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Microbiology 211 Exam 2 2025 EDITION SCORE A+
Stains consist of 2 parts:
- Chromophore
- Auxochrome Chromophore Colored portion Auxochrome Charged portion Satins are classified based on ____________ charge. Auxochrome Microorganisms are ___________ charged. Negatively Acidic ( - Charged) stains do _______ bind to microorganism. They bind to the __________ instead. NOT Slide
When staining with acidic ( - Charged) stains: Slide Background: Microorganisms: Colored Colorless The process of staining with acidic stains is referred to as _________ __________. Negative Staining Microorganisms are ________ charged. Negatively Basic ( + Charged) stains only bind to _______________. Do ________ bind to slide. Microorganisms NOT When staining with basic ( + Charged) stains: Slide Background:
- Gram Staining
- Acid-Fast staining
- Capsule Staining
- Endospore Staining Bacterial cell walls fall into one of two categories:
- Gram positive bacteria
- Gram negative bacteria Gram stain is used to differentiate gram __________ and gram ___________ bacteria. Positive Negative Gram Stain-First step preformed: Medical/lab techs: Microbiologists:
- Identifying disease causing bacteria
- Classifying bacteria Gram Positive cell walls:
- Thick Peptidoglycan
- Single Inner Membrane
- Teichoic Acids
- Lipoteichoic Acids
- Purple Stain Gram Negative Cell Walls:
- Outer Membrane
- Thin Peptidoglycan
- Inner Membrane
- Lipopolysaccharide
- Porins
- Periplasmic Space
- Stain Red/Pink Gram Stain:
- Crystal Violet: Primary Stain - 1 Min
- Iodine: Mordant - 1 Min
- Acetone/Ethanol Mixture: Decolorizer - 10 - 30 Min
- Safranin: Secondary Stain - 1 Min Gram Stain:
Acid Fast Stain:
- Carbolfushin (Primary Stain) + Steam (mordant) - 5 Min
- Acid Alcohol (Decolorizer) 2-3 droppers; rise.
- Methylene Blue (Secondary Stain) - 1 Min Acid Fast Stain
- Acid fast bacteria: Hot Pink
- Non Acid Fast Bacteria: Blue Acid fast bacteria __________ decolorization with acid alcohol. Resist Capsule Differentiates:
- Microorganisms that produce capsules
- Microorganisms that do not produce capsules. Capsule-Unique procedure:
- Involves use of both acidic/basic dyes Overview of capsule stain procedure:
- Add loop of microorganisms to one end of slide.
- Add Congo red (Primary stain) to microorganisms.
- Spread Congo red/microorganisms across slide. Capsule Stain:
- Allow Congo red to air dry
- Flood slide with Maneval's: Secondary stain.
- Allow Maneval's to air dry. Congo Red stain's slide background: Acidic ( - Charged Stain) Maneval solution stains microbial cell: Basic ( + Charged Stain) Capsule appears as _______ ________ around microbial cell. White Oval Capsule stain
Green Non spore forming (vegetative) bacteria stain ________. Red Endospore Stain: Endospores are classified based on location in cells:
- Central (Middle of cell)
- Subterminal (Between middle and end)
- Terminal (At end) Endospore Stain-Survival Structures:
- Formed in response to stress
- Allow bacteria to resist: Drying Heat UV Light Chemicals: Bleaches, Peroxides, Alcohols, and other disinfectants commonly used to kill bacteria.
Phase-Contrast Microscope use visible light to:
- Observe
- Magnify specimens Phase-Contrast Microscope contains ___________ __________. Phase Plate When light waves hit microorganisms/phase plate:
- Get shifted out of phase
- Creates contrast Advantages of phase contrast microscopes:
- Stains not required
- Can be used to view living microbes Not possible to view living microbes with a __________ ___________ microscope. Compound Light
- Staining usually involves heat fixing step
- Heat fixing kills microorganisms
Stains Compound Light, Phase Contrast, and Dark Field Microscope:
- All use visible light for magnification.
- All forms of radiation differ in wavelength. Wavelength: Distance between two corresponding parts of a wave. Shorter wavelengths of light: Provide greater resolutions Resolution:
- Image clarity
- Microscopes ability to distinguish 2 points as separate. Microscopes with resolving power of 0.4 nm:
- Distinguishes objects ≥ 0.4 nm apart.
- Compound light microscope resolving power = 0.2 μM
- Electron microscopes resolving power = 0.0002 μM
Fluorescence Microscope use: UV to magnify specimens. UV: Shorter wavelength than visible light. Fluorescence microscopes > Resolution than:
- Compound Light
- Phase Contrast
- Dark Field microscopes Fluorescent substances: Absorb UV and emit visible light. Endospores allow: Bacteria to survive until favorable conditions return. Glycocalyx is found in:
Confocal microscopes use computers to produce: Clear three-dimensional images Electron microscopes use __________ instead of light. Electrons Wavelengths of electrons are shorter than: Wavelengths of UV light and visible light. Resolution quality - From best to worst:
- Electron Microscopes
- Confocal Microscopes
- Fluorescent Microscopes
- Compound Light, Phase Contrast, Dark Field Transmission Electron Microscope (TEM):
- Ultrathin sections of specimens
- Electrons Pass
- Specimens stained with heavy-metal salts.
Scanning Electron Microscope (SEM):
- Electron gun produces beam of electrons.
- Pass through magnetic lenses
- Hit surface of specimen: Emits secondary electrons Produces images Image seen on monitor Electrons pass through:
- Through specimens
- Objective lens
- Projector lens
- Onto screen or film Electron Microscope Benefits:
- Magnify up to 100,000 x.
- Resolving power 0.2 nm. Electron Microscope Drawbacks:
- Costly
- Large/bulky size
- Time consuming
Most do, Very few don't Archaea: Prokaryote or Eukaryote? Cell Wall? Prokaryotic Yes Fungi: Prokaryote or Eukaryote? Cell Wall? Eukaryotic Yes Algae: Prokaryote or Eukaryote? Cell Wall? Eukaryote Yes Protozoa:
Prokaryote or Eukaryote? Cell Wall? Eukaryote Some do, some don't. Animals: Prokaryote or Eukaryote? Cell Wall? Eukaryote No Glycocalyx found in:
- Bacteria
- Eukaryotes that lack cell walls. Glycocalyx Composed of:
- Polysaccharide
- Protein
- Combination of the two Glycocalyx
