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Questions and Answers
Which group of bacteria is classified as having a flexible cell wall?
Which group of bacteria is classified as having a flexible cell wall?
Which type of bacteria lack a cell wall?
Which type of bacteria lack a cell wall?
Which of the following is a characteristic of Gram-negative bacteria?
Which of the following is a characteristic of Gram-negative bacteria?
Which of the following bacteria is classified as Gram-positive?
Which of the following bacteria is classified as Gram-positive?
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Whichbacterium is classified as a Spirochete?
Whichbacterium is classified as a Spirochete?
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Which of the following is true about Gram-positive bacteria?
Which of the following is true about Gram-positive bacteria?
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Which bacteria is an example of a Gram-negative cocci?
Which bacteria is an example of a Gram-negative cocci?
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What type of organisms are classified as acellular?
What type of organisms are classified as acellular?
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Which of the following characteristics distinguishes prokaryotes from eukaryotes?
Which of the following characteristics distinguishes prokaryotes from eukaryotes?
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Which of the following is an example of a prokaryotic organism?
Which of the following is an example of a prokaryotic organism?
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What is the primary method of reproduction for prokaryotic organisms?
What is the primary method of reproduction for prokaryotic organisms?
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What type of ribosome is found in eukaryotic cells?
What type of ribosome is found in eukaryotic cells?
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In which morphological arrangement would you classify Staphylococcus aureus?
In which morphological arrangement would you classify Staphylococcus aureus?
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Which bacteria are known for having a curved or comma shape?
Which bacteria are known for having a curved or comma shape?
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Which characteristic is NOT associated with eukaryotic cells?
Which characteristic is NOT associated with eukaryotic cells?
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Study Notes
Lecture 1: Introduction to Medical Microbiology
- Covered by Dr. Rasha Mokhtar Elnagar, Associate Professor of Medical Microbiology & Immunology
- Defined microbiology as the study of microorganisms that can't be seen without a microscope.
- Defined micro as very small, requiring a microscope to view.
- Biology is the study of living organisms.
Definitions
- Microbiology is the science of studying microorganisms.
- Microorganisms include bacteria, viruses, fungi, protozoa, and helminths.
Classification of Microorganisms
- Microorganisms are classified as either acellular or cellular.
- Acellular microorganisms are not cells and lack a cell membrane. They reproduce inside a living cell. Viruses are an example.
- Cellular microorganisms have a cell membrane. Cellular organisms are prokaryotic (lacking a nucleus and membrane-bound organelles) or eukaryotic (having a nucleus and membrane-bound organelles).
- Prokaryotes include bacteria.
- Eukaryotes include protozoa, fungi, and helminths.
Classification of Bacteria
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Bacteria are classified by morphology (shape and arrangement), staining reaction (Gram stain, acid-fast stain), and cell wall structure.
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Morphology:
- Cocci: spherical or oval cells (e.g., Staphylococcus aureus, Streptococcus pneumoniae)
- Pairs (diplococci): e.g., Streptococcus pneumonia, Neisseria species.
- Chains: e.g., Streptococcus pyogenes.
- Grape-like clusters: e.g., Staphylococcus species
- Bacilli: rod-shaped bacteria (e.g., Clostridium, Corynebacterium diphtheriae, )
- Curved or comma-shaped: e.g., Vibrio cholerae
- Club-shaped: e.g., Corynebacterium diphtheriae
- Coccobacilli: intermediate shape between cocci and bacilli (e.g., Haemophilus influenzae)
- Spirochetes: long, slender, spiral-shaped bacteria with several coils (e.g., Treponema pallidum, Borrelia burgdorferi, Leptospira interrogans)
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Staining Reaction:
- Gram-positive bacteria appear violet after the Gram stain procedure. Examples include Staphylococcus, Streptococcus, and Clostridium.
- Gram-negative bacteria appear red after Gram stain. Examples include Escherichia coli, Klebsiella, Vibrio, and Haemophilus.
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Acid-fast stain: Used to identify bacteria with a waxy cell wall (e.g., Mycobacterium tuberculosis)
Classification According to the Cell Wall
- Lacking cell wall: Mycoplasma
- Flexible cell wall: Spirochetes (e.g., Treponema)
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Rigid cell wall:
- Filamentous: Streptomyces (antibiotic producers)
- Simple Unicellular: Obligate intracellular bacteria (e.g., Rickettsia, Chlamydia)
- Free-living bacteria: Other bacteria that are free-living in nature.
Medically Important Bacteria
- Diagrams illustrate the relationships between different bacterial types based on cell wall structure, Gram stain, etc.
Test Your Understanding (Example Questions and Answers)
- Q1: Peptidoglycan is found in Gram-positive bacteria.
- Q2: Treponema pallidum is an example of a spirochete.
- Q3: Staphylococcus aureus is a Gram-positive bacteria.
- Q4: Neisseria species are Gram-negative cocci.
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