Lecture 7 Microbial Growth

Question 1

Solutes such as salts and sugars ____ the availability of water to microbes.

Answer 1

Decrease

Question 2

Availability of ___ affects growth of all cells.

This is expressed as?

Answer 2

Water

water activity (Aw)
ex.) higher [solute] ---> lower Aw

Question 3

Hypotonic Solution

Answer 3

Solute conc. inside (intracellular) > Solute conc. outside (extracellular)

Question 4

Isotonic Solution

Answer 4

Solute conc. inside (intracellular) = Solute conc. outside (extracellular)

Question 5

Hypertonic Solution

Answer 5

Solute conc. inside (intracellular) < Solute conc. outside (extracellular)

Question 6

What is a Halophile?

Name the two examples from lecture.

Answer 6

Osmophiles that live in high[Salt]

ex. ) - Halobacterium (member of the archaea)
- Staphylococcus
- Human skin
- Mannitol Salt Agar used to isolate

Question 7

What are microbes that can grown under pH of 0-6?

Answer 7

Acidophiles

Question 8

What are microbes that can grow under pH of 8-12

Answer 8

Alkaliphiles

Question 9

What is the pH range of Escherichia coli?

Answer 9

pH 2-9 10million fold difference

Question 10

How do Halophiles live in a high salt environment?

Answer 10

They use compatible solutes like KCl. Keeps intracellular solute conc. high with out interfering with growth or metabolism.

Question 11

What are nutrients?

Answer 11

Substances used in biosynthesis and energy release - required for growth.

Question 12

What is 95% of the microbial cell weight made of?

Answer 12

Macronutrients (or macroelemets)

C,O,H,N,S,P,Fe

Question 13

What is the the other 5% of the cell weight made of?

Answer 13

Micronutrients (or trace elements)

Co, Cu, Zn, Mn

Question 14

What is the form of nitrogen that microbes can use?

Answer 14

Ammonia (NH3) or Nitrate (NO3)

Question 15

What is Nitrogen fixation?

Answer 15

N2 reduced to ammonia (NH3)

Question 16

Rhizobium and Azotobacter

Answer 16

Rhizobium - in symbiosis with plants

Azotobacter - free living in soil

Question 17

How does food for microbes enter the cell?

Answer 17

• at high rates
• across membranes
• selective fashion
• often against concentration gradient

Passive and Active transport systems used.

Question 18

Describes Passive Transport

Answer 18

• no energy required

- requires gradient from [higher] to [lower]

Question 19

Passive Diffusion

Answer 19

Only small molecules and certain gases

Question 20

Facilitated Diffusion

Answer 20

• Uses membrane carrier proteins

ex) Aquaporins - form H2O channels

Question 21

Active Transport

Answer 21

• Energy - dependent
• Moves nutrients against gradient
• ATP or proton motive force used

Question 22

Describe Primary Active Transport : ABC Transporters

Answer 22

1. ) After binding solute, the solute-binding protein approaches ABC transporter.
2. ) Solute-binding protein attaches to transporter and releases solute. Energy released by hydrolysis of ATP drives movement of solute across membrane.

Question 23

different types of ABC Transporters

Answer 23

• Uptake ABC - move nutrients in
• Export ABC - also called Multidrug Efflux Pumps, moves substances out
• In bacterial cells - move antibiotics out, bacteria become resistant to antibiotic
• In cancer cells - move anticancer drugs out, tumor becomes resistant

Question 24

Describe Secondary Active Transport and name the example from lecture.

Answer 24

• Uses potential energy of ion gradients
• Electron transport across membrane generates proton (H+) gradient
• Can use gradient to do work !

Example Lac Permease
- Membrane protein, moves lactose in powered by proton also moving in

Question 25

Active Transport : Group Translocation and name the example from lecture.

Answer 25

- Nutrient chemically altered - Energy from phosphoenolpyruvate attaches P to sugars - Phosphoenolpyruvate - key intermediate in Glycolysis - Metabolic pathway that converts glucose to pyruvate REVIEW FIG. 3.14

Question 26

Describe Iron Uptake

Answer 26

- Microbes release siderophores to acquire Fr

Question 27

What are Siderophores and name the example from lecture

Answer 27

- Fe complex then transported into cell often using ABC Enterobactin : An Escherichia coli siderophore

Question 28

Describe Siderophore-iron complex transport into a gram - negative bacterial cell.

Answer 28

1. ) E. coli synthesizes and secretes an iron-binding enterochelin that bind Fe3+ 2a. ) The complex is transported to the periplasm through an outer membrane protein (FepA) and is transported into the cell by an ABC transporter that includes a periplasmic solute-binding protein (FepB) and the integral membrane proteins FepC, G, and D. 3. ) Inside the cell, the iron is released and reduced to Fe2+

Question 29

What is Metabolism

Answer 29

All the chemical reactions in a cell

Question 30

What Catabolism

Answer 30

Breakdown of complex molecules into smaller ones with release of benefit for Anabolism - reactions that build cells.