Questions and Answers
Which of the following are main ways that bacteria are classified? (Select all that apply)
What is a bacteria?
A prokaryotic single cell organism lacking a membrane-bound nucleus.
What are Rickettsiae?
Parasitic bacteria that are obligate intracellular parasites.
What are Chlamydiae?
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What are the most common Gram positive bacteria?
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Name some clinically important Gram positive cocci: Staphylococci, __________, Enterococci.
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Name some clinically important Gram positive bacilli: Clostridia, __________, Listeria.
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Name some clinically important Gram negative cocci: __________.
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Name some clinically important Gram negative bacilli: Enterobacteria, __________.
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How can bacteria be classified according to their relationship with oxygen?
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What are filamentous bacteria that can't be easily detected with standard Gram staining?
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Study Notes
Bacterial Classification Methods
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Gram Staining: Differentiates bacteria based on cell wall structure.
- Gram Positive: Thick peptidoglycan wall, retains crystal violet, appears purple/violet.
- Gram Negative: Thin cell wall, does not retain crystal violet, appears red/pink after counterstaining with safranin.
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Morphology: Classification based on bacterial shape:
- Cocci: Spherical bacteria.
- Bacilli: Rod-shaped bacteria.
- Spirilla: Spiral-shaped bacteria.
Definition of Bacteria
- Bacteria are prokaryotic organisms (single-celled), lacking a membrane-bound nucleus.
- Contain DNA and RNA; capable of independent metabolic processes, including ATP synthesis.
Rickettsiae
- Parasitic bacteria that act as obligate intracellular parasites.
- Size between viruses and classical bacteria.
- Typically transmitted by arthropod vectors, such as ticks (example: Typhus).
- Detection methods include serology and PCR.
Chlamydiae
- Very small intracellular parasites, smaller than some viruses.
- Unable to synthesize ATP and invisible under a light microscope.
- Difficult to culture; serology and PCR are necessary for identification.
- Associated with atypical pneumonia and sexually transmitted diseases.
Common Gram Positive Bacteria
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Hemolytic Types:
- Alpha Hemolytic: Incomplete lysis of red blood cells.
- Beta Hemolytic: Complete lysis of red blood cells.
Common Gram Negative Bacteria
- Not specifically listed but includes various clinically significant groups.
Clinically Important Gram Positive Cocci
- Staphylococci: Arranged in clusters.
- Streptococci: Arranged in chains.
- Enterococci: Associated with biliary and intra-abdominal sepsis.
Clinically Important Gram Positive Bacilli
- Clostridia: Species such as tetani (tetanus), botulinum (botulism), and difficile (C. difficile colitis).
- Bacillus: Includes anthracis (anthrax).
- Corynebacterium: Responsible for diphtheria.
- Listeria monocytogenes: Can cause meningoencephalitis in neonates and immunocompromised individuals.
Clinically Important Gram Negative Cocci
- Neisseria: Includes meningitidis (meningitis) and gonorrhoeae (gonorrhea).
Clinically Important Gram Negative Bacilli
- Enterobacteria: Includes pathogenic strains such as E.coli, Klebsiella, Salmonella, Shigella, and Proteus.
- Helicobacter: Associated with gastric infections.
- Pseudomonas: Known for its resistance to antibiotics.
- Bacteroides: Part of the normal gut flora, can cause infections.
- Coccobacilli: Includes Haemophilus (causing meningitis) and Moraxella (linked to COPD exacerbations).
- Legionella: Associated with pneumonia outbreaks.
Oxygen Relationship Classification
- Anaerobic Bacteria: Cannot detoxify oxygen, reliant on anaerobic metabolism.
- Facultative Anaerobes: Prefer oxygen for more efficient metabolism but can survive anaerobically.
- Example genera:
- Gram Positive: Clostridium (spore-forming), Actinomyces (facultative, filamentous).
- Gram Negative: Bacteroides, Acinetobacter.
Bacteria Resistant to Standard Gram Staining
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Filamentous Bacteria: May produce mycelium and resist gram staining.
- Actinomyces israelii: Causes subcutaneous infections.
- Mycobacteria: Includes pathogens such as Mycobacterium tuberculosis and leprosy; have a waxy coat that resists staining.
- Mycoplasma: Lacks a cell wall, associated with atypical pneumonia.
- Spirochetes: Corkscrew-shaped bacteria with double membranes, includes Treponema pallidum (syphilis) and Leptospira (Leptospirosis).
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Description
This quiz focuses on the classification of bacteria through key methods such as Gram staining and morphology. Test your knowledge on identifying different types of bacteria based on their characteristics. Perfect for students of microbiology or anyone interested in the life sciences.
