Prokaryotes: Locomotion and Surface Structures
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Questions and Answers

What is the process called when a prokaryotic cell takes up and incorporates foreign DNA from the surrounding environment?

  • Horizontal gene transfer
  • Transduction
  • Conjugation
  • Transformation (correct)

    • Prokaryotes can only obtain energy from light.

    False

    What is the term for the movement of genes among individuals from different species?

    Horizontal gene transfer

    In conjugation, a donor cell attaches to a recipient by a ______________, pulls it closer, and transfers DNA.

    <p>pilus</p> Signup and view all the answers

    Match the following prokaryotes with their modes of nutrition:

    <p>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</p> Signup and view all the answers

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

    <p>Nitrogen fixation</p> Signup and view all the answers

    Obligate anaerobes can survive with or without O2.

    <p>False</p> Signup and view all the answers

    Facultative anaerobes can survive with or without ___________________.

    <p>O2</p> Signup and view all the answers

    What type of archaea live in highly saline environments?

    <p>Extreme halophiles</p> Signup and view all the answers

    Chlamydia are Gram-positive bacteria.

    <p>False</p> Signup and view all the answers

    What is the byproduct of methanogens' metabolic process?

    <p>Methane</p> Signup and view all the answers

    Cyanobacteria are _______________ that generate O2.

    <p>photoautotrophs</p> Signup and view all the answers

    Match the following bacteria with their characteristics:

    <p>Proteobacteria = Gram-negative, include photoautotrophs, chemoautotrophs, and heterotrophs Chlamydia = Parasites that live only within animal cells Spirochetes = Helical heterotrophs</p> Signup and view all the answers

    What is the role of prokaryotes in the recycling of chemical elements?

    <p>They break down dead organisms and waste products</p> Signup and view all the answers

    Mycoplasms are the largest known cells.

    <p>False</p> Signup and view all the answers

    What is symbiosis in the context of ecology?

    <p>An ecological relationship in which two species live in close contact: a larger host and smaller symbiont</p> Signup and view all the answers

    What is the main function of fimbriae in prokaryotes?

    <p>To stick to their substrate or other individuals in a colony</p> Signup and view all the answers

    All prokaryotes have complex compartmentalization.

    <p>False</p> Signup and view all the answers

    What is the main component of bacterial flagella?

    <p>A motor, hook, and filament</p> Signup and view all the answers

    Many bacteria exhibit __________, the ability to move toward or away from a stimulus.

    <p>taxis</p> Signup and view all the answers

    What is the function of pili (or sex pili) in prokaryotes?

    <p>To exchange DNA</p> Signup and view all the answers

    Match the following terms with their functions:

    <p>Fimbriae = To stick to their substrate or other individuals in a colony Pili = To exchange DNA Flagella = To propel themselves Endospores = To survive harsh conditions</p> Signup and view all the answers

    Bacteria can reproduce sexually.

    <p>False</p> Signup and view all the answers

    What is the function of endospores in bacteria?

    <p>To survive harsh conditions</p> Signup and view all the answers

    What is the outermost layer of a bacterium that enables binding to cell surfaces and evasion of phagocytosis?

    <p>Capsule</p> Signup and view all the answers

    Gram-negative bacteria have a thick peptidoglycan layer and one cell membrane.

    <p>False</p> Signup and view all the answers

    What is the function of flagella in bacteria?

    <p>Flagella allow for bacterial movement.</p> Signup and view all the answers

    Bacteria can have different shapes, including coccus (circular), bacillus (rod-shaped), and _______________________.

    <p>spiral</p> Signup and view all the answers

    What is the function of pili in bacteria?

    <p>All of the above</p> Signup and view all the answers

    The plasma membrane of bacteria is impermeable, allowing no substances to enter or leave the cell.

    <p>False</p> Signup and view all the answers

    Match the following bacterial layers with their descriptions:

    <p>Capsule = A semi-permeable membrane that allows transportation of substances Plasma membrane = A semi-rigid structure that enables bacterial classification into gram-positive and gram-negative groups Cell wall = A polysaccharide-containing layer that enables binding to cell surfaces and evasion of phagocytosis</p> Signup and view all the answers

    Gram-positive bacteria have _______________________, which enables binding to cell walls and recognition by macrophages.

    <p>lipoteichoic acid</p> Signup and view all the answers

    What is the purpose of fixing cells to the slide in the Gram stain procedure?

    <p>to prepare the cell for staining</p> Signup and view all the answers

    What is the function of Graham's iodine in the Gram stain procedure?

    <p>to form a dye complex with crystal violet</p> Signup and view all the answers

    Why do Gram-positive bacteria retain the crystal violet iodine complex during the Gram stain procedure?

    <p>because they have a thick peptidoglycan layer</p> Signup and view all the answers

    What is the result of decolorization with ethanol on Gram-negative bacteria during the Gram stain procedure?

    <p>they lose the crystal violet iodine complex</p> Signup and view all the answers

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

    <p>to stain Gram-negative bacteria</p> Signup and view all the answers

    Why do Gram-negative bacteria lose the crystal violet iodine complex during the Gram stain procedure?

    <p>because they have a thin peptidoglycan layer</p> Signup and view all the answers

    What is the correlation between the Gram stain and the cell wall structure among bacteria?

    <p>Gram stain correlates with the cell wall structure among bacteria</p> Signup and view all the answers

    What is the result of adding ethanol to the slide during the Gram stain procedure?

    <p>it removes the crystal violet iodine complex from Gram-negative bacteria</p> Signup and view all the answers

    What is the primary reason for the evolution of 'super bugs'?

    <p>Overuse and misuse of antibiotics</p> Signup and view all the answers

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

    <p>It revolutionized medicine and saved millions of lives from infections</p> Signup and view all the answers

    What is the consequence of using broad-spectrum antibiotics?

    <p>They destroy beneficial microbes in the gut, leading to an imbalance in the microbiome</p> Signup and view all the answers

    What was the purpose of the Mega-Plate experiment?

    <p>To study the evolution of antibiotic resistance</p> Signup and view all the answers

    How do bacteria reproduce rapidly, leading to the evolution of antibiotic resistance?

    <p>Through a rapid process of cell division, allowing them to evolve resistance quickly</p> Signup and view all the answers

    What is the warning that Alexander Fleming gave regarding the use of antibiotics?

    <p>The misuse of antibiotics would make them ineffective against infections</p> Signup and view all the answers

    What is the result of antibiotic resistance spreading from animal populations to humans and crops?

    <p>It reduces the effectiveness of antibiotics against infections</p> Signup and view all the answers

    What is the significance of the Mega-Plate experiment's results?

    <p>It demonstrated that E. coli mutants evolved resistance to antibiotics in just 11 days</p> Signup and view all the answers

    Bacterial DNA exists in two parts: bacterial ______ and bacterial plasmid

    <p>chromosome</p> Signup and view all the answers

    The process of extracting a small part of the bacterial ______ to become a plasmid or reintegration of the plasmid into the bacterial ______ is called transposition

    <p>chromosome, chromosome</p> Signup and view all the answers

    In conjugation, F+ bacteria link with F- bacteria, creating a mating ______, and transfer a copy of their plasmid to the F- bacteria

    <p>bridge</p> Signup and view all the answers

    Transformation is the ability of bacteria to take up ______ DNA from the environment and use it

    <p>naked</p> Signup and view all the answers

    In transduction, a bacteriophage carrying its own DNA injects this DNA into a bacterial cell, and the viral DNA is integrated into the bacterial ______

    <p>DNA</p> Signup and view all the answers

    Lysogenic phage gives bacteria new abilities, such as producing ______

    <p>exotoxins</p> Signup and view all the answers

    What is the significance of the phylogenetic tree of life in relation to domains of life?

    <p>It shows the three main domains of life: Eukarya, Archaea, and Bacteria</p> Signup and view all the answers

    Domain Archaea and Eukarya are sister taxa, meaning they did not share a common ancestor.

    <p>False</p> Signup and view all the answers

    What are the types of environments where Archaea are typically found?

    <p>Extreme environments, such as high temperatures and high salinity. Examples include hot springs, the Dead Sea, and the Great Salt Lake.</p> Signup and view all the answers

    The domain _______________________ includes all single-celled prokaryotic organisms.

    <p>Bacteria</p> Signup and view all the answers

    Match the following groups of archaea with their characteristics:

    <p>Halophiles = extreme salt lovers Thermophiles = heat lovers Methanogens = methane producers</p> Signup and view all the answers

    What is the function of histones in Archaea and Eukarya?

    <p>To organize DNA</p> Signup and view all the answers

    Cyanobacteria are Gram-positive bacteria.

    <p>False</p> Signup and view all the answers

    What are some beneficial functions performed by domain Bacteria?

    <p>Nitrogen fixation and decomposition.</p> Signup and view all the answers

    What is the primary mechanism by which bacteria evolve resistance to antibiotics?

    <p>Mutations in the bacterial genome</p> Signup and view all the answers

    Why are broad-spectrum antibiotics problematic?

    <p>They can destroy beneficial microbes in the gut</p> Signup and view all the answers

    What was the purpose of the Mega-Plate experiment?

    <p>To study the evolution of antibiotic resistance</p> Signup and view all the answers

    What is the consequence of the misuse of antibiotics?

    <p>Destruction of beneficial microbes and increased susceptibility to infections</p> Signup and view all the answers

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

    <p>It revolutionized medicine and saved millions of lives</p> Signup and view all the answers

    How do bacteria spread antibiotic resistance?

    <p>Through horizontal gene transfer</p> Signup and view all the answers

    What was Alexander Fleming's warning regarding the use of antibiotics?

    <p>That they would lead to the evolution of resistant bacteria</p> Signup and view all the answers

    What is the result of the rapid reproduction of bacteria?

    <p>The quick spread of antibiotic resistance</p> Signup and view all the answers

    Study Notes

    Prokaryotic Characteristics

    • Prokaryotes have fimbriae, allowing them to stick to their substrate or other individuals in a colony
    • Pili (or sex pili) are longer than fimbriae and enable prokaryotes to exchange DNA

    Locomotion

    • Many bacteria exhibit taxis, the ability to move toward or away from a stimulus
    • Chemotaxis is the movement toward or away from a chemical stimulus
    • Most motile bacteria propel themselves using flagella, which are composed of a motor, hook, and filament

    Internal Organization

    • Prokaryotic cells usually lack complex compartmentalization
    • Some prokaryotes have in-foldings of the plasma membrane that perform metabolic functions
    • The genome consists of a circular chromosome located in the nucleoid region
    • Some species of bacteria also have smaller rings of DNA called plasmids

    Prokaryotic Reproduction

    • Prokaryotes reproduce by binary fission, with short generation times
    • Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries
    • Three factors contribute to genetic diversity in prokaryotes: rapid reproduction, mutation, and genetic recombination
    • Mutation rates during binary fission are low, but rapid reproduction allows mutations to accumulate rapidly in a population

    Domain Archaea

    • Archaea share certain traits with bacteria and other traits with eukaryotes
    • Some archaea live in extreme environments and are called 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 and produce methane as a waste product

    Domain Bacteria

    • Proteobacteria include photoautotrophs, chemoautotrophs, and heterotrophs
    • Chlamydia are parasites that live only within animal cells
    • Spirochetes are helical heterotrophs, with some being parasites
    • Cyanobacteria are photoautotrophs that generate O2
    • Gram-positive bacteria include Actinomycetes, Bacillus anthracis, Clostridium botulinum, and some Staphylococcus and Streptococcus

    Ecological Importance

    • Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems
    • Chemoheterotrophic prokaryotes function as decomposers, breaking down dead organisms and waste products
    • Prokaryotes can increase the availability of nitrogen, phosphorus, and potassium for plant growth

    Symbiosis and Genetic Recombination

    • Symbiosis is an ecological relationship in which two species live in close contact: a larger host and smaller symbiont
    • Genetic recombination occurs through transformation, transduction, and conjugation
    • Conjugation is the process where genetic material is transferred between prokaryotic cells

    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, and heterotrophs require an organic nutrient to make organic compounds
    • Energy and carbon sources are combined to give four major modes of nutrition
    • Nitrogen metabolism is essential for the production of amino acids and nucleic acids
    • In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)

    Bacteria Structure

    • Bacteria are the largest group of microorganisms with medical significance.
    • They come in three main shapes: coccus (circular), bacillus (rod-shaped), and spiral.
    • Other shapes include coca bacillus (in between coccus and bacillus) and vibrio (spiral and bacillus).

    Bacterial Movement and Appendages

    • Some bacteria have flagella, thin rigid filaments made of proteins, allowing for bacterial movement.
    • Hair-like appendages called fimbriae and pili are used for binding to cell surfaces and causing disease.
    • Pili are shorter than fimbriae but perform the same function.
    • Pili are also involved in bacterial conjugation, the transfer of genetic material between bacteria.

    Bacterial Layers

    • The outermost layer is the capsule, which has polysaccharides and enables binding to cell surfaces and evasion of phagocytosis.
    • The innermost layer is the plasma membrane, a semi-permeable membrane allowing transportation of substances in and out of the cell.
    • The plasma membrane is a phospholipid bilayer with proteins, similar to those found in human cells.
    • The cell wall is a semi-rigid structure that enables bacteria to be classified into gram-positive and gram-negative groups.

    Gram-Positive and Gram-Negative Bacteria

    • Gram-positive bacteria have a thick peptidoglycan layer and one cell membrane.
    • Gram-negative bacteria have a thin peptidoglycan layer and two cell membranes.
    • Gram-positive bacteria have lipoteichoic acid, which enables binding to cell walls and recognition by macrophages.
    • Gram-negative bacteria have lipid-like structures on the outer cell membrane, including lipoproteins and lipid A, which can cause diseases and shock syndromes.

    Cytoplasm and DNA

    • Cytoplasm contains water, enzymes, ribosomes, and circular DNA.
    • Ribosomes are the site of protein synthesis.
    • The DNA in bacteria is circular, unlike the linear DNA found in humans (except in mitochondria).
    • Plasmids are small, circular genetic information found in the cytoplasm, which can be incorporated into the circular DNA or transferred between bacteria through conjugation.

    Gram Stain Procedure

    • A thin film of cells from a fresh culture is prepared on a clean slide and allowed to dry.
    • Cells are fixed to the slide by brief heat fixation using a Bunsen burner flame.
    • The slide is stained with crystal violet for 30-40 seconds, resulting in all cells appearing purple under the microscope.
    • Excess crystal violet is removed by rinsing with water, and then the slide is treated with Graham's iodine for about one minute.
    • Decolorization is achieved by washing the slide with ethanol or acetone, which removes the crystal violet from Gram-negative bacteria but not from Gram-positive bacteria.
    • The ethanol or acetone is added drop-wise to the slide until the colour just starts to run clear.
    • Excess ethanol is washed off with water, and the slide is counter-stained with safranin for 20-30 seconds, which stains Gram-negative bacteria pink.

    Gram Stain Mechanism

    • The Gram stain method is based on the differences in bacterial cell wall structure.
    • In Gram-positive bacteria, the ethanol treatment shrinks the thick peptidoglycan layer, which retains the crystal violet iodine complex.
    • The thick peptidoglycan layer in Gram-positive bacteria acts as a permeability barrier, preventing the loss of the crystal violet iodine complex.
    • In Gram-negative bacteria, the thin peptidoglycan layer has large pores, allowing ethanol to extract lipids and increase porosity, resulting in the loss of the crystal violet iodine complex.

    Antibiotics and Microbes

    • Antibiotics are natural substances produced by microbes to kill other microbes, with a history of use spanning billions of years.
    • Alexander Fleming discovered antibiotics in 1928 by isolating penicillin from a contaminated bacterial culture.
    • Penicillin revolutionized medicine, saving millions of lives from infections.
    • Most commercial antibiotics are broad-spectrum, capable of destroying beneficial microbes in the gut, leading to microbiome imbalance.

    Problems with Antibiotics

    • Overuse and misuse of antibiotics have led to the evolution of resistant bacteria, also known as "super bugs."
    • Antibiotic resistance occurs when bacteria evolve to resist antibiotics, making them ineffective.
    • Misuse of antibiotics destroys beneficial microbes, increasing susceptibility to infections.

    The Mega-Plate Experiment

    • The Mega-Plate experiment involved growing E. coli bacteria in agar jelly with increasing concentrations of antibiotics.
    • The results showed that E. coli mutants evolved resistance to antibiotics in just 11 days.

    Evolution of Antibiotic Resistance

    • Bacteria reproduce rapidly, allowing them to evolve resistance quickly.
    • Exposure to antibiotics selects for bacteria with resistant mutations, leading to the spread of resistant microbes.
    • Antibiotic resistance can spread from animal populations to humans and crops.

    Fleming's Warning

    • Alexander Fleming warned that overusing antibiotics would lead to the evolution of resistant bacteria, making them ineffective against infections.
    • Fleming advocated for judicious use of antibiotics to prevent unintended consequences on the microbiome.

    Smart Use of Antibiotics

    • Antibiotics should only be used to treat bacterial diseases, not viral diseases.
    • Unnecessary antibiotic use leads to the evolution of resistant bacteria and disrupts the microbiome.
    • Wise and moderate use of antibiotics is essential to prevent the spread of antibiotic resistance.

    Bacterial Genetics

    • Bacterial DNA consists of two parts: a larger, more complex bacterial chromosome and a smaller bacterial plasmid that floats inside the bacteria.

    Transposition

    • Involves the extraction of a small part of the bacterial chromosome, which can become a plasmid or reintegrate into the chromosome.
    • Only affects plasmid DNA, not chromosome DNA.
    • Enables bacteria to share DNA with other bacteria through plasmid transfer.

    Conjugation

    • Occurs between F+ bacteria (possessing a sex pilus) and F- bacteria (lacking a sex pilus).
    • The sex pilus is encoded by the plasmid, not the chromosome.
    • F+ bacteria form a mating bridge with F- bacteria and transfer a copy of their plasmid, resulting in both bacteria becoming F+.

    Transformation (Competence)

    • The ability of certain bacteria to take up naked DNA from their environment and utilize it.
    • Allows bacteria to acquire new traits, such as antibiotic resistance.
    • Exclusively observed in Streptococcus pneumoniae, H.influenza, and Neisseria.
    • Requires the uptake of free DNA from the environment.

    Transduction

    • The process in which a bacteriophage (bacterial virus) injects its DNA into a bacterial cell.
    • The viral DNA integrates into the bacterial DNA and begins replicating.
    • Can result in bacterial death (lytic phage) or not (lysogenic phage).
    • Lysogenic phages can grant bacteria new capabilities, such as producing exotoxins.

    Phylogenetic Tree of Life

    • Emphasizes domain levels of organization, showing three main domains: Eukarya, Archaea, and Bacteria
    • Domain Eukarya and Archaea are sister taxa, sharing a common ancestor, despite differences in cellular structure

    Similarities between Archaea and Eukarya

    • Share RNA polymerase with multiple subunits
    • Have methionine as the start amino acid during protein synthesis
    • Possess histones, which organize DNA
    • These similarities suggest a closer evolutionary relationship between Archaea and Eukarya

    Domain Archaea

    • Found in extreme environments, such as high temperatures and high salinity
    • Examples include Halophiles, Thermophiles, and Methanogens
    • Five groups of archaea: URI Archaea and Crenarchaeota, among others

    Domain Bacteria

    • Includes all single-celled prokaryotic organisms
    • Found in almost every environment on earth
    • Perform beneficial functions: nitrogen fixation and decomposition
    • Can cause disease: stomach ulcers and Lyme disease

    Subdivisions of Domain Bacteria

    • Proteobacteria:
      • Alpha Proteobacteria (Rhizobium)
      • Beta Proteobacteria
      • Gamma Proteobacteria (Pseudomonas fluorescens)
      • Delta Proteobacteria
      • Epsilon Proteobacteria (Helicobacter pylori)
    • Chlamydiae:
      • Gram-negative bacteria that live within animal cells
      • Examples: Chlamydia trachomatis
    • Spirochetes:
      • Gram-negative bacteria with a helical shape
      • Examples: Borrelia and Treponema
    • Cyanobacteria:
      • Gram-negative bacteria that perform photosynthesis
      • Examples: Oscilloria
    • Gram-positive bacteria:
      • Examples: Bacillus and Staphylococcus

    Bacterial Diversity

    • Found in almost every environment on earth
    • Play important roles: nitrogen fixation and decomposition
    • Can cause disease, but many are harmless or beneficial to humans

    Antibiotics and Microbes

    • Antibiotics are natural substances produced by microbes to kill other microbes, with a history of use spanning billions of years.
    • Alexander Fleming discovered antibiotics in 1928 by isolating penicillin from a contaminated bacterial culture.
    • Penicillin revolutionized medicine, saving millions of lives from infections.
    • Most commercial antibiotics are broad-spectrum, capable of destroying beneficial microbes in the gut, leading to microbiome imbalance.

    Problems with Antibiotics

    • Overuse and misuse of antibiotics have led to the evolution of resistant bacteria, also known as "super bugs."
    • Antibiotic resistance occurs when bacteria evolve to resist antibiotics, making them ineffective.
    • Misuse of antibiotics destroys beneficial microbes, increasing susceptibility to infections.

    The Mega-Plate Experiment

    • The Mega-Plate experiment involved growing E. coli bacteria in agar jelly with increasing concentrations of antibiotics.
    • The results showed that E. coli mutants evolved resistance to antibiotics in just 11 days.

    Evolution of Antibiotic Resistance

    • Bacteria reproduce rapidly, allowing them to evolve resistance quickly.
    • Exposure to antibiotics selects for bacteria with resistant mutations, leading to the spread of resistant microbes.
    • Antibiotic resistance can spread from animal populations to humans and crops.

    Fleming's Warning

    • Alexander Fleming warned that overusing antibiotics would lead to the evolution of resistant bacteria, making them ineffective against infections.
    • Fleming advocated for judicious use of antibiotics to prevent unintended consequences on the microbiome.

    Smart Use of Antibiotics

    • Antibiotics should only be used to treat bacterial diseases, not viral diseases.
    • Unnecessary antibiotic use leads to the evolution of resistant bacteria and disrupts the microbiome.
    • Wise and moderate use of antibiotics is essential to prevent the spread of antibiotic resistance.

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