L13 Bacterial Growth and Nutrition

Question 1

Metabolism in bacteria is relevant for what three reasons?

Answer 1

1. Defines the preferred environment of the organism
2. Facilitates identification
3. Reveals methods for killing or suppressing bacteria

Question 2

Bacteria may produce ___, which act by highly diverse molecular mechanisms.

Answer 2

Toxins

Question 3

What are the three specific molecular mechanisms of toxin action?

Answer 3

1. Toxin sits in the membrane
2. Toxin crosses the membrane and disrupts something (eg, protein synthesis)
3. Toxin activates a cell signaling event

Question 4

What is a Type III secretory apparatus?

Answer 4

A protein appendage found in some Gram-negative bacteria; the needle-like structure is used as a sensory probe to detect eukaryotes and secrete proteins that help the bacteria infect them

Question 5

Describe the growth rate of bacteria.

Answer 5

Lag phase (bacteria sense environment and readjust to the new, nutrient rich state; activates genes for production of proteins/metabolism)
Exponential growth phase (hyperbolic)
Stationary growth (dynamic equilibrium)
Death

Question 6

What are the three major factors that affect the growth rate of bacteria?

Answer 6

1. Medium composition
2. Temperature
3. Oxygen

Question 7

What is one therapeutic way to target DNA formation in bacteria?

Answer 7

Inhibit gyrase, an enzyme needed to detangle DNA strands for successful replication

Question 8

What is one therapeutic way to target protein formation in bacteria?

Answer 8

Inhibit ribosome function

Question 9

What are the 3 steps in peptidoglycan synthesis?

Answer 9

1. Glycan is synthesized in the bacterial cytoplasm
2. Molecular machinery moves glycan across the inner membrane to a gap in the pre-existing peptidoglycan
3. Ligation of glycan into this spot

Question 10

What are the 5 major cellular targets of antibiotics?

Answer 10

1. Peptidoglycan synthesis
2. DNA
3. RNA polymerase
4. Ribosome inhibitors
5. Cell membrane

Question 11

What are siderophores?

Answer 11

Small, high-affinity iron-chelating compounds secreted by bacteria to capture iron and bring it into the bacteria via active transport

Question 12

True or false - the genes encoding siderophore systems can be transferred among bacteria.

Answer 12

True

Question 13

What are the two possible metabolic paths for nutrients in bacteria?

Answer 13

Glycolysis –> fermentation (anaerobic)

Glycolysis –> TCA cycle –> respiration

Question 14

Any drug that impairs the inner membrane will destroy respiration. Why?

Answer 14

The relevant enzymes for respiration are found in the inner membrane.

Question 15

Why is it important to know the by-products of fermentation for various bacteria?

Answer 15

Can be helpful for specific diagnoses

Question 16

What enzymes are used during respiration to clear away active oxygen species?

Answer 16

1. Peroxidase (clears H2O2)

2. Superoxide dismutases (clears O2-)

Question 17

Why is important to identify which enzymes are used to detoxify active oxygen in bacteria?

Answer 17

Useful for diagnosis, can be virulence factors, give clues for anitmicrobial agents

Question 18

What is the generic response to starvation in bacteria?

Answer 18

Spore formation

Question 19

What is the generic response to heat in bacteria?

Answer 19

Synthesis of proteins to protect against heat

Question 20

What are two pathogenic-specific stress responses?

Answer 20

1. Release of toxin

2. Pili connection to surfaces

Question 21

Pathogenesis requires precise control of ___ in ___ and ___.

Answer 21

Gene expression; time; space

Question 22

Describe the pathogenesis of vibrio cholerae.

Answer 22

0-1 hours: enters GI tract, senses environment, activates a virulence factor for attachment
2-3 hours: attaches
4+ hours: activates genes for cholera toxin after attachment, disrupts epithelial cell homeostasis

Question 23

Gene regulation is ___.

Answer 23

Hierarchical