Lecture 2 Flashcards
microscopes, why we study microbes & survey of microbes
1
Q
Define “resolution.”
A
- the ability to see two items as separate and distinct
- microscopes tend to have a limit on resolution, whereas magnification can, in theory, be increased without limit
- the resolution limit of the light microscope would be the wavelength of light because light has to be able to fit between two objects to differentiate them from each other
1
Q
Define “magnification.”
A
- the use of a lens to enlarge an object
- as magnification increases, we are enlarging an object and looking at it more closely
2
Q
Define “contrast.”
A
- the ability to see something as different from its surroundings
- it depends upon differences in the amount of light transmitted by the object compared to its surroundings
- to view a specimen properly, a proper balance between magnification, resolution and contrast must be achieved
3
Q
Three types of microscopy
A
1) light (including bright-field, phase-contrast, dark-field, and fluorescence)
2) confocal
3) electron
4
Q
Light microscope (compound)
A
- illuminator is the light source
- light passes through a condenser which directs light rays through the specimen
- light rays will then pass through the objective lens
- the image is magnified by the ocular lens
5
Q
Kohler illumination
A
- a series of steps done at a specific point to achieve an even illumination of a specimen which increases contrast
6
Q
Immersion oil
A
- oil has the same refractive index as glass, and when used, fills up the space between the lens and slide to maximize resolution
- for oil immersion lens, 100x
7
Q
Staining
A
- different types of stains maintain high resolution and increase contrast
- sometimes used to isolated parts of microbes or detect certain types of microbes
8
Q
Gram Stain
A
- one of the first classifications done with a bacterium
- G+ versus G- different cell wall structures
9
Q
What kind of cells are ideal for bright-field microscopy?
A
- large and pigmented cells
10
Q
Phase-contrast
A
- based on small differences in the refractive index between the specimen and the background
- the small differences are amplified by a phase ring leading to a dark image on a light background
- useful for live specimens
11
Q
Dark-field
A
- light reaches the specimen from the side only, allowing for an image that is light on a dark background
- useful for live specimens
12
Q
What kind of microscopy should be used to increase contrast for dead cells?
A
Fluorescence microscopy
13
Q
Confocal microscopy
A
- specimens are stained with fluorochrome dyes and then only small portions of the field are illuminated with light at a time rather than the whole field of view
- short wavelength (blue) light is used to improve resolution
- the light illuminates each plane in a specimen to produce 3D images up to 100 um deep
- images are made pixel by pixel and put together using a computer
14
Q
Electron microscopes
A
- very high resolution
- a beam of electrons (smaller wavelength)
- two types: scanning and transmission
15
Q
Transmission Electron Microscopy
A
- a beam of electrons passes through a specimen, then an electromagnetic lens, to a screen or film
- the more dense the material is in a sample, the more electrons pass through
16
Q
Scanning Electron Microscopy (SEM)
A
- 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
17
Q
What is “microbiology”?
A
- the study of living things that are too small to be seen without magnification
- these tiny living things are called microbes or microorganisms
18
Q
Where are microbes found?
A
- they are found everywhere!
- marine and freshwater soils, hydrothermal vents, air ice, etc.
- microbes are the most abundant organisms on Earth and make up most of the living mass of Earth
19
Q
How did microbes make life on Earth possible?
A
- microbes were the first forms of life
- life on Earth may have emerged from the bottom of the oceans (hydrothermal water)
- microbes were the only life forms for most of the history of Earth
20
Q
Impact of microbes as agents of disease
A
- 1% are pathogenic
- technology and further understanding of these microbes have decreased the effects of many infectious diseases
21
Q
Impact of microbes in agriculture and human nutrition
A
- microbes recycle nutrients
- nitrogen fixation
- ruminant animals (e.g. cow, sheep, bunny)
we rely on microbes in our digestive system to produce certain vitamins
22
Q
Impact of microbes in food and industry
A
- food safety and spoilage
- fermented foods
- production if antibiotics and chemicals, and insulin
23
Q
How many domains is life organized into?
A
- 3
- bacteria, archae, eukarya
24
Describe domain Bacteria:
1) prokaryotic or eukaryotic?
2) do they have cell walls?
3) if yes, what are they made of?
4) are they capable of photosynthesis?
5) how do they reproduce?
- prokaryote (no membrane-bound organelles)
- have cell walls made of peptidoglycan
- some (cyanobacteria) uses organic and/or inorganic molecules, or photosynthesis for energy
- reproduces through binary fission
25
Describe domain Archaea:
1) prokaryotic or eukaryotic?
2) do they have cell walls?
3) if yes, what are they made of?
4) are they capable of photosynthesis?
5) how do they reproduce?
6) where can they be found?
- prokaryotic
- cell wall: either none, or composed of pseudomeurin or S-layer
- no, but uses inorganic molecules for energy
- reproduce through binary fission, fragmentation, or budding
- can be found in extreme environments (methongens, halophiles, thermophiles)
26
Describe Protists:
1) prokaryotic or eukaryotic?
2) do they have cell walls?
3) if yes, what are they made of?
4) are they capable of photosynthesis?
5) how do they move around?
6) how do they reproduce?
- unicellular eukaryotes
- some have cell walls made of large variety
- absorb or ingest molecules from their environment
- some can photosynthesize, others are parasties
- can move through the use of pseudopods, flagella or cilia
- can reproduce sexually or asexually
27
Describe Fungi:
1) prokaryotic or eukaryotic?
2) do they have cell walls?
3) if yes, what are they made of?
4) are they capable of photosynthesis?
5) how do they reproduce?
- eukaryote
- cell walls contain chitin
- uses organic molecules for energy absorption
- cannot do photosynthesis
- cell walls contain chitin
- can reproduce asexually or sexually
28
Describe Archaeplastida (Algae):
1) prokaryotic or eukaryotic?
2) do they have cell walls? (yes, no, some)
3) if yes, what are they made of?
4) are they capable of photosynthesis?
5) how do they move around?
6) how do they reproduce?
- eukaryotes
- some, cellulose
- uses photosynthesis for energy
- not plants
- some can move via flagella
- can reproduce sexually or asexually
- unicellular or multicellular
29
Describe Multicellular Animal Parasites:
1) prokaryotic or eukaryotic?
2) how does their reproductive system compare to their digestive and nervous systems?
3) can they do photosynthesis?
4) what are their life cycles like?
5) list some examples
- eukaryotic
- their reproductive systems are way more enhanced than their digestive and nervous systems
- incapable of doing photosynthesis
- life cycles involve multiple hosts, sexual, and asexual stages
- examples include Platyhelminths and Nematodes
30
Describe Viruses:
1) are they in the three domains of life?
2) describe the structure
3) can they do photosynthesis?
4) how do viruses reproduce?
- not included in the three domains of life but are the most abundant and diverse biological entities on Earth
- small, acellular, consists of a protein and/or lipid membrane surrounding a DNA or RNA core
- no metabolism
- viruses replicate when living in a host cell
31
What are microbes?
1) single-celled microscopic organisms: some can be multicellular, some are colonial (3 types: Bacteria, Archaea, Eukarya)
2) viruses: microscopic but not cellular, and not physiologically active
