11.1 Structure and Classification of Bacteria

Question 1

Do prokaryotes or eukaryotes have a cell wall?

Answer 1

Prokaryotes

Question 2

List the two kinds of acellular microbes

Answer 2

• Bacteriophage
• Virus

Question 3

What do the subgroupings of bacteria naming suggest?

Answer 3

• Point mutations (could alter binding of antibiotics/targets of bacteria)
• Horizontal transfer (from other bacteria)

Question 4

What are some positives of bacteria in society?

Answer 4

• Nutrient Cycling
• Biotechnology (ethanol, genetic manipulation, food supplements)

Question 5

What are some negatives of bacteria to society?

Answer 5

• Spoiling food (pork roast)
• Pathogens (disease for plants and animals, bioterrorism)

Question 6

Why can bacteria be harmful in the case of viral infection? Give an example of this

Answer 6

• Can come on as a secondary infection to a viral infection
• e.g. Bacterial pneumonia following influenza infection

Question 7

What are morbidity and mortality? Are they typically over-reported or under-reported?

Answer 7

Morbidity: Disease
Mortality: Death
Typically under-reported, especially morbidity, since people may not tell health professionals about illness.

Question 8

Give one example of direct damage from bacterial infection

Answer 8

Bacteremia (bacteria in blood)

Question 9

Give two examples of indirect damage from bacterial infection

Answer 9

• Gastric cancer
• Crohn’s Disease

Question 10

Are infectious diseases more of an issue in low income or high income countries?

Answer 10

Low income (less resources: antibiotics, hygiene etc.)

Question 11

Where is the site of gene expression and metabolic activity in bacteria? Why?

Answer 11

• Located in cytoplasm
• Genome is located in cytoplasm; no discrete organelles

Question 12

Describe the chromosome of a bacterial cell, including length

Answer 12

• Single, circular, double-stranded DNA molecule
• <1Mb to ~8Mb

Question 13

Describe the plasmid(s) of a bacteria cell, including length

Answer 13

• Circular DNA molecules
• Vary in size (~2-200kb)
• Vary in number (1-30+)

Question 14

Describe the relationship between a bacteria’s genome size and its requirements for growth

Answer 14

Bigger genome -> less fastidious requirements

Question 15

Describe three methods of DNA exchange in bacteria

Answer 15

• Conjugation (given a copy of a plasmid)
• Transformation (uptake of “free” DNA)
• Transduction (transfer by bacteriophage)

Question 16

What are endospores? How are they formed?

Answer 16

• Complex intracelluar structures, containing DNA protected by many layers of protein
• They are formed when certain strains of bacteria replicated under high temperature, low water content, excessive radiation etc.

Question 17

Why are endospores important clinically?

Answer 17

• Can cause deep tissue infection
• Can express toxins that cause mild-serious disease

Question 18

Where is ATP generated in bacteria?

Answer 18

The cell membrane

Question 19

What is the function of peptidoglycan in cell walls?

Answer 19

• Gives bacteria their shape
• Protects against osmotic pressure

Question 20

What are the cell walls of gram positive bacteria made of? How many layers is it made of, and what kind of gaps does it contain?

Answer 20

Entirely peptidoglycan. Contains up to 100 layers, and contains interbridge gaps in peptidoglycan through which proteins can travel.

Question 21

Is the peptidoglycan layer of gram positive or gram negative bacteria larger?

Answer 21

Gram positive

Question 22

What are the two layers of the cell wall of gram negative bacteria?

Answer 22

• Outer membrane
• Peptidoglycan layer

Question 23

What allows transport of molecules across the outer membrane of gram-negative bacteria?

Answer 23

Porins

Question 24

What is the function of lipopolysaccharides in the outer membrane of gram-negative bacteria?

Answer 24

Attachment of bacteria to surfaces

Question 25

What is the area of the space between the plasma membrane and the peptidoglycan layer?

Answer 25

Periplasmic space

Question 26

Which type of bacteria (gram positive/negative) require more complex systems for protein secretion? Why?

Answer 26

• Gram negative
• Two layers of cell wall makes it more complicated for proteins to travel into the external environment during secretion, and so a more complex system is needed

Question 27

Which type of bacteria stains which colour under a gram stain?

Answer 27

Gram +ve (like high pH): Purple
Gram e-ve (like low pH): Pink

Question 28

Describe (with adjectives) the cell wall of mycobaceria

Answer 28

Waxy and hydrophobic

Question 29

Describe (with technical terms) the cell wall of mycobacteria

Answer 29

• Plasma membrane
• Peptidoglycan
• Arabinogalactan
• Mycolic acids
• Outer lipid layer

Question 30

Why is a waxy cell wall advantageous for mycobacteria?

Answer 30

• Macrophage resistance
• Tolerates disinfectants

Question 31

What is chemotaxis?

Answer 31

The movement of an organism or entity in response to a chemical stimulus.

Question 32

List three kinds of arrangements of flagella

Answer 32

• Monotrichous
• Lophotrichous
• Peritrichous

Question 33

What are the fine, hair-like protein chains on bacteria called?

Answer 33

• Fimbriae
• Pili

Question 34

How can fimbriae/pili be involved in virulence?

Answer 34

Attachment:
- To other cells (plant or animal)
- To surfaces (prelude to biofilms)

Question 35

What is the function of an F-pilus?

Answer 35

To connect a donor and recipient bacteria during conjugation

Question 36

What is a capsule in the context of bacteria? Does it exist in all bacteria?

Answer 36

Polysaccharide layer that exists beyond the cell wall. It is not in all bacteria, but can be found in both gram positive and negative bacteria.

Question 37

What do capsules protect bacteria from?

Answer 37

• Desiccation (removal of moisture)
• Phagocytosis

Question 38

Give on example of where a capsule gives a bacteria its virulence. How is this useful?

Answer 38

• Without capsule, streptococcus pneumonia is avirulent
• Capsule can be used in vaccine