gene transfer in bacteria and archaea?

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

How does transduction contribute to genetic diversity in prokaryotes?

<p>By using viruses to transfer DNA between cells. (B)</p> Signup and view all the answers

What is a characteristic of plasmids that distinguishes them from the primary bacterial chromosome?

<p>They are not required for normal function but may provide an advantage. (B)</p> Signup and view all the answers

Which process involves the transfer of bacterial DNA via a virus?

<p>Transduction (B)</p> Signup and view all the answers

What mechanism facilitates the incorporation of new DNA into a recipient cell's genome during transformation?

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

How does artificial transformation differ from natural transformation?

<p>Artificial transformation can be induced in the lab, while natural transformation occurs spontaneously. (B)</p> Signup and view all the answers

What specific components are required for the integration of an F plasmid into a bacterial chromosome?

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

In general transduction, which of the following is packed into a new phage head?

<p>Either viral or bacterial DNA (B)</p> Signup and view all the answers

Which of the following statements is true regarding horizontal gene transfer?

<p>It can occur through conjugation, transduction and transformation. (A)</p> Signup and view all the answers

What is the primary source of DNA fragments in natural transformation?

<p>Damaged or dead cells (B)</p> Signup and view all the answers

Which process is NOT a method of horizontal gene transfer?

<p>Meiosis (B)</p> Signup and view all the answers

What is the primary function of peptidoglycan in bacterial cell walls?

<p>To provide a rigid network and maintain cell shape. (D)</p> Signup and view all the answers

Which of the following is a key difference between Gram-positive and Gram-negative bacteria?

<p>Gram-positive bacteria have a thicker peptidoglycan layer and contain lipoteichoic and teichoic acid. (C)</p> Signup and view all the answers

What is the role of the capsule found in some bacteria?

<p>To protect the cell from the immune system and aid in attachment. (D)</p> Signup and view all the answers

Which structure is primarily involved in bacterial locomotion?

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

What is the function of pili in gram-negative bacteria?

<p>To aid in attachment and conjugation. (D)</p> Signup and view all the answers

Under what condition do endospores primarily form?

<p>When the bacteria are exposed to environmental stress. (C)</p> Signup and view all the answers

What is a characteristic of endospores regarding environmental conditions?

<p>They are resistant to environmental stress, like heat. (C)</p> Signup and view all the answers

What are the invaginated regions of the plasma membrane in prokaryotic cells primarily involved in?

<p>Respiration or photosynthesis. (A)</p> Signup and view all the answers

Which of these bacteria-caused diseases is associated with endospore formation?

<p>Tetanus, botulism, and anthrax. (B)</p> Signup and view all the answers

What is contained within the endospores?

<p>The genome and a small portion of the cytoplasm. (C)</p> Signup and view all the answers

Which of the following bacterial diseases is primarily transmitted through improperly prepared food?

<p>Botulism (B)</p> Signup and view all the answers

What is the primary cause of dental caries?

<p>Acid production by bacteria like <em>Streptococcus mutans</em> (D)</p> Signup and view all the answers

Which disease is characterized by a lesion followed by symptoms like malaise, fever, and stiff neck, and is transmitted by a tick bite?

<p>Lyme disease (C)</p> Signup and view all the answers

Which of these diseases is spread primarily through respiratory droplets?

<p>Diphtheria (B)</p> Signup and view all the answers

Which bacterial disease is known for causing severe diarrhea and is associated with poor sanitation?

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

Which of the following diseases is NOT typically transmitted through insect vectors?

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

Which bacterial disease is characterized by chronic skin infection and is associated with armadillos as a reservoir?

<p>Hansen disease (leprosy) (D)</p> Signup and view all the answers

Which of the following diseases has seen an increase in incidence recently with some antibiotic-resistant strains?

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

Which of these diseases can be contracted through contaminated water or food?

<p>Typhoid fever (C)</p> Signup and view all the answers

Which of these diseases is primarily transmitted sexually?

<p>Chlamydia (C)</p> Signup and view all the answers

Which bacteria is associated with causing peptic ulcers?

<p><em>Helicobacter pylori</em> (A)</p> Signup and view all the answers

What is the main way that Rickettsia typhi, the cause of typhus, is transmitted?

<p>Through the bite of lice and fleas (D)</p> Signup and view all the answers

Which disease is associated with the bacterium Bacillus anthracis?

<p>Anthrax (B)</p> Signup and view all the answers

Which bacterial disease is caused by Neisseria gonorrhoeae?

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

Which of the following is NOT a common causative agent of pneumonia?

<p><em>Borrelia</em> (C)</p> Signup and view all the answers

Flashcards

Prokaryotic Cell Structure - Unicellularity

Single-celled organisms that may form associations or biofilms. They lack extensive membrane-bound organelles and are generally less than 1 µm in diameter.

Prokaryotic Cell Structure - Cell Division

Most prokaryotes divide asexually via binary fission, a process where one cell splits into two.

Prokaryotic Cell Structure - Chromosomes

Prokaryotes have a single circular chromosome and often contain plasmids, which are small, circular DNA molecules separate from the chromosome. They are involved in horizontal gene transfer.

Prokaryotic Cell Structure - Flagella

Prokaryotic flagella are single protein fibers that rotate like propellers to allow movement. They are distinct from eukaryotic flagella.

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Prokaryotic Cell Structure - Metabolic Diversity

Prokaryotes exhibit a wide range of metabolic processes, encompassing both oxygenic and anoxygenic photosynthesis, as well as chemolitotrophic metabolism.

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Prokaryotic Cell Structure - Bacteria Membrane Lipids

In bacteria, fatty acid chains are linked to glycerol phosphate with ester linkages. The membranes are typically unbranched and diethers.

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Prokaryotic Cell Structure - Archaea Membrane Lipids

In archaea, non-polar hydrocarbons called isoprenoids are linked to glycerol phosphate with ether linkages. The membranes can be branched, cyclic, and may be tetraethers forming monolayers.

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Bacteria versus Archaea - Cell Wall

Bacteria possess peptidoglycan in their cell walls, while archaea lack it. Archaea may have an S-layer outside or replacing the cell wall, composed of glycoproteins forming a rigid, crystalline surface.

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Bacteria versus Archaea - Unique Flagella

Archaea have unique flagella that evolved independently of bacterial flagella.

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Bacteria versus Archaea - DNA Replication

Both bacteria and archaea have a single replication origin for their DNA, however, archaeal initiation proteins are more similar to those found in eukaryotes.

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Bacterial Cell Wall

A rigid structure that surrounds the bacterial cell, made up of peptidoglycan which is a unique molecule to bacteria. It maintains the cell shape and helps bacteria withstand changes in osmotic pressure.

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Gram-positive bacteria

A thick layer of peptidoglycan found in bacteria that stains purple with a Gram stain. They are usually more susceptible to antibiotics.

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Gram-negative bacteria

A thin layer of peptidoglycan found in bacteria that do not retain the purple stain in a Gram stain. They have an outer membrane and are often resistant to many antibiotics.

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Gram stain

A special stain used to classify bacteria based on their cell wall structure. It distinguishes bacteria into Gram-positive and Gram-negative.

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Capsule

A gelatinous layer that surrounds some bacteria, aiding in attachment to surfaces and providing protection from the immune system.

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Flagella

Long, whip-like structures made of flagellin protein that help bacteria move around by spinning like a propeller.

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Pili

Short, hair-like structures found in gram-negative bacteria. They help with attachment to surfaces and with conjugation, a process of transferring genetic material.

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Endospore

A dormant, highly resistant form of bacteria that forms when exposed to unfavorable conditions like heat or lack of nutrients. It has a thick wall around its genome and a small portion of cytoplasm. Once conditions improve, it can germinate and return to normal.

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Internal Membranes in Bacterial Cells

Internal membranes found in prokaryotic cells. These invaginations of the plasma membrane function in respiration or photosynthesis.

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Conjugation

The process of a bacterium transferring genetic material to another bacterium through direct contact, often aided by pili.

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Nucleoid region

A region within a bacterial cell that contains the single, circular chromosome, often including plasmids.

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Plasmids

Small, independently replicating DNA molecules found in bacteria, often carrying genes that provide selective advantages like antibiotic resistance.

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Ribosomes in bacterial cells

The site of protein synthesis in bacterial cells, smaller than those found in eukaryotes and with different protein and RNA content.

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Early Classification Characteristics

Methods of bacterial classification based on observable traits like motility, shape, and ability to form spores.

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Molecular Classification

A method of bacterial classification based on comparing the amino acid sequences of key proteins, hybridization of nucleic acids, and sequencing of genes and RNA.

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Transduction

The transfer of bacterial DNA through viruses (bacteriophages) as a carrier.

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Transformation

The uptake of naked DNA from the environment by bacterial cells.

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Bacterial Conjugation

The process of transferring genetic material from one bacterial cell to another through direct contact.

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F+ Cell

A bacterial cell containing the F plasmid, capable of transferring genetic material during conjugation.

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F- Cell

A bacterial cell lacking the F plasmid, unable to initiate conjugation.

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R Plasmid

A type of plasmid that carries genes for resistance to antibiotics, providing an advantage for bacteria in antibiotic-rich environments.

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Horizontal Gene Transfer

Genetic exchange between organisms that are not related through descent; a major mechanism of evolution in bacteria.

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Generalized Transduction

A type of transduction that occurs when a phage inadvertently packages bacterial DNA into a phage head rather than its own genome.

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Natural Transformation

When a bacterial cell picks up DNA fragments released from dead cells, the DNA integrates into the cell's genome through homologous recombination.

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Artificial Transformation

A process in which a bacterial cell is induced to take up foreign DNA in a laboratory setting, crucial for genetic engineering and DNA manipulation.

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Anthrax

A bacterial infection that can be transmitted through contact or ingestion. It is rare except in sporadic outbreaks and can be fatal.

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Botulism

A bacterial infection contracted through ingestion or contact with a wound. It produces acute toxic poison and can lead to death.

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Chlamydia

A bacterial infection that can be transmitted through sexual contact. It can spread to the eyes and respiratory tract. It is becoming more common.

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Cholera

A bacterial infection that is spread through contaminated water or food. It causes severe diarrhea and can lead to dehydration and death. It is a major killer in crowded areas with poor sanitation.

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Diphtheria

A bacterial infection that is spread through respiratory droplets. It causes inflammation and lesions of the respiratory membranes. There is a vaccine available.

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Gonorrhea

A bacterial infection that is spread through sexual contact. It is on the increase worldwide, and left untreated it can be fatal.

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Hansen’s Disease (Leprosy)

A bacterial infection that affects the skin. It is a chronic infection and there are about 10–12 million infected individuals worldwide. It is spread through contact with infected individuals.

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Lyme Disease

A bacterial infection spread through the bite of an infected tick. It causes a lesion followed by fever, fatigue, pain, stiff neck, and headache.

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Peptic Ulcers

A bacterial infection that was once thought to be caused by stress or diet. It is now known to be caused by a bacterium.

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Plague

A bacterial infection that was a major killer in the 14th century. It is endemic in wild rodent populations in the western US today.

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Pneumonia

A bacterial infection that causes an acute infection of the lungs. It can be fatal without treatment, but there is a vaccine available.

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Tuberculosis (TB)

A bacterial infection that can affect the lungs, lymph nodes, and meninges. Its incidence is on the rise, including antibiotic-resistant strains.

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Typhoid Fever

A bacterial infection that affects the body systemically. It is spread through contaminated water and food. There are vaccines available.

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Typhus

A bacterial infection that was a major killer in times of crowding and poor sanitation. It is transmitted through the bite of infected lice and fleas.

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Study Notes

Prokaryotes

  • Small, simple, and abundant life forms, originating over 3.5 billion years ago
  • Characterized by their lack of membrane-bound organelles
  • Two domains: Bacteria and Archaea
  • Bacteria produced oxygen, leading to greater biological diversity
  • Archaea are extremophiles, the earliest discovered prokaryotes
  • Prokaryotes are one of the three domains of life
  • Two domains are not closely related

Prokaryote Characteristics

  • Unicellularity: Single-celled organisms that can form associations like biofilms.
  • Cell size: Most are less than 1 µm in diameter.
  • Cell Division: Primarily through binary fission (asexual reproduction).
  • Chromosomes: Single, circular chromosome. May have smaller, circular plasmids.
  • Genetic Recombination: Occurs via horizontal gene transfer, not sexual reproduction.
  • Flagella: Single protein fibers that rotate like propellers for locomotion.
  • Metabolic diversity: Include oxygenic and anoxygenic photosynthesis, and chemolithotrophy (energy from oxidizing inorganic substances).

Prokaryote Membrane Lipids

  • Bacteria: Fatty acid chains joined to glycerol phosphate via ester linkages. Membranes are unbranched and are diethers.
  • Archaea: Non-polar hydrocarbons (isoprenoids) attached to glycerol phosphate via ether linkages. Membranes can be branched and include cyclic compounds, and tetraethers that can form a monolayer membrane.

Bacteria versus Archaea

  • Cell wall: Bacteria have peptidoglycan; archaea lack it, instead having S-layers on the outside of their walls or replacing their walls.
  • Unique flagella: Evolved independently from bacterial flagella.
  • DNA replication: Both have a single replication origin, but archaeal initiation proteins are more similar to eukaryotes.
  • Gene expression: Both have transcription-translation coupling; machinery in archaea is more similar to eukaryotes.
  • Methanogenesis: All organically produced methane comes from archaea.
  • Ammonia oxidation: Aerobic ammonia oxidation is found only in archaea.

Prokaryotic Cell Structure

  • Shapes: Bacteria have three basic shapes: bacillus (rod-shaped), coccus (spherical), and spirillum (helical-shaped).
  • Cell Walls: Peptidoglycan forms a rigid network unique to bacteria, maintaining shape and withstanding hypotonic environments. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. Gram-negative bacteria have a thinner peptidoglycan layer and do not retain purple stain, appearing dark pink.

Capsule

  • Gelatinous layer found in some bacteria, surrounding the cell wall. It aids attachment and protects from the immune system.

Bacterial Flagella and Pili

  • Flagella: Slender, rigid, helical structures composed of flagellin, involved in locomotion.
  • Pili: Short, hairlike structures found in gram-negative bacteria, aiding in attachment and conjugation.

Endospores

  • Develop a thick wall around their genome and a small portion of the cytoplasm, forming when exposed to environmental stress. Endospores are highly resistant to environmental stress, particularly heat.
  • When conditions improve, endospores can germinate and return to normal cell division. Bacteria causing tetanus, botulism, and anthrax form endospores.

Bacterial Cell Interior

  • Nucleoid region: Contains the single, circular chromosome. May also contain plasmids, small, independently replicating DNA.
  • Ribosomes: Smaller than those of eukaryotes, differing in protein and RNA content. Some antibiotics target prokaryotic ribosomes.
  • Complex internal membranes: Invaginated regions of the plasma membrane function in respiration or photosynthesis.

Early Classification of Prokaryotes

  • Relied on staining characteristics and observable phenotypes.
  • Included photosynthetic or nonphotosynthetic, motile or nonmotile, and unicellular/colony/filamentous organisms; formation of spores or fission.
  • Important as human pathogens or not.

Molecular Classification

  • Used amino acid sequences of key proteins, nucleic acid hybridization (DNA/RNA mixing to see similarities), gene/RNA sequencing, and whole-genome sequencing to determine diversity.
  • Indicates diversity in bacteria and many bacteria are uncultured or unknown.

DNA Exchange through Horizontal Transmission

  • Conjugation: DNA transfer mediated by plasmids.
  • Transduction: DNA transfer mediated by viruses
  • Transformation: Direct uptake of DNA by a recipient cell from its environment

Bacterial Genetics

  • R or Resistance Plasmids: Encode antibiotic resistance genes, acquired through transposable elements.
  • Virulence plasmids: Encode genes for pathogenic traits. The E. coli O157:H7 strain arose this way.

Conjugation

  • F+ plasmids contain protein to assemble a pilus
  • The pilus binds to an F- cell to promote the transfer of DNA via a conjugation bridge.
  • Rolling-circle replication initiates the transfer, resulting in the recipient cell also becoming F+.

Integration and Excision of F plasmid

  • F plasmid can integrate into the bacterial chromosome via specific sites (regions of homology called insertion sequences)
  • Cells with the integrated F plasmid are called Hfr cells
  • During transfer some regions on the chromosome and plasmid can be transferred
  • The F plasmid can reverse the integration process to excise itself and may even pick up some of the chromosomal DNA to form an F′ plasmid. Transfer of F′ plasmids results in partial diploids.

Prokaryotic Metabolism

  • Autotrophs obtain energy by converting inorganic carbon into organic molecules.
  • Photoautotrophs: Examples are cyanobacteria, use light energy to drive photosynthesis as sulfur bacteria with anoxygenic photosynthesis.
  • Chemolithoautotrophs: Obtain energy from oxidizing inorganic substances (like ammonia or sulfur).
  • Heterotrophs obtain both carbon atoms and energy from organic molecules.
  • Photoheterotrophs: Use light as an energy source but obtain organic carbon from other organisms; purple and green nonsulfur bacteria are examples
  • Chemoheterotrophs: Obtain both energy and carbon from organic molecules; most prokaryotes are chemoheterotrophs as they are decomposers or pathogens.

Human Bacterial Disease

  • Infectious diseases were a significant cause of death in the early 20th century. Improved sanitation and antibiotics have dramatically reduced their impact.
  • Examples of bacterial diseases include TB, peptic ulcers (Helicobacter pylori), dental caries (Streptococcus), diphtheria, cholera.

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Prokaryotes - Chapter 23 (PDF)

Description

This quiz covers key concepts related to bacterial conjugation and the role of plasmids, including the F plasmid and R plasmids. It also explores prokaryotic cell structures and processes, enhancing understanding of genetic transfer and characteristics of bacterial and archaeal cells.

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