58 Questions
What is the main characteristic that distinguishes prokaryotes from eukaryotes?
Presence of a nucleus
Who is credited with the discovery of the largest bacterium?
Sergei Winogradsky
Which type of microbe requires a microscope to be seen?
Protozoa
What is the significance of metagenomes in understanding microbial populations?
They capture the genetic diversity of entire microbial communities
What was Lynn Margulis's proposed mechanism for the evolution of eukaryotic organelles?
Endosymbiosis
What did Carl Woese's analysis of DNA from prokaryotes living in hot springs reveal?
They were a distinct form of life
What did microbiologists do to define microbial species despite the difficulty in defining them?
Devised working definitions of microbial species
How did Woese's discovery impact the classification scheme of five kingdoms?
It replaced the five kingdoms with three equally distinct groups called domains
What substance did Alexander Fleming discover that kills bacteria?
Penicillium mold
What is the main purpose of immunization?
To stimulate an immune response by inoculation with an attenuated pathogen
What did Sergei Winogradsky and others demonstrate about the importance of bacteria?
Bacteria play a crucial role in geochemical cycling
What are endosymbionts?
Microbes that live inside a larger host organism
What is resolution in the context of observing microbes?
The smallest distance by which two objects can be separated and still be distinguished
What does detection refer to in the context of observing microbes?
The ability to determine the presence of an object
What does magnification mean in the context of observing microbes?
An increase in the apparent size of an image to resolve smaller separations between objects
Which type of microscopy is described as the simplest?
Light microscopy
What is the main difference between a simple stain and a differential stain?
A simple stain adds dark color specifically to cells, but not to the external medium or surrounding tissue, while a differential stain stains types of cell differently to distinguish them
Which type of bacteria retains the crystal violet stain in the Gram stain?
Gram-positive bacteria
What is the main use of fluorescence microscopy in microbiology?
To label specific cells even in environmental samples
What do molecules with fluorescence properties (fluorophores) do in fluorescence microscopy?
They absorb light of lower energy and then emit light of higher energy
What is the size range of prokaryotes?
0.4–10 µm
Which shapes of bacteria are common to many taxonomic groups?
Bacilli: rods, Cocci: spheres
What must exist for electromagnetic radiation to resolve an object?
Contrast between object and its medium, Wavelength smaller than the object, Enough light intensity
What is the wavelength range of visible light?
~400–750 nm
What type of interaction occurs when the wavefront bounces off the surface of an object?
Reflection
In bright-field microscopy, what is used to increase resolution?
Shorter-wavelength light
What is the total magnification when the ocular lens has a magnification of 5X and the objective lens has a magnification of 20X?
100X
How does fixation enhance the detection and resolution of cells under a microscope?
By making cells adhere to a slide in a fixed position
What is the size range of prokaryotes?
0.4–10 µm
What are the common shapes of bacteria found in many taxonomic groups?
Rods and spheres
What is the wavelength range of visible light?
~400–750 nm
What conditions must exist for electromagnetic radiation to resolve an object?
Contrast between object and its medium, wavelength smaller than the object, and others
What is part of the spectrum of electromagnetic radiation?
Light
What is a subcellular structure that is too small to resolve by light microscopy?
Subcellular structures are too small to resolve by light microscopy
What is the main characteristic that distinguishes prokaryotes from eukaryotes?
Lack of a true nucleus and other membrane-bound organelles
What is the main purpose of a simple stain?
To add dark color specifically to cells
What distinguishes a differential stain from a simple stain?
A differential stain stains types of cell differently to distinguish them
Which type of bacteria retains the crystal violet stain in the Gram stain?
Gram-positive bacteria
What does fluorescence microscopy allow scientists to do?
Label specific cells even in environmental samples
What happens when a specimen absorbs light of a defined wavelength and then emits light of lower energy?
It fluoresces
What is the most famous differential stain mentioned in the text?
Gram stain
What is the main characteristic of a differential stain?
It stains types of cell differently to distinguish them
Which type of bacteria do not retain the crystal violet stain in the Gram stain?
Gram-negative bacteria
What can fluorescence microscopy be used for in live organisms?
To observe fluorescence.
What is the definition of resolution in the context of observing microbes?
The smallest distance by which two objects can be separated and still be distinguished
What is the main difference between light microscopy and other types of microscopy?
Light microscopy is the simplest, while other types are more complex
What does detection refer to in the context of observing microbes?
The ability to determine the presence of an object
Which organisms fall within the size range that structures can be seen under a light microscope?
Protozoa, algae, fungi
What is the definition of magnification in the context of observing microbes?
The increase in the apparent size of an image to resolve smaller separations between objects
What is the significance of powerful microscopes in observing microbes?
They enable detection of microbes in familiar and unexpected habitats
What is meant by the term 'microbes differ in size, over a range of a few orders of magnitude'?
Microbes have a wide range of sizes spanning several orders of magnitude
What is the definition of absorption in the context of light interacting with an object?
The acquisition of the photon’s energy by the absorbing object
In bright-field microscopy, what technique is used to increase resolution?
Use shorter-wavelength light
What is the main purpose of fixation in microscopy?
To enhance detection and resolution of cells
What does refraction refer to in the context of magnification by a lens?
The bending of light as it enters a substance that slows its speed
How does total magnification in a compound microscope relate to the ocular and objective lenses?
Total magnification is the product of the magnification of the ocular and objective lenses
What occurs when the wavefront interacts with an object smaller than the wavelength of light?
Scattering
What is the main function of glass with curvature (lens) in magnification?
To bend light rays to intersect at a focal point
Learn about the profound impact of microbes and scientists on human history, explore evidence of microbial life dating back billions of years, and understand the categorization of all life forms on the phylogenetic tree of life.
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