Module 2: Section 1B

Question 1

2 main groups bacteria are divided into

Answer 1

1. Gram-positive
2. Gram-negative

Question 2

Gram-positive

Answer 2

• Retain the colour of the stain (violet)
• Have a cell wall composed of a thick layer of peptidoglycan

Question 3

Gram-negative

Answer 3

• Lose the colour stain (turn red)
• Have a cell wall with a thin layer of peptidoglycan and an outer membrane

Question 4

Teichoic and lipoteichoic acid - gram-positive bacteria

Answer 4

• Help maintain cell envelope structure
• They anchor the stiff peptidoglycan to the cytoplasmic membrane
• Contribute a net negative charge to the cell wall
• Can be recognized by immune system during infections

Question 5

Small periplasmic space - gram-positive bacteria

Answer 5

• gel-like matrix located between the peptidoglycan layer and cytoplasmic membrane
• Houses enzymes important for assembly and attachment to cell wall
• In gram-positive and negative but much smaller in gram-positive

Question 6

Peptidoglycan (PG) - gram-postive bacteria

Answer 6

• Major component of cell wall in gram-positive bacteria
• Macromolecule complex
• Structure includes: glycan chains, covalent cross links, cleavage sites

Question 7

Large periplasmic space - gram-negative bacteria

Answer 7

• Large in size
• Space occupies 20-40% of total cell volume
• Contains many proteins involved in biosynthesis, assembly of PG and outer membrane components

Question 8

Outer membrane (OM) - gram-negative bacteria

Answer 8

• Asymmetrical bilayer membrane
• Contains: porins, lipoprotein, lipopolysaccharide

Question 9

Porins - OM component

Answer 9

allow passage of nutrients into the cell

Question 10

Lipoprotein - OM component

Answer 10

• Abundant cell wall component
• Links PG to OM

Question 11

Lipopolysaccharide - OM component

Answer 11

• Located in outer leaflet of OM
• Contributes to the net negative charge of the cell wall
• Is highly immunogenic
• Structure contains: O-Antigen, Core, Lipid A

Question 12

O-Antigen

Answer 12

• External to cell
• Accessible for interactions with immune cells

Question 13

Core

Answer 13

• External to membrane but close to surface of the cell
• Cross-links ionically with other components of the membrane

Question 14

Lipid A

Answer 14

• Anchors LPS to the OM
• Is inserted into the outer membrane

Question 15

Step 1 of gram stain procedure

Answer 15

Begin with heat fixed cells

Question 16

Step 2 of gram stain procedure

Answer 16

Flood slide with crystal violet dye for 1 minute

Question 17

Step 3 of gram stain procedure

Answer 17

Add iodine solution for 1 minute

Question 18

Step 4 of gram stain procedure

Answer 18

Wash slide with alcohol for 20 seconds

Question 19

Step 5 of gram stain procedure

Answer 19

Counterstain with safranin

Question 20

Cytoplasmic membrane of bacteria cells

Answer 20

• Consists primarily of phospholipids
• Lack steroid-containing lipids like cholesterol
• Contain hopanoids that help stabilize the membrane and withstand conditions like high temp, low pH and detergents

Question 21

Facilitated diffusion

Answer 21

• Molecules move from an area of high concentration to an area of low concentration via a carrier molecule
• No energy is required

Question 22

Primary active transport

Answer 22

• Molecules move from an area of low concentration to high concentration
• Requires ATP
• Usually use ATP-binding cassette transporter

Question 23

Secondary active transport

Answer 23

Uses the movement of one molecule down its concentration gradient to facilitate the transport of a second molecule against its concentration gradient

Question 24

Group translocation

Answer 24

Organic molecule is transported across the membrane and receives chemical modification

Question 25

Iron uptake

Answer 25

- Bacterial pathogens require iron and it must be taken from the extracellular environment - 2 methods: transferrin method and siderophore method

Question 26

Transferrin method

Answer 26

- steal host’s iron-carrying protein (transferrin) - Requires ATP

Question 27

Siderophore method

Answer 27

- Molecule with a high affinity for iron - Pulls the iron towards the bacteria

Question 28

Inclusion bodies - component of bacterial cytoplasm

Answer 28

- Clumps of misfolded proteins inside bacteria - often formed when making recombinant proteins - Also seen when bacteria are infected by phage

Question 29

Carboxysomes - component of bacterial cytoplasm

Answer 29

- Micro compartments in bacterial cytoplasm containing enzymes involved in carbon fixation

Question 30

Intracytoplasmic membranes - component of bacterial cytoplasm

Answer 30

- Extra cytoplasmic membranes that extend and fold within the cytoplasm - Increase membrane associated surface area - Prominent in photosynthetic bacteria

Question 31

Magnetosomes - component of bacterial cytoplasm

Answer 31

- Structural component found in magnetotactic bacteria - Composed of magnetic mineral crystals and surrounded by a phospholipid bilayer - Allow cells to align and swim along Earth's magnetic field lines

Question 32

Endospores

Answer 32

- Resistant asexual spore that develops inside some bacterial cells - Resistant to drying out and does not require nutrients

Question 33

Step 1 of endospore formation

Answer 33

Vegetative bacterium, a symmetrically dividing cellular form

Question 34

Step 2 of endospore formation

Answer 34

- Asymmetric division results in 2 compartments - Larger compartment is mother cell and smaller compartment is the forespore

Question 35

Step 3 of endospore formation

Answer 35

- Septum walls break down - Mother cell engulfs forespore, creating a cell inside a cell

Question 36

Step 4 of endospore formation

Answer 36

The cortex, a thick layer of peptidoglycan is formed

Question 37

Step 5 of endospore formation

Answer 37

- Coat synthesis begins - The endospore coat is composed of proteins that provide chemical and enzymatic resistance to degradation

Question 38

Step 6 of endospore formation

Answer 38

- Coat synthesis is completed - There is an increase in refractility and heat resistance

Question 39

Step 7 of endospore formation

Answer 39

Lysis of the mother cell liberates the endospore

Question 40

Capsule

Answer 40

- A layer of material firmly attached to an individual bacterium - Masks bacteria from the immune system and antibiotics during infection - Prevent desiccation during transmission from host to host

Question 41

Slime layer

Answer 41

- Consists of diffuse, unorganized material that is easily removed - Masks bacteria from the immune system and antibiotics during infection - Prevent desiccation during transmission from host to host

Question 42

Biofilms

Answer 42

- heterogenous (different organisms) - Important for bacterial colonization of environmental and host surfaces

Question 43

Biofilms in the body

Answer 43

- Can harbour many different bacteria - They are sources of infections - Occur on surfaces like catheters, artificial implants and teeth

Question 44

S-layer

Answer 44

- Glycoprotein component of the cell envelop - Provide protection from the immune system and phage invasion - Increase structural stability of the cell wall

Question 45

2 motility structures in bacteria

Answer 45

1. Flagella 2. Pili

Question 46

Flagella

Answer 46

Used for movement in liquid environments

Question 47

Pili

Answer 47

- Fine-hair like structures - Used for movement on solid surfaces called "twitching" - Pili is very good at adherence to surfaces

Question 48

Sex pili

Answer 48

- Provide a pathway for the exchange of genetic information via conjugation

Question 48

Type IV pili

Answer 48

Allow bacteria to move on solid surfaces bye a mechanism called twitching

Question 49

Peritrichous flagella

Answer 49

- Have flagella surrounding the entire periphery of the cell - Ex: Enterobacteriaceae

Question 50

Single/polar flagella

Answer 50

- One flagella - Ex: Desulfovibrio

Question 51

Lophotrichous flagella

Answer 51

- Tufts of flagella at one end of the bacteria - Ex: Alcaligenes faecalis

Question 52

Bipolar flagella

Answer 52

- Single flagellum at both ends of the bacterium - Ex: Helicobacter hepaticus

Question 53

Bacterial flagella structure

Answer 53

- Are firmly anchored in the cell wall but still able to spin very fast - Part associated with the cell wall is called the basal body