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Introductory Microbiology > Structure and Function of prokaryotes > Flashcards

Structure and Function of prokaryotes Flashcards

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Biology 101 flashcards
1
Q

Three main shapes of bacteria

A

COCCUS- close to a perfect sphere
ROD shape - a very short( almost like a sphere) or very long ( bacillus)
SPIRILLIUM- a rod that has a gentle twist on it, a small length with a little twist or SPIROCHETE ( long with a more extreme twist ) -

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2
Q

What is the form of budding and appendaged bacteria

A

Very strange bacteria that has two forms on it-> stalk and budding cells at the same time
Stalk cells - swim
Budding cells- divide

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3
Q

Shape mostly depends on

A

The cell wall

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4
Q

What is the exception fro the rule that all cells have only one genome

A

Filamentous bacteria, because the cell divide , but the cell wall does not separate, forming one cell with multiple genome

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5
Q

What is the role of the cell wall

A

To withstand the intracellular osmotic pressure and is responsible for the shape and rigidity of the bacteria

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6
Q

Explain the procedure of the gram staining

A

We start off with two different types of bacteria
We do not know what they are
1) Flood the cells with crystal-violet, the stain that will turn all the bacteria purple
2) Adding of iodone solution, this will link the the crystal-violet together, forming a large molecule
3) To decolorize with alcohol, by adding ethanol, from one of the cells the crystals will b washed off, but not from others. The one that stay purple are grain positive
4) To the other ones we add a counter stain to make them visible-> gram negative

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7
Q

Why shapes of bacteria are usually gram positive and gram negative

A

Coccus-> gram positive-> appear purple

Rods->negative-> appear any other color,except purple

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8
Q

The difference in cell wall structure between gram-positive and gram-negative bacteria

A

Ethanol is very dehydrating, and cause petidoglycan contract and become even more dense and trap the pigment - the crystals

In the negative they do not have a thick layer peptidoglycan and the pigment washes away. the bacteria has a thin layer of petidoglycan above cytoplasmic membrane and then one more layer- outer membrane

Gram positive have a thick petidoglycan layer above the cytoplasmic membrane

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9
Q

What is the other name for peptidoglycan

A

Murein

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10
Q

2 sugars in peptidoglycan

A

N-acetylglucosamine(NAG)

N-acetylmuramic acid( NAM)

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11
Q

NAG and NAM in peptidoglycan are connected by

A

Beta 1,4 linkage

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12
Q

Subunits of petidoglycan

A

NAG and NAM

Short peptide side chain hanging from NAM

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13
Q

What is particular about peptidoglycan in bacteria

A

1) It has D- amino acids, which is usually not found in living organisms
2) NAM and DAP ( diaminopimelic acid) has never been found in Archea and Eukarya

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14
Q

What is the sequence of polymeric sugar backbone

A

NAG-NAM-NAG-NAM

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15
Q

How does lysozyme function

A

It damages the B bond between the sugars -> damage to petidoglycan layer->protection against bacterial pathogens

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16
Q

Where is lysozyme excreted?

A

In tears, saliva and other body fluids

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17
Q

How does peptidoglycan provide rigidity

A

Polymerization of the sugar backbone-> strength in X direction
The cross-linkage between AA-> rigidity in Y direction

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18
Q

What is the difference in connection between AA in peptidoglycan in Gram positive and gram negative bacteria

A

Gram negative, one AA will directly link with another AA

In gram positive, the connection is made through a connection( interbridge-repeting units of glycine)

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19
Q

How is cross-linking between AA called

A

Transpeptidation

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20
Q

How much percent of the cell wall is peptidoglycan in the wall of gram positive bacteria

A

Up to 90%

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21
Q

In gram -positive bacteria Peptidoglycan has

A 
Wall-associated proteins
Teichoic acid(TA)
Lipoteichoic acid (LTA)
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22
Q

How are wall-associated proteins attached to the peptidoglycan layer?

A

Covalently attached to the peptidoglycan by an enzyme called sortase

23
Q

The composition of TA/LTA

A

Glycerol-phosphate (3C) OR ribitol-phosphate (5C), decorated with AA and sugars

24
Q

TA/LTA are ____ bonded to the peptidoglycan

A

covalently

25
Q

What is the charge of the surface in gram positive bacteria

A

Negatively charged, because of the presence of negative charges on the phosphate groups

26
Q

Structure of LTA

A

from 2 carbons- long, non-polar, hydrophobic FA that are connected to each other with the ester linkage
From the third one a long chain of repeated units of phosphate and carbon

27
Q

How does LTA connected to cytoplasmic membrane

A

LPA extends all the way through peptidoglycan and has FA on the bottom, to allow to imbed in the cytoplasmic membrane

28
Q

Surface proteins of gram negative bacteria should have

A

Hydrophobic domain to allow the anchoring in the outer membrane

29
Q

The outer membrane is decorated with ____

A

Lipopolysaccharides

30
Q

What percentage of the cell wall is peptidoglycan in gram-negative bacteria

A

5-10%

31
Q

What is the cell wall in gram-negative bacteria

A

Periplasm, peptidoglycan, outer membrane

32
Q

What is the function of periplasm

A

The periplasm contains a high concentration of proteins involved in nutrient acquisition, extracellular enzymatic reactions, sensing, etc.

33
Q

What is the other name for periplasm and why

A

It is so dense that it is sometimes called a protein gel

34
Q

What is the other name for outer membrane

A

LPS layer

35
Q

The function of LPS layer

A

Helps to protect the bacteria against a variety of substances, including antibiotics, and against the host defense system

36
Q

The structure of LPS in gram negative bacteria

A

Lipid A, that consists of 6 FA ,which is in the membrane, and N-acetylglucosamine +phosphate
KDO(2-keto-deoxyoctonate) that connects Lipid A to the core polysaccharide
Core polysaccharides and O-specific polysaccharides

37
Q

What is the antigen in LPS layer

A

O-specific polysaccharide that consists of repeating sequence of 2-4 monosaccharides, the way to recognize different strains in one species

38
Q

What is the danger of Lipid A

A

Toxic to many animals. Can result in inflammation and vascular problems(septic shock) that can result in death. Plays the major role in parthenogenesis of Gram-negative bacterial pathogens

39
Q

What is the difference between Archea’s cell wall and bacterial cell wall

A

Archea does not have peptidoglycan and no outer-membrane

40
Q

Cell walls of Archea usually consist of

A

polysaccharides, and/or/ glycoproteins

41
Q

What do Archea have instead of peptidoglycan

A

Pseudopeptidoglycan or pseudomyelin

42
Q

What does Pseudopeptidoglycan have

A

It contains of NAG and N-acetylalosaminuronic acid instead of NAM and has only L-AA

43
Q

Why archea are insensitive to lysozyme

A

The linkage between two sugars in the backbone is beta 1,3 linkage that the lysozyme cannot break

44
Q

Some species of Archea have cell walls that are composed of ___

A

Heteropolysaccharides

45
Q

The great majority of cell walls in Archea species consists of ____ and\or

A

proteins and glycoproteins

46
Q

What is the other name for the cell wall in Archeal species

A

Paracrystalline surface or S-layers

47
Q

Is the S layer is specific only to archea?

A

No, you can find them in some species of bacteria.
Then S-layer will form an additional layer on top of peptidoglycan (Gram-positive) or on the top of the outer membrane ( Gram-negative)

48
Q

What is the difference between capsule and slime layer?

A

Capsules are more firmly attached, slime is more diffused

49
Q

The composition of capsule layer

A

In bacteria- heteroplysaccharides

In some gram-negative bacteria - homopolysaccharides

50
Q

How the capsule is attached in bacteria

A

Covalently bound to the outer membrane or to the peptidoglycan

51
Q

Why the capsule is important virulence determinant?

A

The capsule protects against host defense system

52
Q

What other two surface appendages that batceria and archea can have on the surface?

A

Flagella and fimbriae

53
Q

What is the difference between flagella and fimbriae

A

Flagella are used for locomotion, they are longer (15-20 micrometers)
Fimbriae are primary involved in surface attachement, they are short (less than 4 micrometers)
Fimbria are assembled from the base, flagella-from the top

54
Q

The outer part of flagella consist of

A

The protein- flagellin

Introductory Microbiology (21 decks)

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