Lecture 3 - Structure and function of bacteria

Question 1

What is the capsule composed of and how can it be protected

Answer 1

Polysaccharides or polypeptide (called slime layer or glycocalix) which is a sticky layer of goo on outside.

It can prevent desiccation and prevent phagocytosis as the slime capsule can hide the bacteria from the immune system a bit more

Question 2

What does plaque (e.g.streptococcus mutans) stick to teeth

Answer 2

The sticky capsule

Question 3

Describe a biofilm

Answer 3

Community of microorganisms stuck together in a goo so they stick to a surface. They function as a unit.

Question 4

Describe issues with bio films

Answer 4

Hard to control, more resistant to cleaning and antibiotics.

Question 5

Name and describe the 4 types of flagella

Answer 5

Monotrichous - single polar flagellum
Lophotrichous - two or more at one/both ends
Amphitrichous - single polar flagellum at each end
Peritrichous- disturbed over entire cell

Question 6

Describe a typical prokaryotic cell

Answer 6

Cytoplasm, nucleoid, ribosomes, cytoplasmic membrane, cell wall, capsule, flagella

Question 7

In gram negative or gram positive bacteria does the flagellum spin anti-clockwise to move forward?

Answer 7

Gram negative

Question 8

What are the 3 rings called in the flagellum that penetrate the cell wall (from lipid layer to inner membrane)

Answer 8

L (lipid)
P (peptidoglycan)
M (membrane -inner)

Question 9

Which way would gram negative bacteria spin their flagellum to move backwards

Answer 9

Clockwise

Question 10

What is the process called of a bacterial cell undergoing motility and describe the process

Answer 10

Run and tumble.
Run - moving forward towards with bundled flagella
Tumble - flagella pushed apart from clockwise rotation until aware of direction to travel
Run again in direction

Question 11

What are the two types of Chemotaxis and describe the

Answer 11

Positive Chemotaxis - movement towards a molecule

Negative - movement away from a molecule

Question 12

What is the difference between fimbrae and pili

Answer 12

Fimbrae - early attachment structure, have hooks so organisms moved through the body with food use fimbrae to grapple on side of gut

Pili- join 2 cells together. Bacteria can undergo a form of sexual recombination of genome through pilus (whereas normally clone) give to DNA to another cell

Question 13

How many fimbrae are there compared to pili

Answer 13

Fimbrae many fibres whereas pili one to two per cell

Question 14

What protein is pili made of

Answer 14

Pillin

Question 15

List two functions of the cell wall in gram negative and positive bacteria

Answer 15

Prevent osmotic rupture and contributes to disease mechanisms

Question 16

What are the repeating subunits that form peptidoglycan

Answer 16

NAG - N-acetylglucosamine

NAM - N-acetylmuramic acid

Question 17

What does the outer membrane of the gram negative bacteria have

Answer 17

Lipopolysaccharide sticking up - endotoxins which trigger the immune system to give certain presentations of gram negatives infection. Also has a porin protein

Question 18

What is the LPS made of

Answer 18

LIPID A and O polysaccharide

Question 19

How much of bacterial cells are water

Answer 19

70%

Question 20

What is the internal matrix of the cell (cytoplasm) composed of and what other things are contained within the cytoplasm

Answer 20

80% H2O
Proteins, COH, lipids

Other things - inclusion bodies (store things), DNA, ribosomes

Question 21

How is the genome split in bacteria

Answer 21

Chromosomes and plasmid (replicate independently of genome) which is transferable.

Question 22

What is conjugation?

Answer 22

Pilus is link where copied plasmid can go through so both cells have plasmid

Question 23

What is transformation?

Answer 23

Transfer genetic info without the bacterial cell being in the environment. When cells die they tend to lyse - bacterial cells take up DNA when naked DNA bind to cell wall and taken up by bacteria.

Question 24

What is transduction

Answer 24

VIRUSES Take DNA from one cell and put it in another.

Question 25

What is horizontal gene transfer

Answer 25

Bacterial genome influenced by environment leads to changes e,g. Plasmid and genetic lineage taken up by surrounding cells e.g. Lecturer give us info

Question 26

What is vertical Lineage

Answer 26

Bacterial cells give info to offspring e,g, lecturer give info to his children

Question 27

What is the total S for the ribosomes in prokaryotes and eukaryotes

Answer 27

70s prokaryotes | 80s eukaryotes

Question 28

What antibiotics target ribosomes

Answer 28

Streptomycin Neomycin Tetracyclines

Question 29

Name the inclusion body that stores phosphates if there is a loss of them

Answer 29

Volutin

Question 30

On what type of bacteria do endospores occur and give examples

Answer 30

Gram positive | Clostridium and bacillus

Question 31

At what 4 positions can the endospore form

Answer 31

Terminally (at one end) Sub terminally (near one end) Centrally Size (same size as cell so doesn't make it swell)

Question 32

Is sporulation a replicative process

Answer 32

No the cell undergoes sporulation to protect the cell from a harsh environment 1 cell = 1 endospore

Question 33

Describe the process of sporulation

Answer 33

1- Take a big bit of genome and move it to one Side of cell 2- begin to grow membrane around it so forms a forespore 3- start to protect it layer it in coats of peptidoglycan so if environment gets harsh then it is protected. 4- when environment gets better the cell starts to grow out and it's called germination. 5- water gets into cell so spore swims away

Question 34

Describe the process of germination

Answer 34

``` 1- germination 2- swelling 3- shedding of spore wall 4- outgrowth of vegetative cell 5- cell division ```

Question 35

Compare exotoxins and endotoxins

Answer 35

Exotoxins - gram + bacteria, produced inside bacteria as part of growth and released from cell Endotoxins - part of gram - cell wall.

Question 36

Describe the structure of exotoxins and their features

Answer 36

Protein molecules - have active (a group) subunit and binding (b group) subunit so SPECIFIC MAINLY GRAM + - soluble in blood - rapid transmission - rapid onset of symptoms

Question 37

Give two examples of exotoxin producers

Answer 37

Clostridium botulinum - inhibits release of acetylcholine (toxin bind to other side, muscle flaccid and paralysis) Clostridium tetani - inhibits removal of acetylcholine (spasmic paralysis, tetanus toxin blocks other side, fits and spasms and die)

Question 38

Describe the structure of endotoxins and their features

Answer 38

Outer cell wall of gram -. Lipid portion of LPS - lipid A Released on cell lysis Symptoms, same regardless of species - severity can vary - fever, weakness, general aches, shock. Cause immune system to go into panic General