Lecture 1: Part 1

Question 1

Bacteria, most common shapes

Answer 1

Rod and cocci

Question 1

Planes of division

Answer 1

of cocci:
1 plane = dipplococco
- Stay together = pair
- Long chain = streptococci

2 planes = tetrads (4 cells)

3 planes = cubical (8cells)

Random planes = staphtloccucs

Question 2

Prokaryotic cell

Answer 2

Cell walls
Capsule
Ribosomes
Fimbrea
Plasma membrane
Nucleoid
Flagelle
Inclusions

Question 3

Cell wall

Answer 3

Cell shape and osmotic stress protection

Question 4

Capsule

Answer 4

Thick polysaccharide layer outside cell wall

Osmotic stress and host immune protection

Question 5

Ribosomes

Answer 5

RNA to proteins

Question 6

Fimbrea

Answer 6

attachement to surfaces

Pili

Question 7

Plasma membrane

Answer 7

Permeable barrier

Location of metabolic processes

Question 8

Nucleoid

Answer 8

Localisation of DNA

Question 9

Flagelle

Answer 9

Cellular movement

Question 10

Inclusions

Answer 10

Storage of C and P and other substances

Question 11

Cell wall:
- Location
- Functions

Answer 11

Ourside plasma membrane

Aids in determining cell shape
Protection osmotic
Protect from toxins
Contributes to pthogenesis for some bacteria

Question 12

Gram + and - bacteria

Answer 12

Gram +:
- 1 membrane
- 1 giant peptigoglycan layer
- 1 small periplasm
Gram -:
- 2 membres
- Thick peiplasm
- 1 thin peptigoglycan layer

Question 13

What is associated with petigoglycane and what is the role of this structure

Answer 13

• Teichoic acid
• Made of glycerol-phosphate
• Assist with cell wall rigidity

Question 14

Periplasm space

Answer 14

• Hydrolytic enzymes and proteins for nutrient processing and uptake

Question 15

peptidoglycane structure

Answer 15

2 sugar derivatives (NAG and NAM)

NAM is linked to L-alanine, glutamic acid, DAP (-) and L-lysine (+) and D-alanine

Question 16

To create a meshlike polymer, peptidoglycane can be cross linked. How does this occur?

Answer 16

1) Gram -:Direct cross-linking between subunits: D-Ala to DAP
2) Gram +: Cross-linking via peptide interbridges: (D-Ala to L-Lys glycine tetrapeptide)

Question 17

The cross-linking in bacteria result in:

Answer 17

A hightly dense interconnected peptidoglycan network

Can vary between different bac species (another way to identify bacteria!)

Question 18

What is on the surface of gram - bacteria

Answer 18

LPS

on external membrane of gram neg bacteria

Question 19

What is LPS:
- made of (a.a)
- Parts
- Roles

Answer 19

Core polysaccaccharrides: Abe, Tha, Gal, Man, FlcN, Hep, KDD

O antigen: Diversity amoung AND within species, O antigen structure can be altered to evade host immune response

Lipid A: SIMILAR in all gram neg bacteria. endotoxin. highly hydrophobic

Adhesion, permeability, evasion of immunity

Question 20

Pili
- Another name
- WHat is it
- Function

Answer 20

Fimbrea

• Thin proteinous fibres on surface of bacterial cells
• Hollowed-cored appendages
• Adherence to surfaces as host epithelial cell, bacteria or innate surfaces
• Type 4: twitching motility
• Conjugaison

Question 21

The Capsule
- What is it
- WHere is it found
- Functions

Answer 21

• Polysaccharide layer that coats cell wall exterior
• gram - and +
• Host phagacytosis protection
• Protects agains dehydration
• Exclude virus or other hydrophobic toxins
• Facilitate adhesion

Question 22

Koch’s Postulates

Answer 22

1) The microorganism must be present on every case of the disease but absent from healthy organism
2) The suspect microorganisms must be isolated and grown in a PURE CULTURE
3) The same disease must result when isolated microorganism is innoculated into a health host
4) The same microorganism must be isolated again from the diseased host

Question 23

Limitations of Kochs postulates

Answer 23

• Asymptomatic carries
• Pure culture difficult in lab
• Ethics humans and animals (some human diseases do not cause disease in animals)

Question 24

THe infectious process

Answer 24

Entry into host Perisistence (adhesion, invasion, persistence) Evasion of host defense Replication Damage to host Dissemination Maintain a reservoir (place where bacteria usually lives)

Question 25

Invasion of bacteria into host cell

Answer 25

Attachement of bacteria to host cell multiple mechanism of bacterial invasion Adhesion and invasion arent always coupled

Question 26

**2 examples of bacterial invasaion of host cell**

Answer 26

1) direct interaction with host receptors - Certain bacteria may express proteins on surface that bind to host cell receptor and intiates actin-dependant phagocytocis 2) Translocation of bacterial proteins - Certain bacteria may inject effector proteins vis SECRETION SYSTEMS into host cell, triggering actin dependant engolfment

Question 27

Pathogen

Answer 27

a disease causing organism

Question 28

Pathogenecity

Answer 28

The ability of an organism to cause disease

Question 29

Virulence

Answer 29

Refers to the degree or measure of pathogenecity

Question 30

Virulence factor

Answer 30

Bacterial products that contributes to virulence

Question 31

THe most common types of virulence factors involve those that contribute to bacterial

Answer 31

- adherence - Invasiveness - Immunoevasion - Toxigenicity

Question 32

Koch's postulates - Molecular perspective

Answer 32

1) The virulence trait under study should be associated much more with pathogenic strains of the species than with nonpathogenic strains 2) Inactivation of gene coding for this virulence trait (mutated) should in fact cause the bacteria to loose pathogenicity 3) Replacement of the mutated gene with the normal WT gene should fully restore pathogenicity 4) THe gene should be expressed at some point during the disease process 5) ANtibodies or immune system cells directed against the gene products should PROTECT the host

Question 33

Where can virulence genes be coded?

Answer 33

- Extrachromosomal plasmids - Pathogenicity island: Large clusters of DNA present within the bacterial chromosome - Bacteriophages or transposons can intergrate genes into bacteria chromosomes

Question 34

Horizontal transfer types

Answer 34

Transformation: F for Free DNA Transduction: Bacteriophage injects Conjugation: extrachromosomal plasmid

Question 35

**Some characteristic features of pathogenicity islands**

Answer 35

- Insertion elements at the 5'-3' ends suggests promiscuity as mobile elements - Express factors that promote mobility - Intergrases, transposases - The GC content of PAIs may differ from the remainder of the bacterial genome - Consists of several open-reading frames - genes that encorde virulence factors - A pathogen may have one or more PAIs - May be found in both gram - and gram + bacteria

Question 36

**Example of a simplified pathogenic mechanism of Enteropathogenic E.coli**

Answer 36

Tyoe III secretion system translocates virulence protein Tir into the host cell Adhesion: - Intimin of bacterial cell surface binds Tir that is displayed on host cell surface Phosphorylation of Tyr promotes signal transduction that causes actin cytoskepeton rearrangement and pedestal formation that pushes the bacteria upwards