3. Bacterial Structure and Function

Question 1

Prokaryotes have no internal/external membranes, single/double chromosomes, no/some histones and no … of gametes

Answer 1

• internal
• single/haploid
• no
• fusion

Question 2

Bacteria are found everywhere but concentrate at where?

Answer 2

interfaces

Question 3

Proteins in bacteria are produced where?

Answer 3

cytosol

Question 4

Bacterial cell length varies from … to …

Answer 4

0.2-700 micrometres

Question 5

There is lots/little communication between outside and inside bacteria

Answer 5

little

Question 6

Role of the Gram Stain

Answer 6

• distinguishes between major groups of bacteria
• based on presence of outer membrane in gram negative bacteria
• was the primary identification until more sophisticated methods were available

Question 7

Difference in cell wall of gram pos and neg - link to gram stain

Answer 7

• pos has thick cell wall of mainly peptidoglycan (retains the crystal violet-iodide complex)
• neg is thinner peptidoglycan and permeable to complex
• neg also has LPS on outer membrane to evade immune response and aid toxicity (o-polysacc varies so immune system can’t detect)

Question 8

How does penicllin target bacteria?

Answer 8

• acts on peptidoglycan
• bursts cell open

Question 9

In gram staining, cells are differentiated by colour. What about in Acid-Fast staining and spore staining?

Answer 9

• acid fast is identified with blue and green differences
• spore means cells are red and spores are green to contrast

Question 10

How does acid fast staining work?

Answer 10

• bacteria with waxy cell walls work well
• carbol fuchsin driven into cells as stain in heat
• destain with 3% acid-alcohol
• high lipid/wax content content means immune response is evaded and requires lots of drugs to target deep in lungs
  e.g mycobacterium tuberculosis (TB)

Question 11

Explain streptococcus pyogenes

Answer 11

• bacteria carried in 5-15% of humans respiratory tract
• acute infections like pharyngitis caused and spread by saliva or nasal secretions
• has a 2-4 day incubation for tonsilitis, fever, headache, lymph node enlargement

Question 12

The bacterial cytoplasmic membrane is a … …, which is a … barrier … nm

Answer 12

• phospholipid bilayer
• thin
• 6-8

Question 13

Bacterial LPS can dissociate from bacteria and impacts dentistry how?

Answer 13

• get into water lines
• can colonise here and spread across patients

Question 14

Bacterial nucleoid is what?

Answer 14

• single chromosome and site of essential genes
• for reproduction and cell division
• defined space in the cell for DNA and not membrane bound

Question 15

Explain plasmids in bacteria

Answer 15

• circular loop of DNA (non-essential genes)
• replicate independently and can be transferred between cells
• allows bacteria to pick up additional info like antibiotic resistance
• closed and seperate from bacterial chromosomes

Question 16

Explain flagella

Answer 16

• enable motility through fluid medium in corkscrew motion like propeller
• moves cell away from less favourable areas
• long and thin to rotate (often longer than cell itself)
• used to classify due to diff patterns
• helical structure
• protein is flagellin subunits

Question 17

Explain peritrichous, polar, lopotrichous flagella

Answer 17

• multiple flagella in diff directions from diff origins of cell
• one flagella
• multiple flagella from the same origin

Question 18

Rotation of the flagella is coupled to …

Answer 18

the flow of protons across the membrane (proton motive force)

Question 19

Explain runs and tumbles of bacterial cell

Answer 19

• chemotaxis in bacteria directed by flagella
• runs happen straight towards the good conditions
• intestinal bacteria rely on this to navigate the intestinal wall
• tumbles occur when the flagella rotate clockwise and becomes less coordinated
• flagella unbundle, allow cell to spin and change direction randomly
• after either, the cell can reevaluate and run/tumble again

Question 20

Explain bacterial fimbriae

Answer 20

• protein filamentous structures
• enable cells to stick to surfaces
• aid biofilm production

Question 21

Explain bacterial pili

Answer 21

• longer version of fimbriae and less of them
• made of protein to attach but more specialised in pathways
• for adhesion of pathogen to host cells
• allow genetic exchange/conjugation and transfer DNA from donor to recipient
• type IV pili has twitching motility to fire out and connect to external environment and pull cell along

Question 22

Explain bacterial capsule

Answer 22

• sticky layer of polysaccharide or protein to help with cell adhesion
• no structural strength but is a tight matrix to adhere to cell wall
• slime layer allows easier deformity but buffers against drying out
• extracellular layer between cell and env

Question 23

Capsule can be stained with what?

Answer 23

india Ink

Question 24

What is the capsule also called?

Answer 24

glycolalyx

Question 25

Function of capsule/glycocalyx

Answer 25

- aid adherance/biofilm - evade phagocytosis - protect against desiccation

Question 26

Explain cell inclusions

Answer 26

- packets of energy reserves or building blocks - safe way to store under osmotic stress - carbon storage polymers (poly-Beta-hydroxybutyric acid/lipid and glycogen) - phosphate and sulphur (dynamic and useful reserve)

Question 27

Explain endospores

Answer 27

- only in highly differentiated cells - resistant but killed by autoclave - C.Diff a good example as causes infection in hospital (spores on hospital beds and instruments so hard to eradicate)

Question 28

Endospores are resistant to ...

Answer 28

- dessication - heat - alcohol - changes in new environment

Question 29

How is spores being highly resistant a good thing?

Answer 29

- spores can be made and then germinate in more favourable conditions - resistant to the bad conditions and then germinate in better ones

Question 30

Spores are difficult to eradicate from what?

Answer 30

- contaminated medical material - food products