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PB > Lecture 1: Part 1 > Flashcards

Lecture 1: Part 1 Flashcards

1
Q

Bacteria, most common shapes

A

Rod and cocci

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1
Q

Planes of division

A

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

2 planes = tetrads (4 cells)

3 planes = cubical (8cells)

Random planes = staphtloccucs

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2
Q

Prokaryotic cell

A

Cell walls
Capsule
Ribosomes
Fimbrea
Plasma membrane
Nucleoid
Flagelle
Inclusions

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3
Q

Cell wall

A

Cell shape and osmotic stress protection

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4
Q

Capsule

A

Thick polysaccharide layer outside cell wall

Osmotic stress and host immune protection

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5
Q

Ribosomes

A

RNA to proteins

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6
Q

Fimbrea

A

attachement to surfaces

Pili

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7
Q

Plasma membrane

A

Permeable barrier

Location of metabolic processes

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8
Q

Nucleoid

A

Localisation of DNA

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9
Q

Flagelle

A

Cellular movement

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10
Q

Inclusions

A

Storage of C and P and other substances

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11
Q

Cell wall:
- Location
- Functions

A

Ourside plasma membrane

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

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12
Q

Gram + and - bacteria

A

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

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13
Q

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

A
  • Teichoic acid
  • Made of glycerol-phosphate
  • Assist with cell wall rigidity
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14
Q

Periplasm space

A
  • Hydrolytic enzymes and proteins for nutrient processing and uptake
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15
Q

peptidoglycane structure

A

2 sugar derivatives (NAG and NAM)

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

16
Q

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

A

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)

17
Q

The cross-linking in bacteria result in:

A

A hightly dense interconnected peptidoglycan network

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

18
Q

What is on the surface of gram - bacteria

A

LPS

on external membrane of gram neg bacteria

19
Q

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

A

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

20
Q

Pili
- Another name
- WHat is it
- Function

A

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
21
Q

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

A
  • Polysaccharide layer that coats cell wall exterior
  • gram - and +
  • Host phagacytosis protection
  • Protects agains dehydration
  • Exclude virus or other hydrophobic toxins
  • Facilitate adhesion
22
Q

Koch’s Postulates

A

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

23
Q

Limitations of Kochs postulates

A
  • Asymptomatic carries
  • Pure culture difficult in lab
  • Ethics humans and animals (some human diseases do not cause disease in animals)
24
Q

THe infectious process

A

Entry into host

Perisistence (adhesion, invasion, persistence)

Evasion of host defense

Replication

Damage to host

Dissemination

Maintain a reservoir (place where bacteria usually lives)

25
Q

Invasion of bacteria into host cell

A

Attachement of bacteria to host cell

multiple mechanism of bacterial invasion

Adhesion and invasion arent always coupled

26
Q

2 examples of bacterial invasaion of host cell

A

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

27
Q

Pathogen

A

a disease causing organism

28
Q

Pathogenecity

A

The ability of an organism to cause disease

29
Q

Virulence

A

Refers to the degree or measure of pathogenecity

30
Q

Virulence factor

A

Bacterial products that contributes to virulence

31
Q

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

A
  • adherence
  • Invasiveness
  • Immunoevasion
  • Toxigenicity
32
Q

Koch’s postulates - Molecular perspective

A

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

33
Q

Where can virulence genes be coded?

A
  • Extrachromosomal plasmids
  • Pathogenicity island: Large clusters of DNA present within the bacterial chromosome
  • Bacteriophages or transposons can intergrate genes into bacteria chromosomes
34
Q

Horizontal transfer types

A

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

35
Q

Some characteristic features of pathogenicity islands

A
  • 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
36
Q

Example of a simplified pathogenic mechanism of Enteropathogenic E.coli

A

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

PB (9 decks)

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