Topic 8

Question 1

Human microbiota

Answer 1

collection of microbes in/living on us

Question 2

Human microbiome

Answer 2

microbiota and the environment(s) they live in

Question 3

“Microbial flora”

Answer 3

basically used in the same sense as microbiota

Question 4

Dysbiosis

Answer 4

used to describe an altered microbiota that is unhealthy for the host

• out of balance
• loss of important commensals
• increase in microbes associated with disease

Question 5

What alters the microbiome?

Answer 5

diet, exercise, antibiotics, etc.

Question 6

T or F. Most members of human microbiota are not culturable

Answer 6

T, vast majority of out knowledge comes from DNA sequencing (16S, shot gun)

Question 7

Animal models

Answer 7

• germ-free animals then introduce microbes

- no model is perfect but we learn los from these!

Question 8

Things we have learned lots about

Answer 8

• Links between microbiota composition and health/disease
• composition of microbiota – how it changes over time
• factors influencing composition

Question 9

Things we know very little about

Answer 9

• community dynamics; how microbes interact
• whether links b/w microbiota/disease CAUSAL or only correlative
• potential mechanisms linking microbiota and disease
• how to introduce a healthy microbiome to an individual with dysbiosis

Question 10

Mucus

Answer 10

thick, slippery suspension that includes antimicrobial factors and mucin (gel-like glycoprotein substance, serves a barrier function)

Question 11

Gram negative bacteria – masters of complex carbohydrate metabolism

Answer 11

Bacteriodetes

Question 12

Very diverse phylum of gram positive bacteria

Answer 12

Firmcutes

Question 13

Proteobacteria

Answer 13

• generally facultative anaerobes
• rapidly consume any O2 present
• important for maintaining anaerobic environment
• high proportions = dysbiosis?

Question 14

IBS

Answer 14

high proportion of proteobacteria

Question 15

Primary fermenter in gut microbiota

Answer 15

• many species but especially Bacterioetes

- can ferment diverse carbs from food or mucin

Question 16

Fermentation products in gut microbiota by primary fermenters

Answer 16

some absorbed by short chain fatty acids (host) or feed other microbes (syntrophy)

Question 17

Probiotic

Answer 17

liv microorganisms that when administered, have beneficial effect on host; consuming “ good bacteria”

Question 18

Prebiotic

Answer 18

a substance that when consumed, promotes the growth of beneficial microbes; can be simple and effective (eg: fibre in diet)

Question 19

T or F. We have neutral/beneficial interactions with the vast majority of microbes we interact with

Answer 19

T! although rare, many different bacteria can cause disease (also eukaryotic microbial pathogens); no known archaeal pathogens

Question 20

Infection

Answer 20

invasion of body by a disease-causing organism; can be asymptomatic, or can result in different disease (NOT same thing as disease)

Question 21

Disease

Answer 21

damage or injury to host organism (overt symptoms); some bacteria cause disease without establishing an infection (TOXINS)

Question 22

Pathogen

Answer 22

an organism that causes disease

Question 23

Pathogenesis

Answer 23

mechanism that leads to disease

Question 24

Virulence

Answer 24

similar to pathogenicity, but often used to describe the severity of the disease (“highly virulent”)

Question 25

Inflammation

Answer 25

body's immune response to infection or injury -- important part of how we clear infections

Question 26

Symptoms of bacterial diseases

Answer 26

- can be from activities of pathgoens (toxins, tissue damage, etc.) - or caused by our immune response to the pathogen (fever, redness, swelling, etc)

Question 27

Adherence: Colonization: Invasion: Spread

Answer 27

Adherence: binding; foothold Colonization: expanding population (planktonic or biofilm) Invasion: gain access to privileged sits ( penetrate mucus membranes) Spread: does not always occur; moving beyond initial site of infection

Question 28

Uncontrolled systematic spread

Answer 28

via bloodstream; often results in very serious infections/disease

Question 29

This is often key to establishing an infection

Answer 29

- adherence; microbes generally target specific cells or tissue types (adhered to specific receptors on cells -- glycoproteins or glycolipids)

Question 30

Adherence factors

Answer 30

- pili, fimbriae, adhesins, surface proteins, capsules

Question 31

Mucous membranes

Answer 31

tightly packed cell layers covered with a mucous layer; important protective layer

Question 32

Invasion

Answer 32

ability of pathogen to enter host cells and/or tissues; penetrate beyond where microbes (microbiota) normally reside

Question 33

Virulence factors

Answer 33

molecules | (typically proteins) produced by a pathogen that contributes to its ability to cause disease

Question 34

Common types of virulence factors

Answer 34

- adhesion factors - nutrient acquisition (siderophores -- capture iron) - immune resistance (eg: resistance to reactive O2 species) - immune evasion/disruption (hides microbe from immune system or disrupts the function of immune system - extracellular enzymes, protein secretion systems/effectors, and toxins that damage host cells and/or manipulate host cell biology

Question 35

DNA polymerase

Answer 35

required for bacteria to cause disease or LIVE so not considered a virulence factor

Question 36

Virulence factors: Immune evasion

Answer 36

- hide inside cells (intracellular) - capsule: hide surface antigens; prevent detection; can be sugar or proteins - some hide pathogen associated molecular patterns (PAMPs) like LPS (triggers immune response)

Question 37

Virulence factors: extracellular enzymes

Answer 37

secreted or surface enzyme that can promote virulence in different ways: - provide free up nutrients - damage host cells - inactivate immune cell mechanisms - disrupt barriers to enable pathogen invasion/spread

Question 38

Streptokinase vs Coagulase

Answer 38

- both secreted enzyme virulence factors - --> Coagulase: induces clots to prevent immune detection (S. aureus) - --> Streptokinase: dissolves clots, enabling pathogen to spread (S. pyogenes)

Question 39

Exotoxins

Answer 39

- similar to bacteriocins, but target host - among the most important virulence factors - we knew about some toxins as soon as we knew about bacteria causing disease - not all produce toxins; some produce multiple

Question 40

Alpha toxin from S. aureus

Answer 40

- polymerize in host cell membrane to form a pore - can have a range of effects: cell lysis to signalling changes - major effect on virulence of S. aureus strains ; this isn't the disease though just less virulent without this

Question 41

AB-type toxins

Answer 41

- target some aspect of biology inside cell; need to cross the host cell membrane - A subunit exerts biological effect; generally, modify or degrade specific molecules (typically host cell protein) - B subunit bind host cell receptor (usually glycolipid/glycoprotein) to mediate uptake - AB5 toxins: pertussis, cholera, O157:H7,

Question 42

C. botulinum

Answer 42

- rarely infects adult humans; but grows/ produce toxins on food we consume - AB-type toxin - B subunit targets motor neurons - A subunit is a protease that cleaves specific NARE proteins that are required by cells to release Ach - absence of Ach --> muscle paralysis - one of the most deadly substances known (0.1 microgram can kill you) - VERY POTENT; game over even if one toxin gets in

Question 43

Toxoids

Answer 43

inactivated toxins as vaccines

Question 44

T or F. toxins can be used to treat non-bacterial disease

Answer 44

T, since they efficiently manipulate human biology in a targeted way ; ex: botox (migraines, cerebral palsy, etc); relaxes muscles

Question 45

Effector proteins vs toxins

Answer 45

Toxins can be produced at a certain site of infection and can act elsewhere Whereas, secretion systems; bacteria has to be present to physically inject Toxins often more potent and ca lone, whereas effectors are part of a bigger biological program

Question 46

Yersinia pestis

Answer 46

- plague - gram neg proteobactrium - rodents; caused by disease vector (fleas -- survives in fleas); humans are incidental or emergency host - person-to-person spread (lice?)

Question 47

Types of plague

Answer 47

- bubonic: infection of lymph nodes - pneumonic: infection of lungs - septicemic plague: bloodstream (rare); bacterial spread ^^ all have high mortality rates is untreated; bubonic most common and pneumonic/septicemic death rates =100% if untreated