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Questions and Answers
Which of these organisms is NOT classified as a microorganism?
Which of these organisms is NOT classified as a microorganism?
Bacteria do not cause human disease.
Bacteria do not cause human disease.
False
What is the primary reason bacteria must be stained to be visible under a light microscope?
What is the primary reason bacteria must be stained to be visible under a light microscope?
Their small size and relative transparency.
The classification of bacteria by shape and structure is known as _____
The classification of bacteria by shape and structure is known as _____
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Which of the following is an example of a gram stain?
Which of the following is an example of a gram stain?
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Name one bacterium that causes syphilis.
Name one bacterium that causes syphilis.
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What is the shape of Bacilli?
What is the shape of Bacilli?
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Match the following bacteria with the diseases they cause:
Match the following bacteria with the diseases they cause:
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Which characteristic is NOT used in the classification of bacteria?
Which characteristic is NOT used in the classification of bacteria?
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Viruses can replicate without the assistance of a host cell.
Viruses can replicate without the assistance of a host cell.
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Study Notes
Microbiology
- The study of different organisms including:
- Archaea
- Bacteria
- Protozoa
- Algae
- Fungi
- Acellular entities
Domains of Living Organisms
-
Eukarya: Includes all members of the living world except prokaryotes. This domain comprises algae, fungi, and protozoa.
-
Bacteria:
- Unicellular organisms, generally smaller than eukaryotic organisms.
- Diverse in cell shape, motility, metabolism, and oxygen requirements.
- Most bacteria are not harmful to humans, but many diseases are caused by bacteria.
-
Archaea:
- Similar in shape, size, and appearance to bacteria.
- Biochemically distinct from bacteria.
- Thrive in extreme environments characterized by high heat, cold, pH, or salt concentration.
Medically Significant Entities
-
Viruses:
- Lack many characteristics of living cells.
- Unable to replicate independently and require host cell biosynthetic processes.
-
Prions:
- Infectious agents composed solely of proteins.
Domain Bacteria
- Organisms are grouped and named based on:
- Morphologic characteristics
- Biochemical characteristics
- The binomial Linnaean system is used for naming bacteria with genus and species:
- Staphylococcus aureus
- Escherichia coli O157:H7
Morphology
-
Study of bacteria's shape and structure.
-
Colony morphology: Based on the size, color, shape, and texture of colonies grown on an agar plate.
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Microscopic morphology: Examines bacteria based on cell size, shape, and arrangement.
Colony Characteristics
-
Size: Colonies vary from pinpoint (less than 1 mm) to as large as 5-10 mm in diameter.
- Only well-separated colonies should be measured as crowding can affect size.
-
Margin: The periphery of the colonies can exhibit different characteristics:
- Entire: Rounded projections
- Notched
- Threadlike
- Filamentous
- Serrated
- Lobate
-
Surface texture: The surface can be:
- Smooth: Shiny, glistening
- Rough: Dull, granular
- Mucoid: Slimmy or gummy
- Wrinkled
- Concentric
- Contoured
- The surface texture can indicate virulence.
-
Elevation:
- Flat
- Raised
- Convex
-
Consistency: Determined by touching the colony with a transfer needle
- Butyrous: Butterlike
- Viscous
- Stringy
- Rubbery
- Dry
- Brittle
- Powdery
-
Optical features:
- Transparent
- Translucent
- Opaque
-
Pigmentation: Some bacterial species produce pigmented colonies.
- Examples:
- Serratia marcescens: Red
- Staphylococcus aureus: Gold
- Micrococcus luteus: Yellow
- Bacteroides melaninogenicus: Black
- Pseudomonas aeruginosa: Blue green
- Examples:
Bacterial Shape and Arrangement
-
Cocci: Spherical cells
- Chains: Streptococcus species
- Pairs/Diplococci: Neisseria gonorrhea
- Clusters: Staphylococcus species
-
Bacilli: Cylindrical and rod-shaped organisms
- Pseudomonads
- Escherichia
-
Coccobacilli: Short, rounded rods
- Haemophilus
-
Spirochetes and Spirilla: Helical, corkscrew-shaped organisms
- Treponema pallidum
-
Vibrios: Comma-shaped rods
- Vibrio cholerae
-
Pleomorphic organisms: Exist in varied forms
- Legionella
- Corynebacterium
Examples of Medically Important Bacteria
- BACTERIA | DISEASE |
- Treponema pallidum | Syphilis|
- Neisseria gonorrhea | Gonorrhea|
- Salmonella typhosa | Typhoid fever |
- Vibrio cholerae | Cholera |
- Yersinia pestis | Bubonic plague |
- Staphylococcus aureus | Boils |
- Clostridium tetani | Tetanus |
- Clostridium botulinum | Botulism |
- Legionella pneumophila | Legionnaire's disease |
Stains
- Bacteria are stained to improve visibility under a light microscope due to their small size and transparency.
- Staining characteristics are helpful in classification.
- Main types of staining reactions:
- Simple stain
- Gram stain
- Acid-fast stain
- Endospore stain
- Capsule stain
Simple Stain
- Single stain is used to color the cells.
- Examples:
- Methylene blue
- Basic fuchsin
- Crystal violet
- Safranin
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Description
Test your knowledge on various microorganisms including archaea, bacteria, protozoa, algae, fungi, and acellular entities. Explore the characteristics and significance of each domain of living organisms. Understand the role of medically significant entities like viruses and prions.
