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Questions and Answers
Which characteristic is true about all archaea?
Which of the following is true about gram-positive bacteria?
What distinguishes proteobacteria from non-proteobacteria?
What is a significant feature of bacteroides bacteria?
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Which of the following statements about cyanobacteria is correct?
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Which bacterial group is known for having a high number of pathogenic species?
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What is a common trait of extremophiles?
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Which of the following best describes the classification of spirochetes?
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Which of the following bacteria is responsible for syphilis?
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Which type of bacteria are Bacteroides classified as?
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What unique feature allows spirochetes to move through tissues?
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Which electron donor do purple sulfur bacteria use for photosynthesis?
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What is a characteristic of purple non-sulfur bacteria?
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Which of the following diseases is NOT caused by spirochetes?
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What role do Bacteroides play in the human colon?
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What common characteristic do all obligate anaerobes share?
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What type of bacteria are Staphylococcus and Streptococcus classified as?
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Which of the following is an example of a pathogenic streptococcus?
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Which hemolytic activity is displayed by Staphylococcus aureus?
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What type of toxin does S. aureus produce?
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What method is used to categorize species of Enterococcus, Streptococcus, and Staphylococcus?
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Which of the following describes Actinobacteria?
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What is a distinguishing feature of the cell wall in Actinobacteria?
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Which enzyme produced by pathogenic streptococci can lyse red blood cells?
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What is the infective form of Chlamydia known as an elementary body primarily characterized by?
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Which of the following correctly describes the prokaryotic domain composed of organisms that can tolerate extreme environments?
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What method do spirochetes primarily use for motility?
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What distinguishes Chlamydophila psittaci in its pathogenicity?
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Which group of bacteria is recognized for their ability to fix nitrogen in the ecosystem?
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Which of the following lists groups of bacteria based on their photosynthetic capabilities?
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What is a key characteristic of the family Enterobacteriaceae?
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What is the primary electron donor used by green sulfur bacteria during their photosynthesis?
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Which of the following accurately describes cyanobacteria?
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In terms of bacterial classification, what defines proteobacteria?
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What type of disease does Corynebacterium diphtheriae cause?
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Which organism is known for producing most antibiotics?
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Which characteristic is associated with Mycobacterium tuberculosis?
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What kind of environment do extreme halophiles require?
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Which of the following statements about Mycobacterium leprae is correct?
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Which type of bacteria are classified as anaerobic extremophiles?
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What type of cell wall do archaea have?
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What distinguishes Streptomyces from other actinobacteria?
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Study Notes
Prokaryote Classification
- Bacteria and Archaea are the two domains of prokaryotes.
- Bacteria were the first living organisms.
- Archaea evolved in a pre-oxygen atmosphere.
- Gram-negative bacteria evolved first, then gram-positive bacteria.
- All archaea are extremophiles and obligate anaerobes.
- Bacteria can be aerobic or anaerobic.
- Bacteria have a wider range of environmental niches.
- Archaea, unlike bacteria, are non-pathogenic.
Bacterial Shapes and Arrangements
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Major Bacterial Groups:
- Bacteroides: Gram-negative rods, obligate anaerobes.
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Photosynthetic Bacteria:
- Anoxygenic: Sulfur/non-sulfur (purple/green), use an electron donor that is not water.
- Cyanobacteria: Oxygenic, use water as an electron donor and produce oxygen.
- Spirochetes: Coiled, move via axial filaments (endoflagella), many are pathogenic.
- Chlamydias: Intracellular parasitic bacteria.
- Gram-Positive Bacteria: Latest evolving bacteria, divided into the Firmicutes and Actinobacteria phyla.
Non-Proteobacteria
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Bacteroides:
- Bacteroides fragilis: Gram-negative rod, obligate anaerobe, normal colon microbiota.
- First bacteria to evolve.
- Major inhabitants of the human colon.
- Ferment indigestible sugar derivatives.
- Break down toxins.
- Produce communication molecules (polysaccharide A) that direct the innate immune response.
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Photosynthetic Bacteria:
- Anoxygenic: Carry out photosynthesis using a non-water electron donor.
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Purple Sulfur Bacteria:
- Use H2S as the electron donor.
- Produce sulfides instead of oxygen.
- Absorb higher energy wavelengths than green sulfur bacteria.
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Purple Non-Sulfur Bacteria:
- Use organic hydrogen sources as the electron donor.
- Absorb higher energy wavelengths than green non-sulfur bacteria.
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Green Sulfur Bacteria:
- Use H2S as the electron donor for photosynthesis.
- Produce sulfides instead of oxygen.
- Aerotolerant anaerobes.
- Absorb light at lower wavelengths than purple sulfur bacteria.
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Green Non-Sulfur Bacteria:
- Use organic hydrogen sources as the electron donor.
- Aerotolerant anaerobes.
- Absorb lower wavelengths than purple non-sulfur bacteria.
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Spirochetes:
- Spiral-shaped bacteria.
- Coiled and move via axial filaments.
- Many are pathogenic:
- Treponema pallidum: Causes syphilis.
- Treponema pertenue: Causes yaws.
- Treponema pallidum subspecies endemicum: Causes bejel.
- Can literally "drill" through skin and tissues.
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Chlamydia:
- Obligate intracellular parasites.
- Diminished or no cell wall.
- Grow intracellularly.
- Elementary Bodies: The "endospore-like" infective form.
- Reticulate Bodies: The intracellular replicative, cellular form.
- Chlamydia trachomatis: Causes pelvic inflammatory disease and urethritis.
- Chlamydophila psittaci: Causes respiratory psittacosis (pneumonia).
Proteobacteria
- All gram-negative bacteria.
- Oxygen-tolerant.
- Most are obligate aerobes or facultative anaerobes.
- Great diversity (over 30% of known bacteria).
- The largest bacterial phyla.
- Diverse metabolisms, including heterotrophs, lithotrophs, and photosynthesizers.
- Five classes: alpha, beta, gamma, delta, epsilon.
- Include oxygenic and anoxygenic photosynthetic bacteria:
- Cyanobacteria: Oxygenic, use water as the electron donor and produce oxygen.
- Green Sulfur/Non-Sulfur Bacteria: Anoxygenic, use a non-water electron donor.
- Many pathogenic species (Shigella, Salmonella).
- Contain nitrogen-fixing species.
Cyanobacteria
- Also known as "blue-green algae."
- Oxygenic photosynthetic bacteria.
- Use water as the electron donor and produce oxygen.
- Fix the majority of carbon dioxide in the ecosystem.
- Many contain heterocysts that fix nitrogen.
- Many contain gas vesicles that provide buoyancy.
- Can be unicellular or filamentous, and colonial.
Enterobacteriaceae
- A family of enteric (gut) gram-negative rods.
- All are facultative anaerobes and motile.
- E. coli, an example, uses actin-like filaments to propel itself through host cytoplasm and invade neighboring cells.
Gram-Positive Bacteria: Firmicutes
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Low "GC content" gram-positive bacteria.
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Streptococcus:
- Coccus in chains.
- Produce enzymes that destroy tissues.
- Pathogenic streptococci include:
- Streptococcus pneumoniae: Causes pneumonia.
- Streptococcus mutans: Causes dental caries.
- Beta-hemolytic streptococci hemolyze blood.
- Streptococcus pyogenes: Causes strep throat and scarlet fever.
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Staphylococcus:
- Grape-like clusters.
- Often antibiotic-resistant.
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Staphylococcus aureus: Causes wound and skin infections, produces four types of toxins:
- Hemolysin: Lyses red blood cells.
- Leukotoxin: Lyses white blood cells.
- Enterotoxin: Intestinal toxin.
- Toxic-shock syndrome toxin-1: Can cause sepsis.
- Species of Enterococcus, Streptococcus, and Staphylococcus are distinguished by their level of hemolysis on blood agar plates.
Gram-Positive Bacteria: Actinobacteria
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High "GC content" gram-positive bacteria.
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A broad group, including antibiotic producers, decomposers, and pathogens.
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Cell wall includes unusual cell wall lipids, such as mycolic acid.
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Most stain with acid-fast stain.
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Corynebacterium:
- Corynebacterium diphtheriae: Causes diphtheria, characterized by difficulty breathing, heart failure, and paralysis.
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Propionibacterium:
- Produces propionic acid.
- Propionibacterium acnes: Causes acne.
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Gardnerella:
- Gardnerella vaginalis: Causes vaginitis.
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Streptomyces:
- The largest genus of Actinobacteria.
- Most produce endospores.
- Isolated from soil.
- Produce the majority of antibiotics.
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Mycobacterium:
- Acid-fast bacteria.
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Mycobacterium tuberculosis:
- Mycolic acid cell wall: Makes it an intracellular pathogen.
- Highly infective obligate aerobe: Infects the lungs.
- Highly contagious: Spread through aerosol transmission.
- Many infections are antibiotic resistant.
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Mycobacterium leprae:
- Mycolic acid cell wall: Makes it an intracellular pathogen.
- Causes leprosy: Infects peripheral nerves.
- Targets skin, eyes, nose, and mouth.
- Not highly contagious: Spread through direct contact.
Archaea
- Often referred to as "extreme bacteria," all are anaerobic extremophiles.
- Unique cell wall: Pseudomurein, which lacks peptidoglycan.
- Heterotrophic: Require organic and inorganic carbon for metabolism.
- Non-pathogenic: No species has been shown to cause human disease.
- Environmental niche: Extreme environments, including the human gut.
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Extremophiles:
- Extreme Halophiles: Require a salt concentration of over 25%.
- Thermophiles: Require a growth temperature over 80°C.
- Psychrophiles: Require low temperatures.
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Description
Test your knowledge about the two domains of prokaryotes: Bacteria and Archaea. Explore the evolution, characteristics, and classification of various bacterial groups and their distinctive features. This quiz covers topics such as bacterial shapes, arrangements, and metabolic types.