Genetic Recombination in Prokaryotes

Questions and Answers

What is the process by which genetic material is transferred between prokaryotic cells?

Conjugation (correct)

Transduction

Horizontal Gene Transfer

Transformation

Which of the following is an example of horizontal gene transfer?

Gene transfer through transformation

Gene transfer from one bacterium to another through a virus

Gene transfer between different species of bacteria (correct)

Gene transfer from parent to offspring

What is the term for the process by which some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)?

Nitrogen assimilation

Nitrogen reduction

Nitrogen fixation (correct)

Nitrogen metabolism

Which of the following prokaryotes require oxygen for cellular respiration?

Obligate aerobes Signup and view all the answers

What is the term for the process by which a prokaryotic cell takes up and incorporates foreign DNA from the surrounding environment?

Transformation Signup and view all the answers

Which of the following is an example of a nutrient source for heterotrophs?

Organic compounds Signup and view all the answers

What is the term for the exchange of genetic material between bacteria through the agency of viruses?

Transduction Signup and view all the answers

Which of the following is a characteristic of obligate anaerobes?

They are poisoned by oxygen and use fermentation or anaerobic respiration Signup and view all the answers

What is the primary function of chemoheterotrophic prokaryotes in ecosystems?

To break down dead organisms and waste products Signup and view all the answers

What is the term for archaea that thrive in very hot environments?

Extreme thermophiles Signup and view all the answers

Which type of bacteria is known for being the smallest known cells?

Mycoplasms Signup and view all the answers

What is the primary difference between methanogens and other archaea?

Their ability to produce methane Signup and view all the answers

What is the term for the process by which prokaryotes increase the availability of nitrogen, phosphorus, and potassium for plant growth?

Chemical recycling Signup and view all the answers

Which type of bacteria is known for causing syphilis?

Treponema Signup and view all the answers

What is the term for archaea that live in highly saline environments?

Extreme halophiles Signup and view all the answers

Which type of bacteria is known for being photoautotrophs that generate O2?

Cyanobacteria Signup and view all the answers

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

To provide structural support and maintain cell shape Signup and view all the answers

What is the main difference between Gram-positive and Gram-negative bacteria?

The amount of peptidoglycan in their cell walls Signup and view all the answers

What is the primary mechanism of generating genetic diversity in bacteria?

Horizontal gene transfer Signup and view all the answers

What is the primary source of energy for most prokaryotes?

Organic compounds Signup and view all the answers

What is the function of a capsule in prokaryotes?

To protect the cell from antibiotics and the host immune system Signup and view all the answers

What is the primary difference between prokaryotic and eukaryotic cell walls?

The presence or absence of peptidoglycan Signup and view all the answers

What is the purpose of the Gram stain in microbiology?

To classify bacteria based on cell wall composition Signup and view all the answers

What is the primary function of plasmid DNA in prokaryotes?

To confer antibiotic resistance Signup and view all the answers

What is the main function of fimbriae and pili in bacteria?

To bind to cell surfaces and contribute to disease causation Signup and view all the answers

What is the composition of the innermost layer of a bacterium?

A phospholipid bilayer with proteins Signup and view all the answers

What is the primary difference between gram-positive and gram-negative bacteria?

The thickness of the peptidoglycan layer Signup and view all the answers

What is the function of lipoteichoic acid in gram-positive bacteria?

To recognize and bind to macrophages Signup and view all the answers

What is the purpose of the Gram stain in microbiology?

To distinguish between gram-positive and gram-negative bacteria Signup and view all the answers

What is the function of the cell wall in bacteria?

To provide structural support and maintain cell shape Signup and view all the answers

What is the composition of the outer cell membrane in gram-negative bacteria?

A layer of lipid-like structures, including lipoproteins and lipid A Signup and view all the answers

What is the function of the capsule in bacteria?

To enable binding to cell surfaces and evade phagocytosis Signup and view all the answers

What is the primary reason why fresh cultures are used in the Gram stain procedure?

Because aged cells lose their ability to retain the stain Signup and view all the answers

What is the purpose of adding Gram's iodine in the Gram stain procedure?

To combine with crystal violet to form a dye complex Signup and view all the answers

What is the role of the thick peptidoglycan layer in Gram positive cells?

To prevent the loss of the crystal violet iodine complex Signup and view all the answers

What is the effect of ethanol on the peptidoglycan layer in Gram positive cells?

It shrinks the thick peptidoglycan layer, retaining the dye Signup and view all the answers

What is the purpose of adding safranin in the Gram stain procedure?

To stain Gram negative bacteria pink Signup and view all the answers

What is the primary difference between Gram positive and Gram negative bacteria in terms of their cell wall structure?

The thickness of the peptidoglycan layer Signup and view all the answers

What is the primary mechanism by which antibiotics kill bacteria?

By disrupting the bacterial cell wall Signup and view all the answers

What is the consequence of overusing antibiotics in livestock?

The development of antibiotic-resistant bacteria Signup and view all the answers

What is the purpose of Alexander Fleming's discovery of penicillin?

To revolutionize medicine and treat bacterial infections Signup and view all the answers

What is the Mega-Plate Experiment designed to study?

The evolution of antibiotic resistance in bacteria Signup and view all the answers

What is a common misuse of antibiotics?

Using them to treat viral infections Signup and view all the answers

What can contribute to the development of antibiotic-resistant bacteria?

All of the above Signup and view all the answers

What is a characteristic of Alexander Fleming's view of bacteria?

He recognized that bacteria can be beneficial Signup and view all the answers

What is a consequence of the overuse of antibiotics?

The rise of malevolent microbes like Salmonella and Clostridium difficile Signup and view all the answers

Which of the following processes involves the direct transfer of DNA between bacteria through a mating bridge?

Conjugation Signup and view all the answers

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

To encode for the bacterial sex pilus Signup and view all the answers

Which of the following types of phages can give bacteria 'superpowers'?

Lysogenic phages Signup and view all the answers

What is the primary difference between the bacterial chromosome and the plasmid?

The plasmid is smaller than the chromosome Signup and view all the answers

Which of the following processes is exclusive to Streptococcus pneumoniae, H. influenzae, and Neisseria?

Transformation Signup and view all the answers

What is the primary mechanism of DNA transfer in transduction?

Injection of viral DNA into the bacterial chromosome Signup and view all the answers

Which of the following is a result of transposition?

The integration of plasmid DNA into the bacterial chromosome Signup and view all the answers

What is the primary function of the bacterial plasmid in genetic transfer?

To facilitate the exchange of genetic material between bacteria Signup and view all the answers

What is the characteristic that distinguishes Domain Bacteria from the other two domains of life?

Circular chromosomes Signup and view all the answers

Which of the following is a characteristic shared by Domain Eukarya and Domain Archaea?

Linear chromosomes with telomeres Signup and view all the answers

What is the term for the subdivision of Archaea that includes thermophiles?

Crenarchaeota Signup and view all the answers

Which of the following is an example of a domain that is found in almost every environment on Earth?

Domain Bacteria Signup and view all the answers

What is the term for the process by which Domain Eukarya and Domain Archaea share a common ancestor?

Sister taxa Signup and view all the answers

Which of the following is a characteristic unique to Domain Archaea?

Ability to thrive in extreme environments Signup and view all the answers

What is the term for the type of RNA polymerase found in Domain Eukarya and Domain Archaea?

Different type Signup and view all the answers

Which of the following is an example of a methanogen?

Methane-producing archaeon Signup and view all the answers

Study Notes

Genetic Recombination

Prokaryotic cells can take up and incorporate foreign DNA from the surrounding environment through transformation
Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)
Horizontal gene transfer is the movement of genes among individuals from different species
Conjugation is the process where genetic material is transferred between prokaryotic cells, requiring a pilus and the F factor for DNA transfer

Metabolism and Nutrition

Prokaryotes can be categorized by how they obtain energy and carbon:
- Phototrophs obtain energy from light
- Chemotrophs obtain energy from chemicals
- Autotrophs require CO2 as a carbon source
- Heterotrophs require an organic nutrient to make organic compounds
Energy and carbon sources combine to give four major modes of nutrition
Nitrogen is essential for the production of amino acids and nucleic acids
Nitrogen fixation: some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)
Cyanobacterium Anabaena has photosynthetic cells and nitrogen-fixing cells called heterocysts that exchange metabolic products

Prokaryotic Diversity

Domain Archaea:
- Share traits with bacteria and eukaryotes
- Some live in extreme environments (extremophiles)
- Extreme halophiles (Clade Euryarchaeota) live in highly saline environments
- Extreme thermophiles (Clade Crenarchaeota) thrive in very hot environments
- Methanogens (Clade Euryarchaeota) live in swamps and marshes, producing methane as a waste product, and are strict anaerobes poisoned by O2
Domain Bacteria:
- Proteobacteria: gram-negative, include photoautotrophs, chemoautotrophs, and heterotrophs, some anaerobic and others aerobic
- Chlamydia: parasites that live only within animal cells
- Spirochetes: helical heterotrophs, some parasitic
- Cyanobacteria: photoautotrophs that generate O2
- Gram-positive bacteria: include Actinomycetes, Bacillus anthracis, Clostridium botulinum, Staphylococcus, Streptococcus, and Mycoplasms

Ecological Importance

Prokaryotes play a major role in chemical recycling, decomposing dead organisms and waste products
Chemoheterotrophic prokaryotes increase the availability of nitrogen, phosphorus, and potassium for plant growth
Symbiosis: an ecological relationship between a larger host and smaller symbiont, such as bacteria and Archaea

Bacterial Structure

Bacteria come in three main shapes: coccus (circular), bacillus (rod-shaped), and spiral.

Flagella and Hair-Like Appendages

Flagella are thin, rigid filaments that enable bacterial movement by propelling the bacteria forward or moving it around.
Fimbriae and pili are hair-like appendages used for binding to cell surfaces, contributing to disease causation, and bacterial conjugation.

Layers of a Bacterium

The capsule is the outermost layer, containing polysaccharides that enable binding to cell surfaces and avoid phagocytosis.
The plasma membrane is a semi-permeable membrane allowing transportation of substances in and out of the cell, similar in bacteria and humans, consisting of a phospholipid bilayer with proteins.
The cell wall is a complex, semi-rigid structure that enables classification into gram-positive and gram-negative bacteria.

Cell Wall Composition

Gram-positive bacteria have a thick peptidoglycan layer above the cell membrane and lipoteichoic acid, which enables binding to cell walls and recognition by macrophages.
Gram-negative bacteria have a thin peptidoglycan layer, an extra outer cell membrane, and lipid-like structures (lipoproteins and lipid A) that can cause diseases and shock syndromes.

Gram Staining

Gram staining is used to classify bacteria based on cell wall composition, involving crystal violet, iodine, decolorization with alcohol, and safranin.
Gram-positive bacteria stain purple, while gram-negative bacteria stain pinkish-red.

Cytoplasm

Cytoplasm contains water, enzymes, ribosomes, and circular DNA.
Ribosomes are the site of protein synthesis and are found throughout the cytoplasm.
Bacterial DNA is circular, unlike the linear DNA found in eukaryotes (except for mitochondrial DNA).
Plasmids are small, circular genetic materials found in the cytoplasm, which can be incorporated into the main DNA or transferred between bacteria through conjugation.

Gram Stain Procedure

Fresh cultures are required for Gram staining, as aged cells lose their ability to retain the stain
Cells are prepared on a slide by drying and fixing with a Bunsen burner flame
Crystal violet stain is applied for 30-40 seconds, followed by a rinse with water
Gram's iodine solution combines with crystal violet to form a dye complex
Decolorization is achieved with ethanol or acetone, which removes the dye complex from Gram negative bacteria
Decolorization is stopped when the drop coming off the edge of the slide becomes colorless
A counter stain of safranin is used to stain Gram negative bacteria pink

Mechanism of Gram Stain

The Gram stain is correlated with bacterial cell wall structure
Thick peptidoglycan layer in Gram positive cells acts as a permeability barrier, retaining the crystal violet iodine complex
Ethanol shrinks the thick peptidoglycan layer, allowing it to retain the dye
Thin peptidoglycan layer in Gram negative cells has large pores, allowing ethanol to extract lipids and increase porosity, removing the crystal violet iodine complex

Antibiotics and Bacteria

Antibiotics are natural substances produced by microbes to kill other microbes, used for billions of years.

The Discovery of Penicillin

Alexander Fleming discovered penicillin in 1928 by accident when a mold landed in one of his bacterial cultures.
He isolated the chemical and called it penicillin, revolutionizing medicine and saving millions of lives from infections.

The Dark Side of Antibiotics

Most commercial antibiotics destroy not only bad bacteria but also many other microbes living in the gut.
This leads to the growth of malevolent microbes like Salmonella, Campylobacter, and Clostridium difficile.

The Problem of Antibiotic Misuse

Antibiotic misuse creates invincible super bugs, bacteria that have evolved to resist antibiotics.
Overuse of antibiotics drives the evolution of resistant bacteria, making them less effective against infections.

The Mega-Plate Experiment

Scientists Michael Baym, Tami Lieberman, and Roy Kishony studied antibiotic resistance using a giant petri dish.
They grew E.coli bacteria on the dish, introducing different concentrations of antibiotics to observe resistance evolution.
The bacteria evolved super resistance to antibiotics in just 11 days.

Consequences of Antibiotic Overuse

Antibiotics are often misused to treat viral diseases like colds and flu, which they are ineffective against.
Overuse of antibiotics leads to the growth of resistant bacteria in livestock, spreading to humans.
Antibacterial chemicals in soaps, hand gels, and toys contribute to the problem.

Alexander Fleming's Legacy

Fleming appreciated the beauty of bacteria, creating germ art using microbes as his medium.
He recognized that bacteria could be helpful and were everywhere.

Bacterial Genetics

Bacterial DNA is composed of two parts: the larger, complex bacterial chromosome and the smaller bacterial plasmid
The bacterial chromosome contains most of the bacterial DNA, while the plasmid is a smaller, separate piece of DNA that floats inside the bacteria

Transposition

Involves the extraction of a small part of the bacterial chromosome to become a plasmid or the reintegration of a plasmid into the bacterial chromosome
Plasmids play a crucial role in this process due to their small size and accessibility
Bacteria can only share their plasmid, not their chromosome, with other bacteria

Conjugation

F+ bacteria have a sex pilus, encoded by their plasmid, which allows them to form a mating bridge with F- bacteria
F+ bacteria transfer a copied plasmid, encoding for the sex pilus, to F- bacteria
Both bacteria then have a plasmid encoding for a sex pilus and become F+
Conjugation allows for the horizontal transfer of genetic material between bacteria

Transformation

This process, also known as competence, enables bacteria to take up naked DNA or genomes from their environment and utilize it
Bacteria can acquire antibiotic resistance genes from their environment and become antibiotic resistant
Only certain species, such as Streptococcus pneumoniae, H.influenza, and Neisseria, are capable of transformation

Transduction

Occurs when a bacteriophage (bacterial virus) injects its own DNA into the bacterial DNA
The viral DNA is integrated into the bacterial DNA and begins replicating the virus
Lytic phages kill the bacteria, while lysogenic phages do not and can confer "superpowers" on the bacteria
Lysogenic phages can enable bacteria to produce exotoxins

Domain of Life: Phylogenetic Tree

The phylogenetic tree represents three main domains of life: Eukarya, Archaea, and Bacteria
Eukarya and Archaea share a common ancestor, forming a sister taxa relationship
Bacteria is distinct from Eukarya and Archaea

Similarities between Archaea and Eukarya

Both have RNA polymerase, but with different types
Both use methionine as the start amino acid during protein synthesis
Both have histones, proteins that organize DNA
Both have linear chromosomes with telomeres

Domain Archaea

Found in extreme environments, such as hot springs, salt lakes, and deep-sea vents
Includes Halophiles (salt-loving), Thermophiles (heat-loving), and Methanogens (methane-producing)
Subdivided into Crenarchaeota (thermophiles) and Euryarchaeota (methanogens and halophiles)

Domain Bacteria

Found in almost every environment on Earth, including soil, water, and human skin
Includes Proteobacteria, Chlamydia, Spirochetes, Cyanobacteria, and Gram-positive bacteria
Subdivided into Alpha Proteobacteria, Beta Proteobacteria, Gamma Proteobacteria, Delta Proteobacteria, and Epsilon Proteobacteria

Bacterial Diversity and Ecological Impact

Play a crucial role in ecosystems, including nitrogen fixation, decomposition, and primary production
Responsible for diseases, such as tuberculosis, syphilis, and Lyme disease

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Description

This quiz covers various ways genetic material is transferred between prokaryotic cells, including transformation, transduction, and conjugation. It explains the role of bacteriophages and horizontal gene transfer.