Lecture 2 structures

Question 1

How are flagella assembled?

Answer 1

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

Question 2

How fast can flagella go?

Answer 2

Up to 100mph

Question 3

Describe the use of flagella in H. Pylori

Answer 3

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.

Question 4

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

Answer 4

Counterclockwise swimming is an attractant; clockwise tumbling is a repellent

Question 5

Define chemotaxis

Answer 5

Swimming motility; movement toward or away

Question 6

Describe the structure of flagella

Answer 6

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

Question 7

What are flagella driven by?

Answer 7

Ionic potential/ proton motive force

Question 8

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

Answer 8

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

Question 9

How does flagella motion activate for chemotaxis?

Answer 9

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

Question 10

Why is adherence so important to bacteria?

Answer 10

Provides an advantage, prevents removal by fluids

Question 11

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

Answer 11

True

Question 12

Define pili (fimbriae) and what they do

Answer 12

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

Question 13

Pili are primarily found in Gram-________ bacteria

Answer 13

negative

Question 14

Pili are peritrichou; define peritrichou

Answer 14

Hairy all over

Question 15

Give an example of a specialized pili

Answer 15

Sex or F pilus for bacterial conjugation

Question 16

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

Answer 16

Pili

Question 17

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

Answer 17

True

Question 18

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

Answer 18

-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

Question 19

Bacteria may produce both pili and afimbrial adhesins. Why?

Answer 19

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

Question 20

Define capsules

Answer 20

Capsules are an enormous layer of polysaccharides

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

Question 21

What does the capsule of bacteria do?

Answer 21

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

Question 22

What is the K antigen?

Answer 22

Capsules

Question 23

Define glycocalyx and what it does

Answer 23

-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

Question 24

What is a key feature of biofilm formation?

Answer 24

Glycocalyx

Question 25

Define the S-layer and what it does

Answer 25

-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

Question 26

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

Answer 26

negative

Question 27

Name and describe the 3 regions of lipopolysaccharides (LPS)

Answer 27

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

Question 28

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

Answer 28

-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

Question 29

What is the portion of LPS responsible for endotoxicity?

Answer 29

The lipid A domain (region I)

Question 30

What activates the Toll-receptor?

Answer 30

Lipid A domain

Question 31

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

Answer 31

-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

Question 32

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

Answer 32

-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

Question 33

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

Answer 33

The O-antigen; it provides protection from host defenses

Question 34

Give 5 examples of internal structures found in bacteria

Answer 34

Gas vacuole, ribosomes, inclusions, nucleoid, endospore

Question 35

What is the purpose of a gas vacuole?

Answer 35

Buoyancy for floating in aquatic environments

Question 36

What is the purpose of ribosomes?

Answer 36

Protein synthesis

Question 37

What is the purpose of inclusions?

Answer 37

Storage of carbon, phosphate, and other substances

Question 38

What is the purpose of the nucleiod?

Answer 38

Localization of genetic material (DNA)

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

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

Answer 41

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

Question 42

What is the purpose of vacuoles?

Answer 42

To store gas for buoyancy in an aquatic environment

Question 43

What do magnetosomes do?

Answer 43

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

Question 44

What is the purpose of carboxysomes?

Answer 44

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

Question 45

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

Answer 45

70K; 10 million

Question 46

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

Answer 46

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

Question 47

Describe bacterial nucleiods

Answer 47

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

Question 48

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

Answer 48

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

Question 49

Some Gram-_________ bacteria are spore-formers

Answer 49

positive

Question 50

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

Answer 50

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)

Question 51

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

Answer 51

germination

Question 52

What aspect of sporulation is useful in diagnosis?

Answer 52

The location of endospores

Question 53

Name 4 locations of endospores

Answer 53

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)

Question 54

Why do we typically set autoclaves to 121 degrees celcius?

Answer 54

That's the temperature that can kill endospores

Question 55

Briefly describe the morphology of protozoa, amoeba, and algae

Answer 55

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

Question 56

Define siderophore and what it allows bacteria to do

Answer 56

-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