structure of bacteria II

Question 1

What are the differences between Prokaryotic and Eukaryotic cells?

Question 2

What is the great divide between bacteria?

Answer 2

The great divide is between

Gram-positive and Gram-negative bacteria

Gram-positive bacteria are monoderm, contain one thick layer of peptidoglycan and contains teichoicand lipoteichoic acid.

Gram-negative bacteria are diderm, contains an outer membrane with lipopolysaccharides.

Question 3

What are the subunits of the 3D peptidoglycan polymer?

Answer 3

Disaccharide N-
acetylglucosamine
N-acetylmuramic acid

Question 4

How are the subunits of peptidoglycan bound?

Answer 4

Via cross-links between the sub-units to form long polymers that are further cross-linked by peptide cross-links

Question 5

How is DNA contained in bacteria?

Answer 5

In nucleoids

Contains highly supercoiled DNA wrapped around proteins

Question 6

What is the shape of nucleoids?

Answer 6

Nucleoids can change shape dramatically

Barely visible during restHighly visible when active

Can change its shape, form and function within the bacterial cytoplasm.

Question 7

What are gas vacuoles?

Answer 7

Bacteria need to be able to contain gas intracellularly

Largest bacteria can fix nitrogen and sulphur via sulphur inclusions1mm in diameter

Question 8

What are microcompartments?

Answer 8

Microcompartments are large, crystalline, structurally sophisticated

100-150 nm in X section

Consist of 10 000 -20 000 polypeptides of 10 to 20 types

Question 9

What is a microcompartment shell?

Answer 9

Encasesmetabolic enzymes that catalyze reaction with toxic intermediate

Unifying structure of the microcompartments

Made of proteins having bacterial compartment domains

Question 10

Examples of microcompartments

Answer 10

Carboxysome - metabolism

PDU compartment- metabolism of alcoholin Salmonella enterica

Question 11

Why is the cytoskeleton important?

Answer 11

Cytoskeleton changes the shape of cells and aids the cell in cellfission

MreB (actin precursor) - elongates the cell to form rod-shaped bacteria

FtsZ - used in peptidoglycan formation

Crescentin- bends the wall to one side

Question 12

Why can’t gram positivebacteria form vesicles?

Answer 12

Their peptidoglycan cell walls are too thick

Question 13

How do vesicles form in gram-negative bacteria?

Answer 13

1. Asymmetric expansion of the outer membrane relative to the inner membrane
2. Ratio of inner to outer membrane buckles
3. Curvature increases and the final outer membrane vesicles form
4. Vesicles trap components in the periplasm

Question 14

What is the periplasm?

Answer 14

Space between the outer and inner layer of the bacteria

Question 15

What is in the most likely molecule to be found in the bacterial vesicles?

Answer 15

DNA

Question 16

Components of the outer layer of bacteria

Answer 16

Short filaments 
S-layer proteins 
Lipoproteins 
Capsules 
Flagella

Question 17

What are bacterial capsules ?

Answer 17

Extended polysaccharide structures that protect the bacteria from immune attack

Question 18

What are filaments?

Answer 18

Adhesins

Question 19

How does the flagellum work?

Answer 19

The rotor turns via an ATP-dependent mechanism that causes the flagella to whip

Question 20

Why are flagella needed?

Answer 20

In order to swim in aqueous environment

hunt down nutrients

Question 21

Can human and bacterial flagella be distinguished?

Answer 21

Yes, via their form and function

Question 22

What are the three types of flagella?

Answer 22

Monotrichous
Peritrichous
Amphitrichous

Question 23

What are monotrichous flagells?

Answer 23

Single

Question 24

What are peritrichous flagella?

Answer 24

Multiple

Question 25

What are amphitrichous flagella?

Answer 25

One on either side of the bacteria

Question 26

What are S-layer proteins?

Answer 26

Proteins that form paracrystalline arrays on the bacterial surface

Question 27

What are the functions of S-layer proteins

Answer 27

Structural - prevent viral infection, help biofilms, protection and inhibit complement 
Receptor interaction 
Peptidoglycan remodelling 
Cell wall integrity 
Selectivity filter 
Inhibition of phagocytosis and serum killing 
Resistance to presentation 
Cell division and cell length 
Iron uptake 
Swimming 
Aggregation and bodies formation

Question 28

What are the targets of toxins in drugs attacking bacteria?

Answer 28

Alteration of cytoskeleton
Inhibition of membrane fusion
Alter membrane permeability
Interfere with cell signalling