51 Questions
What did Chapter 1 compare and contrast?
Prokaryotes with eukaryotes
Who discovered microorganisms?
Antony van Leeuwenhoek
What was of foremost importance in the development of microbiology?
Quality microscopes
What did microbiology become only after the development of appropriate instruments and techniques?
A scientific discipline
What kind of image does a compound light microscope form in the ocular diaphragm?
Real image
What is used to increase resolution in a compound light microscope?
Short-wavelength light
What is the purpose of immersion oils of high refractive index in a compound light microscope?
Increase resolution
What is the theoretical maximum resolving power for a compound light microscope?
0.2 µm
What kind of aberrations did early compound microscopes suffer from?
Chromatic and spherical aberrations
What are prokaryotic cells almost invisible when viewed with?
Ordinary compound light microscope
What are microorganisms often stained with to increase contrast between the cells and their environment?
Aniline dyes
Who perfected the compound light microscope in the late 19th century?
Ernst Abbe
What are most dyes used to stain microorganisms?
Aniline dyes
What allows for increased resolution in the compound light microscope?
Improved lenses
What kind of microscopes are used for observing internal cell structures?
Modified compound microscopes
What is used to correct lens aberrations in compound microscopes?
Multicomponent lens systems
What is the typical near point of the human eye for adults?
250 mm
What type of microorganisms have a cell diameter of only 0.001 mm?
Prokaryotes
Who is credited with constructing simple microscopes that could magnify 200-300-fold?
Antoni van Leeuwenhoek
What type of microscopes use two lenses (objective and eyepiece) to magnify specimens?
Compound microscopes
What is the overall magnification when using a 60× objective lens and a 10× eyepiece?
600×
What is used to provide high-intensity light and control brightness in compound microscopes?
Condenser lens and iris diaphragm
What is the useful magnification maximum of a light microscope?
1,000× to 2,000×
What does the resolving power of an optical system define?
The distance between two closely spaced points in an object that can be separated by the lens in the formation of an image
What does the resolving power equation include?
Wavelength of light, refractive index, and angular aperture
What does a lower value of resolving power indicate about the optical system?
Higher ability to produce a detailed image
What does improving image formation in light microscopy involve?
Understanding and optimizing the resolving power of the optical system
Which type of stain is useful in staining positively charged cell components such as protein?
Acid dyes
What type of microscopy produces a bright image against a dark background, allowing the observation of living cells?
Darkfield microscopy
Which microscopy technique amplifies the slight difference in refractive index between microbial cells and their aqueous environment to enhance contrast?
Phase contrast microscopy
Which type of bacteria retain the color of a dye when rinsed in a solution of ethanol containing hydrochloric acid?
Acid-fast bacteria
Which type of stain is used to distinguish between gram-positive and gram-negative bacteria?
Gram stain
What type of microscopy is advantageous for specifically staining nucleic acid components of cells?
Fluorescence microscopy
What is the main purpose of simple stains in microscopy?
To add color to the entire microorganism for better visibility
Which type of microscopy allows the observation of cells on opaque surfaces?
Fluorescence microscopy
What is the primary characteristic of basic dyes used for staining microorganisms?
Positively charged chromophore
What is the distinguishing feature of acid-fast bacteria?
They retain the color of a dye when rinsed in ethanol containing hydrochloric acid
Which type of stain is effective for staining microorganisms with a near-neutral internal pH and negatively charged cell surface?
Basic dyes
What is the main advantage of wet-mount preparations in darkfield microscopy?
Ability to observe living cells in their normal growth environment
Which microscopy technique uses a laser beam to illuminate and view microorganisms in three-dimensional space?
Confocal scanning microscopy
What is the illuminating source used in transmission electron microscopy (TEM)?
Electrons
Why is TEM not suitable for observing living cells?
It requires a vacuum chamber
What is used to focus the electron beam in transmission electron microscopy?
Magnetic fields
What is the major application of TEM in biology?
Observing internal cell structures
What type of light is used for incident illumination in fluorescence microscopes?
Ultraviolet light
What type of light is emitted by fluorescent dyes in fluorescence microscopes?
Long-wavelength light
What is the theoretical resolution achieved by transmission electron microscopy (TEM)?
2 Å
What is used to replace optical lenses in TEM?
Magnetic fields
What is the purpose of heavy metal stains like phosphotungstic acid or uranyl acetate in TEM?
To provide color contrast
What type of images do electron micrographs in TEM provide compared to light microscopes?
Increased detail
What is the illuminating source used in epifluorescence scanning microscopy?
Laser beam
Study Notes
Microscopy Techniques in Microbiology
- Fluorescence microscopes use short-wavelength light from mercury or halogen lamps for incident illumination and view longer-wavelength light emitted by fluorescent dyes.
- Confocal scanning microscopes use a laser beam to illuminate and view microorganisms in three-dimensional space, providing images free from diffracted light.
- Epifluorescence scanning microscopy uses a laser beam to illuminate and view a cross-section of the specimen stained with a fluorescent dye.
- The transmission electron microscope (TEM) utilizes electrons as the illuminating source, achieving a theoretical resolution of about 2 Å, twice the diameter of a hydrogen atom.
- TEM uses electromagnetic lenses to focus the electron beam and requires a vacuum to permit the flow of electrons through the lens system.
- The real image in TEM is formed by electrons bombarding a phosphorescent screen, and the photograph is taken by a camera mounted below the screen.
- TEM is not suitable for observing living cells due to the vacuum chamber requirement and uses thin sectioning to observe internal cell structures.
- Electron micrographs in TEM provide increased detail compared to light microscopes, even at similar magnifications.
- Cell preparations for TEM are placed on a small grid and stained with heavy metal stains like phosphotungstic acid or uranyl acetate.
- The major application of TEM in biology is to observe internal cell structures, requiring a more elaborate procedure called thin sectioning.
- TEM has a larger size than the ordinary light microscope due to the vacuum chamber and use of electron magnets for lenses.
- Unlike light microscopes, TEM images are formed using electrons as the illuminating source and magnets to replace optical lenses.
Test your knowledge of microscopy techniques in microbiology with this quiz. Explore fluorescence microscopy, confocal scanning microscopy, and transmission electron microscopy (TEM), including their principles, applications, and differences from light microscopes.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
