Microbiology Final Exam – Complete
Study Guide & Practice Review
Leeuwenhoek
Invented the microscope
Pasteur
- Demonstrated that microorganisms are present in the air
- S-shaped flask
- Showed that microbes are responsible for fermentation
- Pasteurization: high heat for a short time
Koch
Proved that a bacterium causes anthrax and provided the experimental steps- Koch's postulates
Koch's postulates
1. The microorganism must be found in abundance in all organisms suffering from the disease, but
should not be found in healthy organisms
2. The microorganism must be isolated from a diseased organism and grown in a pure culture
3. The cultured microorganism should cause disease when introduced into a healthy organism
4. The microorganism must be re-isolated from the inoculated, diseased experimental host and
identified as being identical to the original specific causative agent
Fleming
Discovered the first antibiotic- penicillin
Brightfield light microscopy
Dark objects are visible against a bright background
Darkfield microscopy
Light objects are visible against a dark background
Transmission electron microscopy
,- Light passes through a ultra-thin section of a specimen, then an electromagnetic lens, to a screen or
film
- Specimen may be stained with heavy metal salts
Scanning electron microscopy
- An electron gun produces a beam of electrons that scans the surface of a whole specimen
- Secondary electrons emitted from the specimen produce the image
Gram stain
A staining method that distinguishes between two different kinds of bacterial cell walls.
Gram stain process
Primary stain: Crystal violet
Mordant: Iodine
Decolorizing agent: Alcohol-acetone
Counterstain: Safranin
Color after gram stain (gram+ vs. gram-)
Gram+: Purple
Gram-: Red
Gram+ cell wall
- One plasma membrane
- Cell wall is thicker so there is more peptidoglycan (made up of alternating NAG & NAM) and
teichoic/lipoteichoic acid (hold cell wall together)
Gram- cell wall
- Two plasma membrane
- Cell wall is thinner so less peptidoglycan and teichoic/lipoteichoic acids
- LPS is the endotoxin in the outer membrane
Endospore stain
A differential stain is used to detect the presence and location of spores in bacterial cells.
Endospore staining process
Primary stain: Malachite green w/ heat
Decolorizing agent: Water
Counterstain: Safranin
Capsule stain
, - Cells stained (positive/basic stain)
- Background stained negative stain)
- Area between stains is the capsule
Acid-fast stain
- The stained waxy walls of the bacteria aren't decolorized by acid-alcohol
- Mycobacterium and Nocardia
Acid-fast stain process
Primary stain: Carbol fuchsin
Decolorizing agent: Acid-alcohol
Counterstain: Methylene blue
Color after acid-fast stain
Acid-fast bacteria: red
Non-acid-fast bacteria: blue
Bacterial shape: Bacillus
Rod-shaped
Bacterial shape: Coccus
Spherical
Bacterial shape: Spirillum/spirochete
Spiral
Bacterial appearance: Diplo-
Pair
Bacterial appearance: Strepto-
Chains
Bacterial appearance: Staphylo-
Clusters
Hypotonic environment
More solutes inside the cell so water rushes in
Hypertonic environment
More solutes outside the cell so water rushes out
Isotonic environment
Solutes are balanced inside and outside the cell so water movement is equal
Study Guide & Practice Review
Leeuwenhoek
Invented the microscope
Pasteur
- Demonstrated that microorganisms are present in the air
- S-shaped flask
- Showed that microbes are responsible for fermentation
- Pasteurization: high heat for a short time
Koch
Proved that a bacterium causes anthrax and provided the experimental steps- Koch's postulates
Koch's postulates
1. The microorganism must be found in abundance in all organisms suffering from the disease, but
should not be found in healthy organisms
2. The microorganism must be isolated from a diseased organism and grown in a pure culture
3. The cultured microorganism should cause disease when introduced into a healthy organism
4. The microorganism must be re-isolated from the inoculated, diseased experimental host and
identified as being identical to the original specific causative agent
Fleming
Discovered the first antibiotic- penicillin
Brightfield light microscopy
Dark objects are visible against a bright background
Darkfield microscopy
Light objects are visible against a dark background
Transmission electron microscopy
,- Light passes through a ultra-thin section of a specimen, then an electromagnetic lens, to a screen or
film
- Specimen may be stained with heavy metal salts
Scanning electron microscopy
- An electron gun produces a beam of electrons that scans the surface of a whole specimen
- Secondary electrons emitted from the specimen produce the image
Gram stain
A staining method that distinguishes between two different kinds of bacterial cell walls.
Gram stain process
Primary stain: Crystal violet
Mordant: Iodine
Decolorizing agent: Alcohol-acetone
Counterstain: Safranin
Color after gram stain (gram+ vs. gram-)
Gram+: Purple
Gram-: Red
Gram+ cell wall
- One plasma membrane
- Cell wall is thicker so there is more peptidoglycan (made up of alternating NAG & NAM) and
teichoic/lipoteichoic acid (hold cell wall together)
Gram- cell wall
- Two plasma membrane
- Cell wall is thinner so less peptidoglycan and teichoic/lipoteichoic acids
- LPS is the endotoxin in the outer membrane
Endospore stain
A differential stain is used to detect the presence and location of spores in bacterial cells.
Endospore staining process
Primary stain: Malachite green w/ heat
Decolorizing agent: Water
Counterstain: Safranin
Capsule stain
, - Cells stained (positive/basic stain)
- Background stained negative stain)
- Area between stains is the capsule
Acid-fast stain
- The stained waxy walls of the bacteria aren't decolorized by acid-alcohol
- Mycobacterium and Nocardia
Acid-fast stain process
Primary stain: Carbol fuchsin
Decolorizing agent: Acid-alcohol
Counterstain: Methylene blue
Color after acid-fast stain
Acid-fast bacteria: red
Non-acid-fast bacteria: blue
Bacterial shape: Bacillus
Rod-shaped
Bacterial shape: Coccus
Spherical
Bacterial shape: Spirillum/spirochete
Spiral
Bacterial appearance: Diplo-
Pair
Bacterial appearance: Strepto-
Chains
Bacterial appearance: Staphylo-
Clusters
Hypotonic environment
More solutes inside the cell so water rushes in
Hypertonic environment
More solutes outside the cell so water rushes out
Isotonic environment
Solutes are balanced inside and outside the cell so water movement is equal
