Module 10: Microbe-Host Interactions

Question 1

What is a microbiome?

Answer 1

a functional collection of different microbes in a particular environmental system.

Question 2

What is a microbiota?

Answer 2

all the microbes in a microhabitat

Question 3

How many microbes are in the human microbiome?

Answer 3

10¹³

Question 4

What are the benefits of knowing the human microbiome?

Answer 4

• development of biomarkers for predicting predisposition to diseases
• designing targeted therapies
• personalized drug therapies and probiotics

Question 5

What are the six microbial habits of the human body?

Answer 5

• skin
• airways
• oral
• skin
• gut
• vagina

Question 6

List the bacterial group that predominates at each of the following body sites:

1. Skin
2. Saliva
3. Urogenital tract
4. Gastrointestinal tract

Answer 6

1. Propionibacterium (Gram +)
2. Streptococcus (Gram +)
3. Lactobacillus (Gram +)
4. Bacteroidetes (Gram +)

Question 7

What is disbiosis?

Answer 7

an imbalance in the quantity and type of microorganisms in the human microbiome (ex. cause: taking antibiotics)

Question 8

What are the objectives of the Canadian Human Microbiome Initiative?

Answer 8

• characterize the microorganisms colonizing the human body
• evaluate their relationship to health
• examine compositional changes associated with chronic disease

Question 9

Microbes in the gut affect:

Answer 9

• early development
• health
• predisposition to disease

Question 10

The bacterial numbers in the gut increase from 10² to 10¹² as pH increases or decreases?

Answer 10

Increases

Question 11

Firmicutes, Bacteroides and Actinobacteria are common in:

Answer 11

gastric fluid

Question 12

Firmicutes and Proteobacteria are common in:

Answer 12

the mucus layer of the stomach

Question 13

This acid-resistant bacteria causes chronic and acute gastritis and leads to the formation of peptic ulcers.

Answer 13

Helicobacter pylori

Question 14

98% of all human gut phylotypes fall into one of thre major bacterial phyla:

Answer 14

• firmicutes
• bacteroidetes
• proteobacteria

Question 15

Peptide antibiotics that contain unusual amino acids; synthesized by Gram + bacteria.

Answer 15

lantibiotics

Question 16

What are bacteriocins?

Answer 16

antibacterial products

Question 17

These two small bioactive molecules produced by bacteria in the large intestine, help bacteria to maintain a niche in the body or inhibit the growth of transient bacteria.

Answer 17

• lantibiotics
• bacteriocins

Question 18

The three prominent phyla in the oral cavity:

Answer 18

• firmicutes
• proteobacteria
• bacteroidetes

Question 19

What are the defense mechanisms of the oral cavity?

Answer 19

• lysozyme in saliva, which cleaves glycosydic linkages in the cell wall
• mucous membranes promote the growth of normal bacteria and can inhibit pathogens
• secretes mucin which helps mucous layer retain moisture and inhibits attachment of bacteria to epithelial cells

Question 20

Which microbe is the first to colonize on the tooth surface?

Answer 20

streptococcus

Question 21

_________ is a major contributor to the biofilm called dental plaque. It generates lactic acid that wears down tooth enamel.

Answer 21

Streptococcus mutans

Question 22

Altered pH conditions can cause potential pathogens in the urethra to multiply and cause disease. These two pathogens frequently cause UTIs.

Answer 22

• Escherichia coli
• Proteus mirabilis

Question 23

___________, is a resident organism of the vagina that ferments glycogen producing lactic acid. The lactic acid maintains a local acidic environment.

Answer 23

Lactobacillus acidophilus

Question 24

The four predominant phyla of the skin are:

Answer 24

• actinobacteria
• firmicutes
• proteobacteria
• bacteroidetes

Question 25

The most abundant viruses in all body sites are not animal viruses by instead are \_\_\_\_\_\_\_\_\_\_\_\_.

Answer 25

bacteriophages

Question 26

What are Koch's postulates?

Answer 26

1. the suspected causative agent must be absent from all healthy organisms but present in all diseased organisms. 2. the causative agent must be isolated from the diseased organism and grown in pure culture 3. the cultured agent must cause the same disease when inoculated into a health susceptible organism. 4. the same causative agent must then be reisolated from the inoculated diseased organism.

Question 27

Microbial parasites that cause disease or tissue damage in a host.

Answer 27

Pathogens

Question 28

The ability of a parasite to inflict damage on the host.

Answer 28

Pathogenicity

Question 29

Relative ability of a pathogen to cause disease (measure of pathogenicity)

Answer 29

Virulence

Question 30

Causes disease only in the absence of normal host resistance.

Answer 30

Opportunistic Pathogen

Question 31

Situation in which a microorganism is established and growing in a host, whether or not the host is harmed.

Answer 31

Infection

Question 32

Damage or injury to the host that impairs host function.

Answer 32

Disease

Question 33

After to exposure to pathogens, that are the steps of the infection process that follow?

Answer 33

* Adherence - to skin or mucous * Invasion - through epithelium * Multiplication - growth and production of virulence factors and toxins.

Question 34

The enhanced ability of microbes to attach to host tissues.

Answer 34

Adherence

Question 35

Bacteria and viruses that initiate infection often adhere specifically to _____________ through macromolecular interactions on the surfaces of the pathogen and the host cell.

Answer 35

Epithelial cells

Question 36

Glycoproteins or lipoproteins found on the pathogen's surface that enable it to bind to host cells.

Answer 36

Adhesins

Question 37

*N. gonorrhoeae* adheres to mucosal epithelial cells using the __________ and \_\_\_\_\_\_\_\_.

Answer 37

* opa protein * pili

Question 38

Influenza virus binds cells via it's \_\_\_\_\_\_\_\_\_\_\_.

Answer 38

haemagglutinin

Question 39

What is SdrG (serine-aspartate dipeptide repeats)

Answer 39

an adhesin protein found in Gram + pathogens that binds fibrinogen.

Question 40

The bacterial capsule forms a thick coating outside the plasma membrane and cell wall and serves two important functions in bacterial pathogenicity:

Answer 40

1. the capsule is both stick and contains specific receptors to **facilitate attachment** on host tissues 2. capsules **protect the bacteria from ingestion** by white blood cells

Question 41

Three bacterial cell surface protein structures that function in attachment:

Answer 41

* fimbriae * flagella * pili

Question 42

The ability of a pathogen to spread and cause disease.

Answer 42

Invasion

Question 43

Pathogens produce various virulence factors that enhance invasiveness:

Answer 43

* **enzymes** that enhance virulence by breaking down or altering host tissue to provide access to nutrients (ex. hyaluronidase, collagenase, protease, nuclease, lipase, etc) * **protect the pathogen** by interfering with normal host defense mechanisms such as clotting (ex. coagulase)

Question 44

Toxic or destructive substances produced by the pathogen that directly or indirectly enhance invasiveness and host damage by facilitating and promoting infection.

Answer 44

Virulence factors

Question 45

Highly virulent pathogens show _little/large_ difference in the number of cells required to kill 100% of the population as compared to 50% of the population.

Answer 45

little

Question 46

Name the pathogen property: Organism produces a toxin that inhibits host cell function or kills host cells.

Answer 46

Toxicity

Question 47

Name the pathogen property: Ability of a pathogen to grow in host tissue at densities that inhibit host function.

Answer 47

Invasiveness

Question 48

Name the pathogen property: Decrease or loss of virulence.

Answer 48

Attenuation

Question 49

\_\_\_\_\_\_\_\_ strains of various pathogens are valuable to clinical medicine because they are often used for the production of viral vaccines.

Answer 49

Attenuated

Question 50

Name four examples of attenuated vaccines.

Answer 50

* measles * mumps * rubella * rabies

Question 51

A virus is _________ in hosts that are increasingly dissimilar to the original host.

Answer 51

attenuated

Question 52

Genes that direct invasion are clustered together on the chromosomes as _____________ .

Answer 52

pathogenicity islands

Question 53

Invasiveness requires a pathogen to break down host tissues. This is often done with _______ that attack host cells.

Answer 53

enzymes

Question 54

Name three tissue destroying enzymes:

Answer 54

* hyaluronidase * coagulase * stretokinase

Question 55

This enzyme breaks down host tissue.

Answer 55

hyaluronidase

Question 56

This enzyme forms clots.

Answer 56

coagulase

Question 57

This enzyme breaks down clots.

Answer 57

streptokinase

Question 58

The function of this exoenzyme is to: Degrade hyaluronic acid that cements cells together to promote spreading through tissues.

Answer 58

Glycohydrolases (Hyaluronidase S in *Staphylococcus aureusI)*

Question 59

The function of this exoenzyme is to: Degrade DNA released by dying cells (bacteria and host cells) that can trap the bacteria, thus promoting spread.

Answer 59

Nucleases | (DNAse produced by *S. aureus*)

Question 60

The function of this exoenzyme is to: Degrade phospholipid bilayer of host cells, causing cellular lysis, and degrade membrane phagosomes to enable escape into the cytoplasm.

Answer 60

Phopholipases | (Phopholipase C of *Bacillus anthracis*)

Question 61

The function of this exoenzyme is to: Degrade collagen in connective tissue to promote spread.

Answer 61

Proteases (Collagenase in *Clostridium perfringens*)

Question 62

Toxic proteins released from the pathogen as it grows.

Answer 62

Exotoxins

Question 63

Three categories of exotoxins.

Answer 63

* cytolytic toxins * AB toxins * superantigen toxins

Question 64

Ability of microorganism to cause disease as a result of preformed toxin that inhibits host function or kills host cells.

Answer 64

Toxicity