Infectious Disease, Microbiology, Bacterial Genetics

Question 1

Transmission: spread by contact with the agent on the infected host or from saliva, discharges on the skin, feces, urine, respiratory or genital secretions

Answer 1

direct transmission

Question 2

organism shed by host into water, milk, food, air, bedding, dust, equipment; contact with contaminated inanimate objects

Answer 2

indirect transmission

Question 3

Sources of infectious agents

Answer 3

normal microbiota
infected and diseased host
soil. water, fomites

Question 4

Parts of infectious disease triangle

Answer 4

Host, Environment, Organism

Question 5

3 main parts of the bacterial cell envelope

Answer 5

Cell wall, periplasm, inner membrane

Question 6

Characteristics of bacterial inner membrane

Answer 6

lipid bilayer
uptake systems
export systems
electron transport
permeability barrier

Question 7

Characteristics of bacterial periplasm

Answer 7

viscous, oxidizing environment
contains enzymes catalyzing formation of disulfide bonds
contains proteins participating in small molecule break down of polymers to bite size compounds

Question 8

Characteristics of bacterial cell wall

Answer 8

peptidoglycan

counters osmotic pressure

Question 9

What bond links NAG and NAM in the bacterial cell wall

Answer 9

B (1,4) glycosidic bonds (pentapeptide linked to NAM)

Question 10

Main difference between cell wall of gram positive and negative bacteria

Answer 10

Negative - thin (and has extra outer membrane)

Positive - thick

Question 11

What colors do gram positive and negative bacteria stain?

Answer 11

Negative - pink

Positive - purple

Question 12

Describe the outer and inner leaflets of the outer membrane of gram negative bacteria

Answer 12

Outer leaflet of outer membrane = Lipopolysaccharides

Inner leaflet = phospholipids

Question 13

What are the 3 components of LPS?

Answer 13

O-antigen
Core
Lipid A

Question 14

most abundant molecule on the surface of gram neg bacteria

Answer 14

LPS

Question 15

what is the toxic region of LPS

Answer 15

Lipid A

Question 16

What is the purpose of a bacterial capsule

Answer 16

protection, immune evasion

Question 17

what is the shape of the bacterial genome

Answer 17

double stranded DNA, helical, supercoiled, forms a circle

Question 18

the bacterial genome is (haploid/diploid)

Answer 18

haploid

Question 19

circular DNA molecules capable of autonomous replication

Answer 19

plasmids

Question 20

In bacteria, DNA replication in (unidirectional/bidirectional) from a single origin of replicaiton

Answer 20

bidirectional

Question 21

Operon

Answer 21

have the same promoter, all genes transcribed as one block (ex. one promotor, one transcriptional start site, 3 open reading frames, 3 proteins produced from one mRNA)

Question 22

regulon

Answer 22

promoter binds the same regulatory factors which allow genes to be expressed at the same time and/or under the same conditions even though they are not physically close to one another on the genome

Question 23

Translation is initiated by the binding of the (30S/50S) subunit to the ribosome binding site on the mRNA

Answer 23

30S

Question 24

3 sites of the 50S subunit

Answer 24

A (acceptor)
P (peptide)
E (exit)

Question 25

4 ways bacteria acquire new DNA material

Answer 25

Natural transformation (uptake of naked DNA) Conjugation (transfer of plasmid DNA from one bacterium to another) Transduction (infection by bacteriophage) Acquire genes that specify antibiotic resistance genes, genes encoding virulence factors (e.g. toxins)

Question 26

To cause disease a bacteria must

Answer 26

Interact with host surfaces Avoid clearance by the host Acquire nutrients to grow

Question 27

What are 3 ways bacteria interact with host surfaces

Answer 27

adherence biofilms invasion

Question 28

2 requirements for adhesion

Answer 28

``` adhesin (binding entity on bacterium) cognate receptor (binding molecule on host surface) ```

Question 29

obstacle to adhesion

Answer 29

both surfaces negatively charged

Question 30

3 major types of adhesin-receptor interactions

Answer 30

Lectin-carbohydrate (bacterial adhesin is the lectin in most cases) Protein-protein (fibronectin, integrins) Hydrophobin-lipid (hydrophobic region of protein adhesin interacts with lipids)

Question 31

major types of bacterial adhesin (initial)

Answer 31

pilus | fibrillar surface proteins

Question 32

major type of bacterial adhesin (intimate)

Answer 32

integral membrane adhesin

Question 33

communities of microorganisms encased within an extracellular polymeric matrix and living on a surface

Answer 33

biofilm

Question 34

rational for biofilms ability to protect against toxic environment

Answer 34

bacteria on periphery are killed, cells in the middle are protected

Question 35

ability to gain entry inside host cells, allows bacteria to cross physical barriers, hide from the immune system, disseminated from the site of infection

Answer 35

invasion

Question 36

general strategy for invasion and the two main mechanisms

Answer 36

General strategy: rearrangement of actin cytoskeleton | Mechanisms: zipper, trigger

Question 37

Invasion - zipper mechanism

Answer 37

activation of membrane-located host cell receptors by invasion factor(s) on surface of bacteria - receptors are ALREADY present on surface of host cells

Question 38

__________ and accumulation of more receptors lead to engulfment of bacteria by zipper-like mechanism

Answer 38

invagination

Question 39

invasion - trigger machanism

Answer 39

requires injection of bacterial proteins into the cytoplasm of host cell

Question 40

Type Three Secretion System (TTSS)

Answer 40

common and well-characterized injectisome system

Question 41

in TTSS trigger mechanism, bacterial effectors subvert eukaryotic signaling pathways, rearranging actin to form _________ that will engulf bacteria

Answer 41

pseudopods

Question 42

Main ways bacteria avoid clearance by the host

Answer 42

Antigenic variation (changing antigens and epitopes) Phase variation (turn-off production of a protein) slgA protease (prevents trapping of bacteria in mucus bathing mucosal surfaces) Capsule Interference with complement cascade (C5a peptidase)

Question 43

2 ways bacteria can survive in host cell

Answer 43

Cytosolic and Intravacuolar (in both, protected from antimicrobial content of lysosome)

Question 44

Characteristics of a bacterial capsule (4)

Answer 44

Antiphagocytic Host mimicry Sheild (stealth mode) Prevents activation of complement cascade

Question 45

Why is acquiring iron an issue for bacteria?

Answer 45

It is one of the most abundant elements in nature BUT... it is insoluble under physiologic conditions and sequestered in animal hosts

Question 46

Bacterial solutions for acquiring iron

Answer 46

Receptors for host iron binding proteins | Siderophores (high affinity for iron)