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From cells to organisms > lectures 1-6 > Flashcards

lectures 1-6 Flashcards

bacteria world

1
Q

what is the importance of studying bacteria?

A

antimicrobial resistance 10 m deaths by 2050

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2
Q

where are bacteria found?

A

Plants
Animals
Soil
Water
Air
Arctic Ice
Volcanic vents-
huge diversity

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3
Q

what is the capsule for?

A

protection

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4
Q

what is the cell wall for?

A

structure

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5
Q

pilus

A

attachment

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6
Q

flagella

A

movement

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7
Q

features of bacteria

A

No mitochondria – functions performed by cytoplasmic
membrane
* Ribosomes (70S - 30S and 50S subunits) free in the
cytoplasm or bound to inner face of cytoplasmic membrane
– no ER
* Single chromosome (nucleoid) – no nuclear membrane

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8
Q

where does transcription and translation occur?

A

cytosol

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9
Q

gram positive have

A

thick wall of peptidoglycan

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10
Q

what is peptidoglycan for?

A

binary fission, die slowly without.

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11
Q

what are l form bacteria?

A

L-forms are bacterial variants that lack a cell wall and divide by a variety of processes involving membrane blebbing, tubulation, budding resistance to antibiotics

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12
Q

why is cell wall important?

A
  1. It is essential for viability
  2. It is one of the most important sites for attack by antibiotics
  3. It provides ligands for adherence and receptor sites for drugs
    or viruses
  4. It is a ”microbial associated molecular pattern” that is recognised by
    host recognition proteins – activates host signalling cascades
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13
Q

peptidoglycan made of what?

A

Glycan chains connected by peptide crosslinks,B-1,4 glycosidic linkages

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14
Q

what are the residues?

A

N-acetyl muramic acid N-acetyl glucosamine

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15
Q

d- alanine dimers do what

A

direct cross link to L-diaminopimelic acid (free amino group)

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16
Q

what is lost during cross linking

A

5th amino acid lost during
cross-linking!

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17
Q

diversity of bacteria

A

in population of bacteria each cell is unique mutant variety’s

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18
Q

cell envelope

A

Elements of the cell envelope that help bacteria
adhere to surfaces, escape the immune system
& cause disease

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19
Q

Gram-negative cell envelope

A

Inner membrane:
Phospholipid on
inner and outer face
Outer membrane:
* Phospholipid inner face
* LPS outer face

20
Q

what is lps

A

Lipopolysaccharides (LPS)

21
Q

what does lps do ?

A

1.LPS is a barrier against hydrophobic agents, detergents, bile,
antibiotics
2. Forms a very tightly packed layer – strong lateral interactions
between LPS molecules
3. Proinflammatory – Interacts with receptors on macrophages and Bcells leading to cytokine release – can cause endotoxic shock.

22
Q

TLR4 ligand

A

Binds to TLR4 and triggers
upregulation of pro-inflammatory cytokines.
This can cause entotoxic shock.

23
Q

how many forms of lps

A

3 forms of lps

24
Q

what are the 3 forms of lps

A

rough smooth and lipid a

25
rough lps has
poor adherence to host cells
26
Because rough lps has shit adherence why would they lose the o- antigen that makes it smooth?
O-antigen targeted by antibiotics, host immune cells, antimicrobial peptides and bacteriophages Loss of O-antigen allows bacteria to “hide” from host Modification of LPS also possible
27
Vibrio cholerae what happens when its modified o antigen?
lipid a is modified Host antimicrobial peptides (CAMP’S) recognise lipid A Amino-acid (glycine) modification of lipid A
28
gram positive cell envelope
1. Teichoic acids 2. Cell wall anchored proteins (covalently bound)
29
what are tectonic acids?
Teichoic acids are negatively charged polymers
30
Role of Teichoic Acids
Binding to receptors and surfaces Negative surface charge Protection from harmful molecules antibiotics Cation homeostasis Growth and division
31
Modifications of Teichoic acids
d-Alanine – increased resistance to host defenses, antimicrobial peptides, glycopeptide antibiotics Glycosylation – increased protection from immune system
32
Modifications are not always beneficial
Glycosylation may increase susceptibility to bacteriophages D-alanine modifications can reduce ability to adhere to host cells and establish an infection
33
what is for attachment of bacteria gram positive?
Cell wall anchored proteins are synthesised in the cytoplasm * They are translocated across the cytoplasmic membrane (secretion) * They become covalently anchored to peptidoglycan and displayed on the bacterial surface * Key role in attachment / adhesion
34
sortase enzymes do what?
In Gram-positive bacteria proteins are displayed on the cell surface using sortase enzymes.
35
Capsules, EPS and biofilms – what do they have in common?
Outermost layer of protection * Common structure, biogenesis and export pathways * Assist in adhesion to solid surfaces * Protect against antibiotics, antimicrobial peptides and host immune responses * Make infections hard to treat
36
what are capsules?
a biofilm for one. Capsule is a type of glycocalyx (sticky sugar coat) Distinct, gelatinous = Capsule * High water content * Important for virulence – resists phagocytosis
37
opsonins
Opsonins directed to cell envelope components are deposited beneath the capsular layer. opsin reseptors triger phagocytosis.Capsule inhibits access to opsonins
38
Serotype =
grouping bacteria based on cell envelope surface structures
39
Extracellular polysaccharides (EPS) what are they
EPS form the biofilm matrix. for eample the three types 1.Soft, loose polymer 2.Fabric-like matrix3. Tight scaffold
40
biofilms are
* Impervious to phagocytosis by neutrophils and macrophages * Resistant to antimicrobial peptides and complement * Semi-dormant - difficult to inhibit with antibiotics
41
the s layers are what
chainmail- Extracellular layer coating the entire bacterial cell surface
42
s layer
Composed of protein or glycoprotein
43
Functions of S-layer
Molecular sieve Cut-off determined by size and morphology of pores * Protection Resistance to bacteriophage, complement, phagocytosis, extreme environments * Adhesion to host cells Scaffold for adhesion proteins
44
Fimbriae
Help attach cells to a solid surface or tissues * Help bacteria cling together
45
pili
Longer, fewer and thicker tubes (1-2 per cell) * Made of Pilin protein * Sex pili (conjugation) and ordinary pili * Attach to other bacteria * Motility (crawling/twitching) * Mostly Gram negative
46

From cells to organisms (18 decks)

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