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micro exam 1 Flashcards

1
Q

What are the 5 types of microbes?

A
  1. Viruses
  2. Protistans (protozoa and algae)
  3. Fungi
  4. Helminths
  5. Bacteria
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2
Q

How does the concept of spontaneous generation factor into the history o fthe field of microbiology?

A

Spontaneous generation was heavily debated up until the 19th century. Scientists performed various experiments trying to prove whether or not spontaneous generation is true. While these scientists were trying to implement aseptic technique, this was the starting point for aseptic technique as the scientists were trying to make sure their work was being contaminated with outside microorganisms.

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3
Q

What did Redi do in terms of helping disprove spontaneous generation?

A

(1665) He put meat into different containers. One container was sealed and the other was not. Maggots appeared on the meat in the unsealed container, but not in the sealed container.

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4
Q

What did Needham do in terms of helping disprove spontaneous generation?

A

(1745?) He boiled broth and then placed it into two different flasks. One flask he left uncovered and the other flask he covered. Microbes ended up growing in both flasks, most likely because he didn’t boil the water enough or he didn’t sterilize the flasks.

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5
Q

What did Spallanzani do in terms of helping to disprove spontaneous generation?

A

(1775) He put broth into flasks and then boiled them. He left one flask uncovered and covered the other flask. Microbial growth occurred in the uncovered flask, but not the covered flask.

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6
Q

What did Pasteur do in terms of helping disprove spontaneous generation?

A

(1860) Pasteur created curved long-necked flasks and boiled broth in them. Microbes were unable to get into the broth because airborne microorganisms would get stuck in the twists and turns of the flask. This experiment disproved spontaneous generation once and for all.

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7
Q

What are the two sets of techniques that are required to study microbiology? Why are they required

A

Microscopy to visualize microbes

Aseptic technique to manipulate and isolate the microbe that you are studying

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8
Q

What shape is a bacillus?

A

Rod

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9
Q

What shape is a Coccus?

A

sphere

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10
Q

What shape is a spirillum?

A

spiral

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11
Q

What shape is a vibrio?

A

curved rod

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12
Q

what shape is a coccobacillus?

A

short rod

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13
Q

what shape is a spirochete

A

Long, loose helical spiral (similar to a corkscrew)

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14
Q

What are the three most commone bacterial morphologies?

A

Bacillus, coccus, spirillum

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15
Q

Who were the Janssens?

A

(1590) some scholars argue that the Janssens might have invented the compound microscope

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16
Q

Who was Leeuwenhoek?

A

(1775) Credited with the discovering of microorganisms. He called them “wee animalcules”

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17
Q

Who was hooke?

A

(1665) Coined the term “cell”

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18
Q

Explain how virion structure relates to a) host range for phages and animal viruses and b) tissue tropism for animal viruses.

A

A virion’s structure determines what hosts the virion will be able to bind to/enter. For tissue tropism, the virion’s structure will also determine what tissues within an animal’s body the virion will be able to enter.

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19
Q

Consider temperate and virulent phages. Which “lifestyle” is more advantageous in an evolutionary sense and why?

A

Temperate phage lifestyle is more advantageous in an evolutionary sense because they can live inactive within the host cell while the host cell reproduces and passes on the phage’s DNA to its daughter cells. Furthermore temperate phages can undergo the lytic cycle as well when needed.

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20
Q

What are Virulent phages and what cycle do they undergo?

A

T2 phages; lytic cycle

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21
Q

What are temperate phages and what cycle do they undergo?

A

Lambda phage; lysogenic cycle, but can go lytic when needed

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22
Q

What are the 5 basic steps of viral replication?

A
  1. Attachment
  2. Entry
  3. Biosynthesis
  4. Assembly
  5. exit/release
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23
Q

Why do viral capsids, both helical and icosahedral, possess geometrically regular symmetry?

A

Whatever angle the viroid approaches the cell, they will be able to attach to the host

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24
Q

How does the lytic cycle differ from the lysogenic cycle?

A

In the lytic cycle, when the bacteriophage injects its DNA into the host cell, the host cell’s DNA is destroyed. The bacteriophages. Phage DNA will then replicated and phages will be assembled. The phages are then released through lysis which results in the death of the host cell.

In the lysogenic cycle, when the bacteriophage injects its DNA into the host cell, the phage DNA becomes embedded in the host genome. The host cell will replicate and create daughter cells that carry the phage DNA. When introduced to stressful conditions, then the host cell undergoes the lytic cycle.

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25
Q

What is a bacteriophage?

A

Virus that attacks bacteria

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26
Q

How does a temperate phage “decide” whether to go lytic or lysogenic cycle when it enters a new host cell?

A

When the host cell is under stressful conditions (such as exposure to UV light, lack of nutrients), the cell will undergo the lytic cycle

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27
Q

What is induction in terms of the lytic/lysogenic cycle

A

The process in which under stressful conditions, temperate phage DNA will pop out of the host cell DNA and undergo the lytic cycle

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28
Q

What is transduction in terms of the lytic/lysogenic cycle?

A

When a piece of bacterial DNA/chromosome is transferred by the phage to a new bacterial cell during the lytic/lysogenic cycle

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29
Q

What is lysogenic conversion? Do you know two examples that were noted in our text?

A

A change in phenotype of the host due to genes brought into the genome by a phage.

In both of these bacteria cells, the introduction of a phage makes the bacteria more virulent:
1. In V. cholera, phage encoded toxin can cause severe diarrhea
2. In C. botulinum, the toxin can cause paralysis

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30
Q

Explain why virulent phages follow a one-step “growth” curve

A

Virions that were replicating within the host cell are all released at the same time during lysis

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31
Q

What is the inoculation phase of the virulent growth curve.

A

The first phase - when the inoculum of virus binds to host cells

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32
Q

What is the eclipse phase of the virulent growth curve

A

The second phase - when viruses are penetrating the host cells and no virions are detected in the media

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33
Q

What is the burst phase of the virulent growth curve

A

third phase - when the host cell lysis, releasing many viral particles at once

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34
Q

What is burst size of the virulent growth curve

A

The number of virions released per bacterium

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35
Q

What are the two methods of transmission used by plant viruses to infect host cells? Why must plant viruses employ these tactics?

A
  1. through holes in the cell wall created by insect vectors or by mechanical means
  2. Once the virus is inside the plant cell, it can travel through gap junctions within the plasmodesmata to reach other plant cells

Plant viruses must employ these tactics in order to get through the thick cell wall of the plant

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36
Q

Describe how the release step of the replication cycle makes an animal virus enveloped vs naked.

A

An animal virus buds off of its host rather than lysis (killing off the host). During the budding process, the animal cell obtains a small portion of the phospholipid membrane of the host cell, creating an envelope around the animal virus.

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37
Q

What is a viroid and how does it differ from a virus?

A

Viroids consist only of a short strand of RNA and are capable of self-replication. They often negatively impact plants. Unlike virisuses, viroids do not have a protein coat to protect their genetic information. Like viruses, they take control of the host machinery to replicate their RNA genome.

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38
Q

What is a prion and how does it differ from a virus?

A

Prions are subviral, and do not contain DNA or RNA. They are misfolded proteins, and result in diseases within animals

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39
Q

What is a virusoid and how does it different from a virus

A

subviral particles that are non-self replicating. In order to replicate, they need a “helper-virus.” Like viroids, virusoids also only consist of RNA (no protein) and impact plants.

40
Q

How do sterile technique and aseptic technique differ? Give examples of when each is commonly used.

A

Sterile technique is intended to completely remove any microorganisms. Aseptic technique is intended to minimize contamination from all pathogens.

An example of sterile technique would be a doctor performing any procedure that could introduce microbes to a patient. Aseptic technique would be the techniques we use in lab to ensure we are only looking at the microbes we want to look at.

41
Q

What is a brightfield microscope

A

The type of microscope that we use in class. A compound microscope with two or more lenses that produce a dark image on a bright background

42
Q

What is a darkfield microscope?

A

similar to a brightfield microscope, but a small, opaque disk is placed in between the illuminator and the condenser lens. The only light that reaches the objective lens is light that has been reflected or refracted by structures in the specimen. Resulting image shows bright objects on a dark background.

43
Q

What is a phase-contrast microscope?

A

Uses refraction and interference caused by structures in a specimen to create high-contrast, high-resolution images without staining. To create altered wavelength paths, an annular stop is used in the condenser.

44
Q

What are fluorescence microscopes?

A

Use fluorescent chromophores called fluorochromes, which are capable of absorbing energy from a light source and then emitting this energy as visbil light.

45
Q

What is a transmission electron microscope?

A

Similar to brightfield microscope in the way that it functions, but uses an electron beam to focus the image. Electrons pass through the specimen. Specimen that is looked at needs to be very thin.

46
Q

What is a scanning electron microscope

A

Forms images of surfaces of specimens from electrons that are knocked off of specimens by a beam of electrons.

47
Q

Contrast the function of bacterial endospores with spores made by either plants or fungi.

A

Bacterial endospores are not created with the function of reproduction as plants or fungi endospores are. Instead, bacterial endospores protect the bacterial genome in a dormant state when bacterial conditions are unfavorable. They allow bacterial cells to survive long periods without water, food, or even exposure to chemicals.

48
Q

What is sporulation?

A

The process by which vegetative cells transform into endospores

49
Q

How are endospores formed?

A

When environmental conditions are unfavorable, these steps occur:

  1. DNA replicates
  2. Membranes form around the replicated DNA
  3. The forespore (the replicated DNA) forms additional membranes
  4. Protective cortex forms around the spore
  5. protein coat forms around the cortex
  6. Endospore is released
50
Q

What is germination?

A

When an endospore returns to a vegetative state

51
Q

What are plasmids? How do they contribute to antibiotic resistance?

A

Plasmids are small, circular double-stranded DNA molecules. They often carry genes that consist of advantageous traits. They can contribute to antibiotic resistance when transferred to other bacteria cells

52
Q

What are inclusion bodies?

A

Structure within prokaryotes that have the ability to store excess nutrients within cytoplasmic structures

53
Q

Name three examples of inclusion bodies

A

Magnetosomes: inclusions of magnetic iron oxide or iron sulfide surrounded by a lipid layer. These allow cells to align along a magnetic field, aiding their movement.
Carboxysome: aids in carbon metabolism
Starch granules: lumps of starch that can be used for energy storage

54
Q

Compare and contrast a typical prokaryotic chromosome with a typical eukaryotic chromosome.

A

Eukaryotic cells have multiple rod-shaped chromosomes that are found within the nucleus. Prokaryotic cells generally have a single, circular chromosome located in a nucleoid.

55
Q

Contrast 70S and 80S ribosomes. Explain how they are evidence supporting the Endosymbiont Theory.

A

70s: found with prokaryotic
80s: found within eukaryotic cells

They are evidence because mitochondria and chloroplasts also have 70s ribosomes

56
Q

Do you recall two other pieces of evidence that support the Endosymbiont Theory (probably learned in Cell Bio)?

A
  1. Both mitochondria and chloroplasts are membrane-bounded structures
  2. Both have circular chromosomes
  3. Both are capable of ATP synthase/electron transport chain
57
Q

What are pili and what do bacteria use them for?

A

Pili are LONGER, FEWER numerous protein appendages that aid in attachment to other bacteria that you want to transfer bacteria to. NOT for motility

58
Q

What are fimbriae and what do bacteria use them for?

A

Short, bristle like proteins projecting from the cell. They help the cell attach to surcaces. NOT for motility.

59
Q

Compare and contrast prokaryotic and eukaryotic flagella

A

prokaryotic flagella act as propellers and are attached to a basal hook/body which helps with motility. They are a stiff structure that uses rotary movements.

Eukaryotic flagella are also used for movement but are structurally different. They consist of a flexible whip and back and forth motions.

60
Q

What direction of movement for flagella is “twiddle” or tumbling

A

clockwise

61
Q

What directions of movement for flagella is running?

A

counterclockwise

62
Q

What is a monotrichous flagellar arrangement

A

one flagellum at one end of the cell

63
Q

What is a amphitrichous flagellar arrangement?

A

have a flagellum or tufts of flagella located at both ends of the cell

64
Q

what is a peritrichous flagellar arrangement?

A

flagella all over the perimeter of the cell

65
Q

what is a lophotrichous flagellar arrangement?

A

a tuft of flagella at one end of the cell

66
Q

Describe and explain why the path along which a bacterium moving away from a chemorepellent (or toward a chemoattractant) moves is called a “biased, random walk.

A

Their movement is called a biased random walk because the becterium is twiddling, moves (runs) in a random direction, then stops and evaluates whether they are moving toward something they like or dislike, and adjusts their position accordingly. They then repeat this until they are moved where they want to be.

67
Q

Why are a) Brownian motion and b) twitching motility not forms of true motility?

A

Brownian motion is vibrational action caused by random activity of the water molecules.

Twitching motility occurs when a biofilm has been created and the bacteria have lost their flagella, but the bacteria may contact and extend their pilli which causes them to twitch, but not enough to move even a single body length.

True motility is characterized by the movement of individual cells over several body lengths.

68
Q

What is an axial filament and how does its structure affect bacterial motility?

A

An axial filament is found on a spirochete and is similar to a flagellum, but it wraps around the cell and runs inside the cell body of a spirochete in the periplasmic space between the outer membrane and the plasma membrane.

69
Q

What is peptidoglycan? Describe its structure/function and explain how it is synthesized. Also: why is it important to know that peptidoglycan is one continuous polymer surrounding a bacterial cell?

A

PDG is the major component of bacterial cell walls. PDG is a SINGLE mesh-like structure with no loose ends surrounding the cell. The purpose of PDG is to prevent lysis due to osmotic pressure

70
Q

Compare and contrast the structure and function of Gram negative and Gram positive cell envelopes.

A

Gram +
- Thick layer of PDG
- No outer membrane
- Narrow periplasmic space
- TA is thought to increase rigidity

Gram -
- Think layer of PDG
- Lipopolysaccharides (LPS) as outer layer, which makes the cell hydrophobic and acts as an endotoxin

Both
- Include plasma membrane as innermost layer
- Both include PDG
- Both include PPS

71
Q

What is the periplasmic space and what are its 2 functions?

A

Space between the plasma membrane and the peptidoglycan wall. Functions are:
1. High end of H+ gradient for ATP synthase
2. PDG synth enzymes

72
Q

What is the inorganic and organic terminology used for carbon?

A

Inorganic: Auto
Organic: Hetero

73
Q

What is the inorganic and organic terminology used for energy source?

A

Inorganic: Photo
Organic: Chemo

74
Q

What is the inorganic and organic terminology used for electron source?

A

inorganic: litho
organic: organo

75
Q

What is the difference between general and enriched media?

A

General: Most bacteria can grow on it without added substances ex: TSA and TSB

Enriched: Contains growth factors, vitamins, etc. to promote growth of fastidious organisms (SBA)

76
Q

What is the difference between complex and defined media?

A

Complex: Has a recipe that includes an extract where the exact amount/chemical composition is not known (TSA, TSB, SBA)

Defined: Has a specific recipe (ex: 1% tryptone broth)

77
Q

What is the difference between differential and selective media?

A

Differential: Has an extra ingredient that will show up or indicate how different bacteria respond; makes it easy to distinguish colonies of different bacteria by a change in color (SBA will show hemolysis)
Selective: Has an ingredient that will kill off or reduce/inhibit unwanted microbes (ex: PEA phenylethyl alcohol agar)

78
Q

Explain why extreme thermophiles can withstand – in fact, REQUIRE – very high temperatures for growth.

A

The ratio of saturated to polyunsaturated lipids increases, which limits the fluidity of the cell membrane.

Their DNA sequences show a high proportion of G-C nitrogenous bases, which are held together by three hydrogen bonds as opposed to two.

These changes contribute to the resistance of proteins to denaturation

79
Q

What are thermophiles?

A

Heat-loving microbes; they grow best between 50-80 C

80
Q

What are mesophiles?

A

“Middle loving” temperature microbes. They grow best between 20-24 C

81
Q

What are psychrotrophs?

A

Microbes that like cool environments that range from 4-25 C

82
Q

What are psychrophiles?

A

microbes that are cold-loving and grow in places 0 C and below

83
Q

How are psychrophiles membranes adapted to their preferred environment?

A

The lipids in their membranes tend to be unsaturated to increase fluidity

84
Q

What is quorum sensing?

A

Mechanism by which cells in a biofilm coordinate their activities in response to environmental stimuli. Microorganisms send signals (autoinducers) until they reach a threshold ( a quorum). This in turn activates genes associated with cellular functions that are beneficial only when the population reaches a critical density.

85
Q

What is ROS

A

Reactive oxygen species – unstable ions and molecules derived from partial reduction of oxygen that can damage virtually any macromolecule or structure with which they come in contact

86
Q

What 3 enzymes are needed to break down ROS

A
  1. superoxide dismutase (SOD)
  2. peroxidase
  3. catalase
87
Q

What are obligate aerobes?

A

microbes that must need oxygen

88
Q

What are microareophiles?

A

microbes that require a minimum level of oxygen for growth

89
Q

What are Facultative anaerobes

A

Organisms that thrive in the presence of oxygen, but also grow in its absence by relying on fermentation or anaerobic respiration

90
Q

What are aerotolerant anaerobes?

A

microbes that are indifferent to oxygen; they don’t use oxygen, but are not harmed by its present

91
Q

What are obligate anaerobes

A

microbes that require no oxygen and will even be killed by oxygen

92
Q

What does acidophile, neutrophile, and alkaliphile mean?

A

microbes that grow at acidic pH values, neutral pH values, and basic pH values

93
Q

What are two examples of common biofilms?

A
  1. plaque
  2. pseudomonas aeruginosa often colonizes
94
Q

What are the two types of glycocalyces?

A

Capsule: An organized layer located outside the cell wall and usually composed of polysaccharides or proteins
Slime layer: a less tightly organized layer that is only loosely attached to the cell wall and can be easily washed off

95
Q

What is the purpose of glycocalyces?

A

They allow bacterial cells to adhere to surfaces, aiding to the formation of biofilms

96
Q

What is an S-layer?

A

another type of bacterial cell envelope structure composed of a mixture of structural proteins and glycoproteins. Exact function is not known, but some studies suggest they might help the cell withstand osmotic pressure.

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