Adhesion and Invasion

Question 1

What is adherence essential for both extracellular and intracellular bacteria?

Answer 1

Extracellular: adherence allows bacteria to resist the mechanical clearing mechanisms of the host
Intracellular: pre-requisite for uptake or invasion

Question 2

What are adhesions?

Answer 2

Bacterial components that mediate interaction between the bacterium and the host cell surface

Question 3

How do adhesions bind to host cells?

Answer 3

They bind specifically to host cell surface receptors
There is a high degree of specificity between adhesion and the host recognition site

Question 4

What are host surface glycans used for?

Answer 4

Receptors for bacterial adhesions as bacteria can specifically recognize and adhere to sugars

Question 5

What are pili?

Answer 5

Fragile, hairlike adhesions that are frequently replaced and thus have a high potential for variation

Question 6

How do pili hide their antigenic site?

Answer 6

The are highly glycosylated which allows for velcro-like attachment to surfaces

Question 7

What are Type 1 pili and what Gram stain are they found on?

Answer 7

Rigid, long (0.5-10 micrograms), and thin filaments that protrude off Gram-negative bacteria

Question 8

What is a unique feature of type 1 pili?

Answer 8

They induce hemagglutination

Question 9

How are type 1 pili assembled and by which pathways?

Answer 9

Composed of polymerized subunits of the pilin protein = sec-transport pathway
Chaperone-usher pathway assembles proteinaceous filaments of bacterial surfaces

Question 10

What do type 1 pili operons, at minimum, encode?

Answer 10

Chaperones, usher, and pilin

Question 11

What are F1 pili?

Answer 11

Short, linear, and flexible polymers that have a tendency to aggregate

Question 12

What are F1 capsular antigens exclusively expressed by and what is its function?

Answer 12

Y. pestis
Anti-phagocytic which prevents uptake by macrophages

Question 13

What is a similarity between F1 pili and type 1 pili?

Answer 13

They both use the CU system

Question 14

What does the F1 capsule consist of and what is its characteristic?

Answer 14

A tangle of thin, linear Caf1 fibers
Lots of variabilities = limited vaccine development

Question 15

What are 3 examples of bacteria with type IV pili?

Answer 15

EPEC
N. gonorrhoeae
N. meningitidis

Question 16

What does the binding of EPEC cause?

Answer 16

Upregulation of virulence genes in bacterium and retraction of the pilus

Question 17

What do type IV fibers recognize?

Answer 17

Host cell sugars

Question 18

What can EPEC and V. cholerae type IV pili do?

Answer 18

Aggregate laterally forming bundles

Question 19

How does twitching motility work?

Answer 19

Surface motility powered by the extension and retraction of type IV pili, which confers slow cell movement that appears jerky

Question 20

What is motility required for in type IV pili?

Answer 20

Required for virulence and may help engage the type II secretion systems for the injection of toxins

Question 21

What is microbial dysbiosis on the teeth facilitated by?

Answer 21

A shift in the microbiome towards Gram-negative anaerobes

Question 22

What is the keystone pathogen causing periodontal disease and is this pathogen alone sufficient to cause the disease?

Answer 22

P. gingivalis
It is not sufficient on its own but instead facilitates an ecological change to a disease state

Question 23

How dos P. gingivalis act as a keystone pathogen?

Answer 23

By the production of a virulence factor called gingipain (cysteine protease)

Question 24

How does gingipain work?

Answer 24

It cleaves complement C5 protein into C5a which activates the C5a receptor and increase the inflammatory response but at the same time prevents microbial killing by leukocytes

Question 25

Which pili are the only ones that can bind DNA?

Answer 25

Type IV

Question 26

What does DNA transformation from N. meningitidis require the presence of?

Answer 26

Short DNA uptake sequences residing in coding regions of the donor DNA

Question 27

What does transferred DNA often contain?

Answer 27

Virulence genes including toxin resistance and antibiotic resistance

Question 28

Where do meningococcal type IV pili bind DNA?

Answer 28

Through the minor pilin ComP which is a highly conserved component throughout Neisseria species

Question 29

What do type IV pili promote?

Answer 29

The attachment to a variety of chemically diverse surfaces

Question 30

What are biofilms?

Answer 30

Dense, multi organismal layers of bacterial communities attached to surfaces

Question 31

What is the attachment of biofilms to surfaces mediated by?

Answer 31

Extracellular polysaccharide slime (EPS)

Question 32

What are the primary colonizers of biofilms?

Answer 32

Clostridia spp and P. aeruginosa

Question 33

What is P. aeruginosa and what does it cause?

Answer 33

A typically nosocomial, opportunistic pathogen It causes UTIs, respiratory infections, and GI infections

Question 34

What is the natural habitat of P. aeruginosa?

Answer 34

Ubiquitous in soil and water

Question 35

What is the metabolism of P. aeruginosa like?

Answer 35

Metabolically diverse, can be aerobic or anaerobic Can grow on 75 different organic substrates

Question 36

What are the nutritional requirements of P. aeruginosa?

Answer 36

Minimal nutritional needs

Question 37

What is the optimal growth temperature of P. aeruginosa?

Answer 37

Wide temperature range, 0-37 degrees

Question 38

What is the tolerance of P. aeruginosa to physical conditions like?

Answer 38

Often grows in biofilms Resistant to detergents and high salt

Question 39

How is P. aeruginosa resistant to antibiotics and phagocytes?

Answer 39

Antibiotic-resistant genes have evolved Association with biofilm

Question 40

What does P. aeruginosa produce to adhere to the host or other surfaces?

Answer 40

Type IV pili

Question 41

What is the process of biofilm formation?

Answer 41

Type IV pili produce EPS Association with type IV pili with a substrate activates PSl genes which are involved in the formation of the biofilm The early stages of biofilm formation have low levels of EPS and is reversible at this point The accumulation of EPS causes a thick biofilm that allows for immune invasion and resistance to insults

Question 42

What are PSl genes?

Answer 42

Polysaccharide synthesis locus genes

Question 43

What do sortase enzymes do?

Answer 43

Catalyze the transpeptidation of pilin synthesis, linking of amino acids

Question 44

What is an important virulence factor for Gram-positive bacteria?

Answer 44

Sortase enzymes

Question 45

How are Gram-positive pili formed?

Answer 45

By covalent attachment of pilin subunits to each other and to the peptidoglycan layer

Question 46

What do prokaryotic sortase enzymes promote?

Answer 46

The covalent anchoring of surface proteins to the cell wall envelope to enable each microbe to effectively interact with its environment

Question 47

What are the main functions of sortases?

Answer 47

Cleave surface proteins and allow rearrangements and modifications Sorts proteins of the cell surface and covalently links to the cell wall Polyermizes pilin proteins

Question 48

What are the symptoms of diphtheria?

Answer 48

Sore throat Grey patches in the throat Barking cough

Question 49

How many sortase enzymes does C. diphtheriae encode and how many does it actually need?

Answer 49

Encodes 6, only needs one

Question 50

What is the purpose of SpaA?

Answer 50

Produces shaft of the pilus (type III)

Question 51

What is SrtA?

Answer 51

The sortase that polymerizes pilus

Question 52

What is SpaB?

Answer 52

Surface proteins

Question 53

What is SpaC for?

Answer 53

Tip adhesion

Question 54

What is the purpose of SrtF?

Answer 54

Housekeeping sortase that anchors pili into the cell wall

Question 55

What system exports pilin proteins?

Answer 55

Sec transport system

Question 56

How does S. aureus disguise itself?

Answer 56

Sortases function to attach immunoglobulins to the surface of the bacteria

Question 57

Can mutants of SpaA cause infection?

Answer 57

No

Question 58

What do non-pili adhesins facilitate?

Answer 58

Tighter binding of bacteria to host cells after initial binding by pili

Question 59

What type of bacteria are non-pili adhesions common in?

Answer 59

Gram-positive food-borne pathogens

Question 60

What is YadA and what does it promote?

Answer 60

A collagen-binding outer membrane protein that promotes cell adhesion to eukaryotic host and virulence

Question 61

How does YadA protect bacteria?

Answer 61

Binding ECM Temperature sensitive expression Pro-phagocytic

Question 62

Which bacteria is YadA found in?

Answer 62

Y. pestis Y. pseudotuberculosis Y. enterocolitica

Question 63

What are 3 virulence factors of Yersinia?

Answer 63

LPS YadA Invasin

Question 64

What is the difference between YadA and invasin?

Answer 64

YadA interacts indirectly with integrins though binding of the ECM Invasin interacts directly with integrins

Question 65

What do YadA and invasin trigger?

Answer 65

Entry into phagocytes as invasin zippers host membrane around it

Question 66

What do many pathogens do once adhered?

Answer 66

Use the cell's own cytoskeleton to invade the target cell either by triggering phagocytosis or by using the cytoskeleton to migrate through the cell

Question 67

What are the main adhesins and receptors in Listeria?

Answer 67

Adhesions = internalin A (InlA) and internalin B (INlB) Receptors = E-cadherin and Met

Question 68

What are E-cadherin and Met components of?

Answer 68

Eukaryotic intracellular junctions

Question 69

What exactly are InlA and InlB and what do they do?

Answer 69

Afimbrial adhesins Necessary and sufficient to trigger host cell entry

Question 70

What does the entry of L. monocytogenes into cells require?

Answer 70

Requires action polymerization and membrane remodeling

Question 71

What does L. monocytogenes manipulate to its advantage?

Answer 71

Host-cell signaling and endocytic pathways

Question 72

What do actin rearrangements due to the binding of listeria form?

Answer 72

Pseudopodia

Question 73

What does listeria binding to the host cause and what does it facilitate?

Answer 73

Microfilament rearrangement and it facilitates phagocytosis

Question 74

Where does listeria thrive?

Answer 74

In phagosomes

Question 75

What does InlA induce?

Answer 75

Cytoskeletal rearrangements in the host cell for uptake of listeria by epithelial cells = virulence factor

Question 76

What is E-cadherin and what binds to its extracellular domain?

Answer 76

Host protein Transmembrane, cell-cell adhesion molecule InlA binds to the extracellular domain

Question 77

Assembly and attachment of what is central to intercellular adhesion and Listeria entry?

Answer 77

E-cadherin, alpha-catenin, beta-catenin