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Microbiology > Lecture 2 structures > Flashcards

Lecture 2 structures Flashcards

1
Q

How are flagella assembled?

A

In a step-by-step manner using a specialized protein secretion pathway called type 3 secretion

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2
Q

How fast can flagella go?

A

Up to 100mph

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3
Q

Describe the use of flagella in H. Pylori

A

H. Pylori will create a “sheath” of flagella using synthesized sugar; the most vulnerable point of a flagella is its very tip, so they have extra proteins that create a “terminal bulb” at the ends of the flagella.

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4
Q

Coordinated counterclockwise motion of flagella leads to swimming, and is a(n) __________
Clockwise motion of flagella leads to tumbling, and is a(n) _________.

A

Counterclockwise swimming is an attractant; clockwise tumbling is a repellent

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5
Q

Define chemotaxis

A

Swimming motility; movement toward or away

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6
Q

Describe the structure of flagella

A

1) There’s a protein structure across the envelope, called the basal body or rotor.
2) Just above the basal body there’s a hook, called a universal joint
3) The filament acts as a propeller

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7
Q

What are flagella driven by?

A

Ionic potential/ proton motive force

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8
Q

The motor that turns the flagella rotates on average _____ rpm.
E. coli = ______rpm
Vibrio = ______rpm

A

500; E. coli is 5,000rpm; Vibrio is 100,000rpm

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9
Q

How does flagella motion activate for chemotaxis?

A

Chemoreceptors in envelope relay information to flagellar apparati, so the flagella turn on when the bacteria senses food

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10
Q

Why is adherence so important to bacteria?

A

Provides an advantage, prevents removal by fluids

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11
Q

True or false: Virtually all pathogenic bacteria having ways of attaching themselves firmly to host cells

A

True

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12
Q

Define pili (fimbriae) and what they do

A

Defined as filamentous appendages composed of “pilin” protein that are anchored to the outer membrane of Gram negative bacteria
-Mediate attachment to eukaryotic host cells

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13
Q

Pili are primarily found in Gram-________ bacteria

A

negative

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14
Q

Pili are peritrichou; define peritrichou

A

Hairy all over

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15
Q

Give an example of a specialized pili

A

Sex or F pilus for bacterial conjugation

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16
Q

What can be described as “rod-shaped protein structures extend from the bacterial surface and bind to host cell surface molecules (typically carbohydrates.)”?

A

Pili

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17
Q

True or false: Pili can be evenly distributed or located preferentially to one part of the bacterial cell.

A

True

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18
Q

Define afimbrial adhesins. What kind of bacteria are they found in?

A

-Defined as bacterial surface proteins that are not organized in a rodlike structure and mediate tight binding between bacteria and host cell.
-All bacteria have these

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19
Q

Bacteria may produce both pili and afimbrial adhesins. Why?

A

To lock into the surface if it’s in an area of fast flow

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20
Q

Define capsules

A

Capsules are an enormous layer of polysaccharides

(With the exception of Bacillus anthracis poly-D glutamic acid, a polypeptide capsule)

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21
Q

What does the capsule of bacteria do?

A

It’s anti-phagocytic; it’s also called the K-antigen and has thousands of serotypes

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22
Q

What is the K antigen?

A

Capsules

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23
Q

Define glycocalyx and what it does

A

-Also known as the slime layer, it’s a “loose” layer of polysaccharides
-It functions in attachment/adherence/motility and is a key feature of biofilm formation

24
Q

What is a key feature of biofilm formation?

A

Glycocalyx

25
Q

Define the S-layer and what it does

A

-A layer composed of a single protein species [sometimes glycosylated] that forms a crystalline array
-This layer is small; you’d need electron microscopy to observe it
-Aids in protection against environmental stress (osmotic, pH, enzymatic) and in phagocytosis

26
Q

Lipopolysaccharide (LPS) is found on the surface of Gram-________ bacteria; it is not present on the other type of Gram bacteria

A

negative

27
Q

Name and describe the 3 regions of lipopolysaccharides (LPS)

A

1) Lipid A domain: phosphorylated lipid with sugar backbone
2) Core region: oligosaccharide chain
3) O-antigen: polysaccharide chain

28
Q

Describe the role of the lipid A domain (region I) of lipopolysaccharides (LPS)

A

-Hydrophobic anchor, holds LPS in the outer membrane.
-The portion of LPS responsible for endotoxicity
-Activates Toll-receptor (innate immune response)
–Changing the lengths of the acyl chains, changing the number of acyl chains, adding ethanolamine/phosphate/etc to the phosphate groups to alter its surface charge, or adding amino acids to Lipid A can prevent Lipid A from activating the Toll-receptor
-Important: Some bacteria synthesize a non-inflammatory lipid A to evade immune recognition

29
Q

What is the portion of LPS responsible for endotoxicity?

A

The lipid A domain (region I)

30
Q

What activates the Toll-receptor?

A

Lipid A domain

31
Q

Describe the role of the core oligosaccharide region (region II) of lipopolysaccharides (LPS)

A

-Consists of short chain of sugars attached directly to lipid A
-Not required for growth in laboratory
-Clinical Relevance: During infection thought to be required for maintaining permeability properties of the outer membrane

32
Q

Describe the role of the O-antigen/ O-polysaccharide region (region III) of lipopolysaccharides (LPS)

A

-Repeating unit of oligosaccharide subunits made up of 3-5 sugars attached directly to the outer core region (up to 40 units long)
-Major antigenic determinant with great variation between species and even strains
-Used as basis for determining serogroup of a bacterial strain
-Clinical Relevance: Loss of O-antigen results in loss of virulence; O-antigen provides protection from host defenses

33
Q

The loss of what part of a lipopolysaccharide leads to loss of virulence?

A

The O-antigen; it provides protection from host defenses

34
Q

Give 5 examples of internal structures found in bacteria

A

Gas vacuole, ribosomes, inclusions, nucleoid, endospore

35
Q

What is the purpose of a gas vacuole?

A

Buoyancy for floating in aquatic environments

36
Q

What is the purpose of ribosomes?

A

Protein synthesis

37
Q

What is the purpose of inclusions?

A

Storage of carbon, phosphate, and other substances

38
Q

What is the purpose of the nucleiod?

A

Localization of genetic material (DNA)

39
Q

What is the purpose of an endospore, and in what type of bacteria are they found?

A

-Survival under harsh environmental conditions; only observed in bacteria
-Specifically only some gram-positive bacteria

40
Q

What are the 3 main components of the bacterial cytoskeleton, and what do they do?

A

1) FtsZ: A division protein widely observed in bacteria; forms a disc shape in the center of the cell
2) MreB: maintains cell (rod) shape, localizes proteins
3) Crescentin: introduces crescent-shaped morphology

41
Q

Name and briefly describe the density of 3 storage inclusions found in bacteria

A

1) Glycogen (sugar)
2) Polyhydroxyalkanoate granules: Very light
3) Polyphosphate granules: Very dense; store phosphate

42
Q

What is the purpose of vacuoles?

A

To store gas for buoyancy in an aquatic environment

43
Q

What do magnetosomes do?

A

Aid in orientation to seek nutrients; based on earth’s magnetic poles

44
Q

What is the purpose of carboxysomes?

A

A specialized site for CO2 fixation (a protein coat with an enzyme inside)

45
Q

There are as many as ________ ribosomes growing in a bacterial cell, whereas eukaryotes have up to ________

A

70K; 10 million

46
Q

Why is the difference in size and composition between a prokaryote and eukaryote important?

A

It’s important for antibiotics; they can pick out bacterial ribosomes and keep them from synthesizing proteins

47
Q

Describe bacterial nucleiods

A

-Most are circular
-No membrane
-Have proteins and histone-like proteins that interact and organize things

48
Q

Name 3 types of bacterial plasmids and briefly describe what they do

A

1) Conjugative plasmids: the F factor; transfers copies of themselves into another bacteria
2) R (resistance) plasmids: can be conjugative (transfered through bacterial “sex”); delivers antibiotic resistance genes
3) Virulence plasmids: encode genes for pathogenicity

49
Q

Some Gram-_________ bacteria are spore-formers

A

positive

50
Q

What is the purpose of sporulation, and what do spores contain?

A

1) Spores represent a dormant state for long-term survival; formation (sporulation) is induced by harsh environmental conditions
2) Spores contain the entire chromosome enveloped by a membrane, peptidoglycan and an outer protein coat (keratin-like)

51
Q

Certain conditions will cause spores to become activated; this is called _____________

A

germination

52
Q

What aspect of sporulation is useful in diagnosis?

A

The location of endospores

53
Q

Name 4 locations of endospores

A

1) Central
2) Swollen sporangium (makes cell somewhat sperm-shaped)
3) Terminal (at the end of a rod-cell)
4) Subterminal (almost at the end of a rod-cell)

54
Q

Why do we typically set autoclaves to 121 degrees celcius?

A

That’s the temperature that can kill endospores

55
Q

Briefly describe the morphology of protozoa, amoeba, and algae

A

Protozoa: motile due to cilia that cover their surface, heterotrophs
Amoeba: has a pseudopod and a contractile vacuole to control movement; prevents excess water inside the cell
Algae: have stored starch grains so they have carbon on-demand, use sunlight’s energy or can use organic compounds, extreme diversity, extremely abundant

56
Q

Define siderophore and what it allows bacteria to do

A

-A molecule that binds to various forms of iron and makes it available to the cell
-This allows bacteria living in an animal to steal that creature’s iron

Microbiology (42 decks)

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